[commit] Better error message for invalid hoisting

We're already tracking which variables are hoisted context variables, so if we see a mutation of a frozen value we can emit a custom error message to help users identify the problem.

.codesandbox/ci.json

@@ -1,10 +1,11 @@
 {
-  "packages": ["packages/react", "packages/react-dom", "packages/scheduler"],
+  "packages": ["packages/react", "packages/react-dom", "packages/react-server-dom-webpack", "packages/scheduler"],
   "buildCommand": "download-build-in-codesandbox-ci",
   "node": "18",
   "publishDirectory": {
     "react": "build/oss-experimental/react",
     "react-dom": "build/oss-experimental/react-dom",
+    "react-server-dom-webpack": "build/oss-experimental/react-server-dom-webpack",
     "scheduler": "build/oss-experimental/scheduler"
   },
   "sandboxes": ["new"],

.eslintrc.js

@@ -496,6 +496,7 @@ module.exports = {
         'packages/react-devtools-shared/src/devtools/views/**/*.js',
         'packages/react-devtools-shared/src/hook.js',
         'packages/react-devtools-shared/src/backend/console.js',
+        'packages/react-devtools-shared/src/backend/fiber/renderer.js',
         'packages/react-devtools-shared/src/backend/shared/DevToolsComponentStackFrame.js',
         'packages/react-devtools-shared/src/frontend/utils/withPermissionsCheck.js',
       ],
@@ -504,6 +505,7 @@ module.exports = {
         __IS_FIREFOX__: 'readonly',
         __IS_EDGE__: 'readonly',
         __IS_NATIVE__: 'readonly',
+        __IS_INTERNAL_MCP_BUILD__: 'readonly',
         __IS_INTERNAL_VERSION__: 'readonly',
         chrome: 'readonly',
       },
@@ -559,6 +561,7 @@ module.exports = {
     ConsoleTask: 'readonly', // TOOD: Figure out what the official name of this will be.
     ReturnType: 'readonly',
     AnimationFrameID: 'readonly',
+    WeakRef: 'readonly',
     // For Flow type annotation. Only `BigInt` is valid at runtime.
     bigint: 'readonly',
     BigInt: 'readonly',
@@ -579,6 +582,7 @@ module.exports = {
     JSONValue: 'readonly',
     JSResourceReference: 'readonly',
     MouseEventHandler: 'readonly',
+    NavigateEvent: 'readonly',
     PropagationPhases: 'readonly',
     PropertyDescriptor: 'readonly',
     React$AbstractComponent: 'readonly',
@@ -608,6 +612,7 @@ module.exports = {
     TimeoutID: 'readonly',
     WheelEventHandler: 'readonly',
     FinalizationRegistry: 'readonly',
+    Exclude: 'readonly',
     Omit: 'readonly',
     Keyframe: 'readonly',
     PropertyIndexedKeyframes: 'readonly',
@@ -615,6 +620,8 @@ module.exports = {
     GetAnimationsOptions: 'readonly',
     Animatable: 'readonly',
     ScrollTimeline: 'readonly',
+    EventListenerOptionsOrUseCapture: 'readonly',
+    FocusOptions: 'readonly',
 
     spyOnDev: 'readonly',
     spyOnDevAndProd: 'readonly',
@@ -632,5 +639,6 @@ module.exports = {
     AsyncLocalStorage: 'readonly',
     async_hooks: 'readonly',
     globalThis: 'readonly',
+    navigation: 'readonly',
   },
 };

.github/ISSUE_TEMPLATE/19.md

@@ -1,18 +0,0 @@
----
-name: "⚛React 19 beta issue"
-about: Report a issue with React 19 beta.
-title: '[React 19]'
-labels: 'React 19'
-
----
-
-
-## Summary
-
-<!--
-  Please provide a CodeSandbox (https://codesandbox.io/s/new), a link to a
-  repository on GitHub, or provide a minimal code example that reproduces the
-  problem. You may provide a screenshot of the application if you think it is
-  relevant to your bug report. Here are some tips for providing a minimal
-  example: https://stackoverflow.com/help/mcve.
--->

.github/workflows/compiler_discord_notify.yml

@@ -7,9 +7,28 @@ on:
       - compiler/**
       - .github/workflows/compiler_**.yml
 
+permissions: {}
+
 jobs:
+  check_access:
+    if: ${{ github.event.pull_request.draft == false }}
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - run: echo ${{ github.event.pull_request.author_association }}
+      - name: Check is member or collaborator
+        id: check_is_member_or_collaborator
+        if: ${{ github.event.pull_request.author_association == 'MEMBER' || github.event.pull_request.author_association == 'COLLABORATOR' }}
+        run: echo "is_member_or_collaborator=true" >> "$GITHUB_OUTPUT"
+
   check_maintainer:
+    if: ${{ needs.check_access.outputs.is_member_or_collaborator == 'true' || needs.check_access.outputs.is_member_or_collaborator == true }}
+    needs: [check_access]
     uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
+    permissions:
+      # Used by check_maintainer
+      contents: read
     with:
       actor: ${{ github.event.pull_request.user.login }}
 

.github/workflows/compiler_playground.yml

@@ -8,6 +8,8 @@ on:
       - compiler/**
       - .github/workflows/compiler_playground.yml
 
+permissions: {}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.run_id }}
   cancel-in-progress: true
@@ -38,9 +40,25 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-and-playground-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+        working-directory: compiler
+      - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Check Playwright version
+        id: playwright_version
+        run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"
+      - name: Cache Playwright Browsers for version ${{ steps.playwright_version.outputs.playwright_version }}
+        id: cache_playwright_browsers
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/ms-playwright
+          key: playwright-browsers-v6-${{ runner.arch }}-${{ runner.os }}-${{ steps.playwright_version.outputs.playwright_version }}
       - run: npx playwright install --with-deps chromium
+        if: steps.cache_playwright_browsers.outputs.cache-hit != 'true'
+      - run: npx playwright install-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit == 'true'
       - run: CI=true yarn test
       - run: ls -R test-results
         if: '!cancelled()'
@@ -50,3 +68,4 @@ jobs:
         with:
           name: test-results
           path: compiler/apps/playground/test-results
+          if-no-files-found: ignore

.github/workflows/compiler_prereleases.yml

@@ -16,15 +16,19 @@ on:
       version_name:
         required: true
         type: string
+      tag_version:
+        required: false
+        type: string
     secrets:
       NPM_TOKEN:
         required: true
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
   SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
-  GH_TOKEN: ${{ github.token }}
   NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
 
 defaults:
@@ -48,9 +52,10 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Publish packages to npm
         run: |
           cp ./scripts/release/ci-npmrc ~/.npmrc
-          scripts/release/publish.js --frfr --ci --versionName=${{ inputs.version_name }} --tag ${{ inputs.dist_tag }}
+          scripts/release/publish.js --frfr --ci --versionName=${{ inputs.version_name }} --tag=${{ inputs.dist_tag }} ${{ inputs.tag_version && format('--tagVersion={0}', inputs.tag_version) || '' }}

.github/workflows/compiler_prereleases_manual.yml

@@ -14,6 +14,11 @@ on:
       version_name:
         required: true
         type: string
+      tag_version:
+        required: false
+        type: string
+
+permissions: {}
 
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
@@ -27,5 +32,6 @@ jobs:
       release_channel: ${{ inputs.release_channel }}
       dist_tag: ${{ inputs.dist_tag }}
       version_name: ${{ inputs.version_name }}
+      tag_version: ${{ inputs.tag_version }}
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

.github/workflows/compiler_prereleases_nightly.yml

@@ -5,6 +5,8 @@ on:
     # At 10 minutes past 16:00 on Mon, Tue, Wed, Thu, and Fri
     - cron: 10 16 * * 1,2,3,4,5
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 

.github/workflows/compiler_prereleases_weekly.yml

@@ -1,21 +0,0 @@
-name: (Compiler) Publish Prereleases Weekly
-
-on:
-  schedule:
-    # At 10 minutes past 9:00 on Mon
-    - cron: 10 9 * * 1
-
-env:
-  TZ: /usr/share/zoneinfo/America/Los_Angeles
-
-jobs:
-  publish_prerelease_beta:
-    name: Publish to beta channel
-    uses: facebook/react/.github/workflows/compiler_prereleases.yml@main
-    with:
-      commit_sha: ${{ github.sha }}
-      release_channel: beta
-      dist_tag: beta
-      version_name: '19.0.0'
-    secrets:
-      NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

.github/workflows/compiler_typescript.yml

@@ -8,6 +8,8 @@ on:
       - compiler/**
       - .github/workflows/compiler_typescript.yml
 
+permissions: {}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.run_id }}
   cancel-in-progress: true
@@ -45,11 +47,13 @@ jobs:
           cache-dependency-path: compiler/yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn workspace babel-plugin-react-compiler lint
 
   # Hardcoded to improve parallelism
@@ -69,8 +73,9 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn workspace babel-plugin-react-compiler jest
 
   test:
@@ -94,8 +99,9 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/**/yarn.lock') }}
+          key: compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('compiler/yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: xvfb-run -a yarn workspace ${{ matrix.workspace_name }} test
         if: runner.os == 'Linux' && matrix.workspace_name == 'react-forgive'
       - run: yarn workspace ${{ matrix.workspace_name }} test

.github/workflows/devtools_regression_tests.yml

@@ -9,6 +9,8 @@ on:
         required: false
         type: string
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
@@ -18,6 +20,9 @@ jobs:
   download_build:
     name: Download base build
     runs-on: ubuntu-latest
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -35,7 +40,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Download react-devtools artifacts for base revision
         run: |
           git fetch origin main
@@ -47,6 +54,7 @@ jobs:
         with:
           name: build
           path: build
+          if-no-files-found: error
 
   build_devtools_and_process_artifacts:
     name: Build DevTools and process artifacts
@@ -69,6 +77,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore archived build
         uses: actions/download-artifact@v4
         with:
@@ -84,17 +93,20 @@ jobs:
         with:
           name: react-devtools
           path: build/devtools.tgz
+          if-no-files-found: error
       # Simplifies getting the extension for local testing
       - name: Archive chrome extension
         uses: actions/upload-artifact@v4
         with:
           name: react-devtools-chrome-extension
           path: build/devtools/chrome-extension.zip
+          if-no-files-found: error
       - name: Archive firefox extension
         uses: actions/upload-artifact@v4
         with:
           name: react-devtools-firefox-extension
           path: build/devtools/firefox-extension.zip
+          if-no-files-found: error
 
   run_devtools_tests_for_versions:
     name: Run DevTools tests for versions
@@ -125,6 +137,7 @@ jobs:
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore all archived build artifacts
         uses: actions/download-artifact@v4
       - name: Display structure of build
@@ -160,14 +173,24 @@ jobs:
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore all archived build artifacts
         uses: actions/download-artifact@v4
       - name: Display structure of build
         run: ls -R build
-      - name: Playwright install deps
-        run: |
-          npx playwright install
-          sudo npx playwright install-deps
+      - name: Check Playwright version
+        id: playwright_version
+        run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"
+      - name: Cache Playwright Browsers for version ${{ steps.playwright_version.outputs.playwright_version }}
+        id: cache_playwright_browsers
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/ms-playwright
+          key: playwright-browsers-v6-${{ runner.arch }}-${{ runner.os }}-${{ steps.playwright_version.outputs.playwright_version }}
+      - run: npx playwright install --with-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit != 'true'
+      - run: npx playwright install-deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit == 'true'
       - run: ./scripts/ci/download_devtools_regression_build.js ${{ matrix.version }}
       - run: ls -R build-regression
       - run: ./scripts/ci/run_devtools_e2e_tests.js ${{ matrix.version }}
@@ -179,3 +202,4 @@ jobs:
         with:
           name: screenshots
           path: ./tmp/screenshots
+          if-no-files-found: warn

.github/workflows/runtime_build_and_test.yml

@@ -7,6 +7,8 @@ on:
     paths-ignore:
       - compiler/**
 
+permissions: {}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.run_id }}
   cancel-in-progress: true
@@ -41,6 +43,16 @@ jobs:
           node-version-file: '.nvmrc'
           cache: yarn
           cache-dependency-path: yarn.lock
+      - name: Warm with old cache
+        if: steps.node_modules.outputs.cache-hit != 'true'
+        uses: actions/cache/restore@v4
+        with:
+          path: |
+            **/node_modules
+          key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - run: yarn install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Save cache
@@ -74,6 +86,16 @@ jobs:
           cache-dependency-path: |
             yarn.lock
             compiler/yarn.lock
+      - name: Warm with old cache
+        if: steps.node_modules.outputs.cache-hit != 'true'
+        uses: actions/cache/restore@v4
+        with:
+          path: |
+            **/node_modules
+          key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          restore-keys: |
+            runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
       - run: yarn install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd compiler install --frozen-lockfile
@@ -127,6 +149,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -154,6 +179,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -241,6 +269,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          restore-keys: |
+            runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -249,6 +280,35 @@ jobs:
         if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn test ${{ matrix.params }} --ci --shard=${{ matrix.shard }}
 
+  # Hardcoded to improve parallelism
+  test-linter:
+    name: Test eslint-plugin-react-hooks
+    needs: [runtime_compiler_node_modules_cache]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: '.nvmrc'
+          cache: yarn
+          cache-dependency-path:  |
+            yarn.lock
+            compiler/yarn.lock
+      - name: Restore cached node_modules
+        uses: actions/cache@v4
+        id: node_modules
+        with:
+          path: |
+            **/node_modules
+          key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          restore-keys: |
+            runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
+      - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: ./scripts/react-compiler/build-compiler.sh && ./scripts/react-compiler/link-compiler.sh
+      - run: yarn workspace eslint-plugin-react-hooks test
+        
   # ----- BUILD -----
   build_and_lint:
     name: yarn build and lint
@@ -282,6 +342,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          restore-keys: |
+            runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -302,6 +365,7 @@ jobs:
         with:
           name: _build_${{ matrix.worker_id }}_${{ matrix.release_channel }}
           path: build
+          if-no-files-found: error
 
   test_build:
     name: yarn test-build
@@ -340,9 +404,16 @@ jobs:
           # TODO: Test more persistent configurations?
         ]
         shard:
-          - 1/3
-          - 2/3
-          - 3/3
+          - 1/10
+          - 2/10
+          - 3/10
+          - 4/10
+          - 5/10
+          - 6/10
+          - 7/10
+          - 8/10
+          - 9/10
+          - 10/10
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -362,6 +433,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          restore-keys: |
+            runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -381,6 +455,10 @@ jobs:
   process_artifacts_combined:
     name: Process artifacts combined
     needs: [build_and_lint, runtime_node_modules_cache]
+    permissions:
+      # https://github.com/actions/attest-build-provenance
+      id-token: write
+      attestations: write
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -398,6 +476,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -420,12 +501,25 @@ jobs:
         # TODO: Migrate scripts to use `build` directory instead of `build2`
       - run: cp ./build.tgz ./build2.tgz
       - name: Archive build artifacts
+        id: upload_artifacts_combined
         uses: actions/upload-artifact@v4
         with:
           name: artifacts_combined
           path: |
             ./build.tgz
             ./build2.tgz
+          if-no-files-found: error
+      - uses: actions/attest-build-provenance@v2
+        # We don't verify builds generated from pull requests not originating from facebook/react.
+        # However, if the PR lands, the run on `main` will generate the attestation which can then
+        # be used to download a build via scripts/release/download-experimental-build.js.
+        #
+        # Note that this means that scripts/release/download-experimental-build.js must be run with
+        # --no-verify when downloading a build from a fork.
+        if: github.event_name == 'push' && github.ref_name == 'main' || github.event.pull_request.head.repo.full_name == github.repository
+        with:
+          subject-name: artifacts_combined.zip
+          subject-digest: sha256:${{ steps.upload_artifacts_combined.outputs.artifact-digest }}
 
   check_error_codes:
     name: Search build artifacts for unminified errors
@@ -447,6 +541,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -484,6 +581,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -517,7 +617,7 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: fixtures_dom-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          key: fixtures_dom-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'fixtures/dom/yarn.lock') }}
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn --cwd fixtures/dom install --frozen-lockfile
@@ -561,11 +661,26 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: fixtures_flight-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          key: fixtures_flight-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'fixtures/flight/yarn.lock') }}
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: yarn --cwd fixtures/flight install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Check Playwright version
+        id: playwright_version
+        run: echo "playwright_version=$(npm ls @playwright/test | grep @playwright | sed 's/.*@//' | head -1)" >> "$GITHUB_OUTPUT"
+      - name: Cache Playwright Browsers for version ${{ steps.playwright_version.outputs.playwright_version }}
+        id: cache_playwright_browsers
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/ms-playwright
+          key: playwright-browsers-v6-${{ runner.arch }}-${{ runner.os }}-${{ steps.playwright_version.outputs.playwright_version }}
+      - name: Playwright install deps
+        if: steps.cache_playwright_browsers.outputs.cache-hit != 'true'
+        working-directory: fixtures/flight
+        run: npx playwright install --with-deps chromium
       - name: Restore archived build
         uses: actions/download-artifact@v4
         with:
@@ -574,16 +689,6 @@ jobs:
           merge-multiple: true
       - name: Display structure of build
         run: ls -R build
-      - name: Install fixture dependencies
-        working-directory: fixtures/flight
-        run: |
-          yarn install --frozen-lockfile --cache-folder ~/.cache/yarn
-          if [ $? -ne 0 ]; then
-            yarn install --frozen-lockfile --cache-folder ~/.cache/yarn
-          fi
-      - name: Playwright install deps
-        working-directory: fixtures/flight
-        run: npx playwright install --with-deps chromium
       - name: Run tests
         working-directory: fixtures/flight
         run: yarn test
@@ -595,11 +700,13 @@ jobs:
         with:
           name: flight-playwright-report
           path: fixtures/flight/playwright-report
+          if-no-files-found: warn
       - name: Archive Flight fixture artifacts
         uses: actions/upload-artifact@v4
         with:
           name: flight-test-results
           path: fixtures/flight/test-results
+          if-no-files-found: ignore
 
   # ----- DEVTOOLS -----
   build_devtools_and_process_artifacts:
@@ -626,6 +733,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -647,6 +757,7 @@ jobs:
         with:
           name: react-devtools-${{ matrix.browser }}-extension
           path: build/devtools/${{ matrix.browser }}-extension.zip
+          if-no-files-found: error
 
   merge_devtools_artifacts:
     name: Merge DevTools artifacts
@@ -679,6 +790,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -700,7 +814,10 @@ jobs:
   sizebot:
     if: ${{ github.event_name == 'pull_request' && github.ref_name != 'main' && github.event.pull_request.base.ref == 'main' }}
     name: Run sizebot
-    needs: [build_and_lint, runtime_node_modules_cache]
+    needs: [build_and_lint]
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -712,7 +829,7 @@ jobs:
           cache: yarn
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
-        uses: actions/cache/restore@v4
+        uses: actions/cache@v4 # note: this does not reuse centralized cache since it has unique cache key
         id: node_modules
         with:
           path: |
@@ -725,21 +842,23 @@ jobs:
       - run: yarn --cwd scripts/release install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Download artifacts for base revision
+        # The build could have been generated from a fork, so we must download the build without
+        # any verification. This is safe since we only use this for sizebot calculation and the
+        # unverified artifact is not used. Additionally this workflow runs in the pull_request
+        # trigger so only restricted permissions are available.
         run: |
-          GH_TOKEN=${{ github.token }} scripts/release/download-experimental-build.js --commit=$(git rev-parse ${{ github.event.pull_request.base.sha }})
+          GH_TOKEN=${{ github.token }} scripts/release/download-experimental-build.js --commit=$(git rev-parse ${{ github.event.pull_request.base.sha }}) ${{ (github.event.pull_request.head.repo.full_name != github.repository && '--noVerify') || ''}}
           mv ./build ./base-build
-      # TODO: The `download-experimental-build` script copies the npm
-      # packages into the `node_modules` directory. This is a historical
-      # quirk of how the release script works. Let's pretend they
-      # don't exist.
       - name: Delete extraneous files
+        # TODO: The `download-experimental-build` script copies the npm
+        # packages into the `node_modules` directory. This is a historical
+        # quirk of how the release script works. Let's pretend they
+        # don't exist.
         run: rm -rf ./base-build/node_modules
       - name: Display structure of base-build from origin/main
         run: ls -R base-build
       - name: Ensure clean build directory
         run: rm -rf build
-      - run: yarn install --frozen-lockfile
-        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Restore archived build for PR
         uses: actions/download-artifact@v4
         with:
@@ -759,3 +878,4 @@ jobs:
         with:
           name: sizebot-message
           path: sizebot-message.md
+          if-no-files-found: ignore

.github/workflows/runtime_commit_artifacts.yml

@@ -22,6 +22,8 @@ on:
         default: false
         type: boolean
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
@@ -30,6 +32,40 @@ env:
 jobs:
   download_artifacts:
     runs-on: ubuntu-latest
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
+    steps:
+      - uses: actions/checkout@v4
+      - name: Restore cached node_modules
+        uses: actions/cache@v4
+        id: node_modules
+        with:
+          path: |
+            **/node_modules
+          key: runtime-release-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'scripts/release/yarn.lock') }}
+      - name: Ensure clean build directory
+        run: rm -rf build
+      - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Download artifacts for base revision
+        run: |
+          GH_TOKEN=${{ github.token }} scripts/release/download-experimental-build.js --commit=${{ inputs.commit_sha || github.event.workflow_run.head_sha || github.sha }}
+      - name: Display structure of build
+        run: ls -R build
+      - name: Archive build
+        uses: actions/upload-artifact@v4
+        with:
+          name: build
+          path: build/
+          if-no-files-found: error
+
+
+  process_artifacts:
+    runs-on: ubuntu-latest
+    needs: [download_artifacts]
     outputs:
       www_branch_count: ${{ steps.check_branches.outputs.www_branch_count }}
       fbsource_branch_count: ${{ steps.check_branches.outputs.fbsource_branch_count }}
@@ -69,25 +105,11 @@ jobs:
         run: |
           echo "www_branch_count=$(git ls-remote --heads origin "refs/heads/meta-www" | wc -l)" >> "$GITHUB_OUTPUT"
           echo "fbsource_branch_count=$(git ls-remote --heads origin "refs/heads/meta-fbsource" | wc -l)" >> "$GITHUB_OUTPUT"
-      - uses: actions/setup-node@v4
+      - name: Restore downloaded build
+        uses: actions/download-artifact@v4
         with:
-          node-version-file: '.nvmrc'
-          cache: yarn
-          cache-dependency-path: yarn.lock
-      - name: Restore cached node_modules
-        uses: actions/cache@v4
-        id: node_modules
-        with:
-          path: |
-            **/node_modules
-          key: runtime-release-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'scripts/release/yarn.lock') }}
-      - name: Ensure clean build directory
-        run: rm -rf build
-      - run: yarn install --frozen-lockfile
-      - run: yarn --cwd scripts/release install --frozen-lockfile
-      - name: Download artifacts for base revision
-        run: |
-          GH_TOKEN=${{ github.token }} scripts/release/download-experimental-build.js --commit=${{ inputs.commit_sha || github.event.workflow_run.head_sha || github.sha }}
+          name: build
+          path: build
       - name: Display structure of build
         run: ls -R build
       - name: Strip @license from eslint plugin and react-refresh
@@ -110,9 +132,9 @@ jobs:
           mkdir ./compiled/facebook-www/__test_utils__
           mv build/__test_utils__/ReactAllWarnings.js ./compiled/facebook-www/__test_utils__/ReactAllWarnings.js
 
-          # Move eslint-plugin-react-hooks into eslint-plugin-react-hooks
+          # Copy eslint-plugin-react-hooks
           mkdir ./compiled/eslint-plugin-react-hooks
-          mv build/oss-experimental/eslint-plugin-react-hooks/cjs/eslint-plugin-react-hooks.development.js \
+          cp build/oss-experimental/eslint-plugin-react-hooks/cjs/eslint-plugin-react-hooks.development.js \
             ./compiled/eslint-plugin-react-hooks/index.js
 
           # Move unstable_server-external-runtime.js into facebook-www
@@ -145,15 +167,21 @@ jobs:
           rm $RENDERER_FOLDER/ReactFabric-{dev,prod,profiling}.js
           rm $RENDERER_FOLDER/ReactNativeRenderer-{dev,prod,profiling}.js
 
+          # Copy eslint-plugin-react-hooks
+          # NOTE: This is different from www, here we include the full package
+          #       including package.json to include dependencies in fbsource.
+          mkdir "$BASE_FOLDER/tools"
+          cp -r build/oss-experimental/eslint-plugin-react-hooks "$BASE_FOLDER/tools"
+
           # Move React Native version file
           mv build/facebook-react-native/VERSION_NATIVE_FB ./compiled-rn/VERSION_NATIVE_FB
 
           ls -R ./compiled-rn
       - name: Add REVISION files
         run: |
-          echo ${{ github.sha }} >> ./compiled/facebook-www/REVISION
+          echo ${{ inputs.commit_sha || github.event.workflow_run.head_sha || github.sha }} >> ./compiled/facebook-www/REVISION
           cp ./compiled/facebook-www/REVISION ./compiled/facebook-www/REVISION_TRANSFORMS
-          echo ${{ github.sha}} >> ./compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/REVISION
+          echo ${{ inputs.commit_sha || github.event.workflow_run.head_sha || github.sha }} >> ./compiled-rn/facebook-fbsource/xplat/js/react-native-github/Libraries/Renderer/REVISION
       - name: "Get current version string"
         id: get_current_version
         run: |
@@ -170,15 +198,20 @@ jobs:
         with:
           name: compiled
           path: compiled/
+          if-no-files-found: error
       - uses: actions/upload-artifact@v4
         with:
           name: compiled-rn
           path: compiled-rn/
+          if-no-files-found: error
 
   commit_www_artifacts:
-    needs: download_artifacts
-    if: inputs.force == true || (github.ref == 'refs/heads/main' && needs.download_artifacts.outputs.www_branch_count == '0')
+    needs: [download_artifacts, process_artifacts]
+    if: inputs.force == true || (github.ref == 'refs/heads/main' && needs.process_artifacts.outputs.www_branch_count == '0')
     runs-on: ubuntu-latest
+    permissions:
+      # Used to push a commit to builds/facebook-www
+      contents: write
     steps:
       - uses: actions/checkout@v4
         with:
@@ -190,12 +223,12 @@ jobs:
           name: compiled
           path: compiled/
       - name: Revert version changes
-        if: needs.download_artifacts.outputs.last_version_classic != '' && needs.download_artifacts.outputs.last_version_modern != ''
+        if: needs.process_artifacts.outputs.last_version_classic != '' && needs.process_artifacts.outputs.last_version_modern != ''
         env:
-          CURRENT_VERSION_CLASSIC: ${{ needs.download_artifacts.outputs.current_version_classic }}
-          CURRENT_VERSION_MODERN: ${{ needs.download_artifacts.outputs.current_version_modern }}
-          LAST_VERSION_CLASSIC: ${{ needs.download_artifacts.outputs.last_version_classic }}
-          LAST_VERSION_MODERN: ${{ needs.download_artifacts.outputs.last_version_modern }}
+          CURRENT_VERSION_CLASSIC: ${{ needs.process_artifacts.outputs.current_version_classic }}
+          CURRENT_VERSION_MODERN: ${{ needs.process_artifacts.outputs.current_version_modern }}
+          LAST_VERSION_CLASSIC: ${{ needs.process_artifacts.outputs.last_version_classic }}
+          LAST_VERSION_MODERN: ${{ needs.process_artifacts.outputs.last_version_modern }}
         run: |
           echo "Reverting $CURRENT_VERSION_CLASSIC to $LAST_VERSION_CLASSIC"
           grep -rl "$CURRENT_VERSION_CLASSIC" ./compiled || echo "No files found with $CURRENT_VERSION_CLASSIC"
@@ -225,12 +258,12 @@ jobs:
             echo "should_commit=false" >> "$GITHUB_OUTPUT"
           fi
       - name: Re-apply version changes
-        if: inputs.force == true || (steps.check_should_commit.outputs.should_commit == 'true' && needs.download_artifacts.outputs.last_version_classic != '' && needs.download_artifacts.outputs.last_version_modern != '')
+        if: inputs.force == true || (steps.check_should_commit.outputs.should_commit == 'true' && needs.process_artifacts.outputs.last_version_classic != '' && needs.process_artifacts.outputs.last_version_modern != '')
         env:
-          CURRENT_VERSION_CLASSIC: ${{ needs.download_artifacts.outputs.current_version_classic }}
-          CURRENT_VERSION_MODERN: ${{ needs.download_artifacts.outputs.current_version_modern }}
-          LAST_VERSION_CLASSIC: ${{ needs.download_artifacts.outputs.last_version_classic }}
-          LAST_VERSION_MODERN: ${{ needs.download_artifacts.outputs.last_version_modern }}
+          CURRENT_VERSION_CLASSIC: ${{ needs.process_artifacts.outputs.current_version_classic }}
+          CURRENT_VERSION_MODERN: ${{ needs.process_artifacts.outputs.current_version_modern }}
+          LAST_VERSION_CLASSIC: ${{ needs.process_artifacts.outputs.last_version_classic }}
+          LAST_VERSION_MODERN: ${{ needs.process_artifacts.outputs.last_version_modern }}
         run: |
           echo "Re-applying $LAST_VERSION_CLASSIC to $CURRENT_VERSION_CLASSIC"
           grep -rl "$LAST_VERSION_CLASSIC" ./compiled || echo "No files found with $LAST_VERSION_CLASSIC"
@@ -244,8 +277,8 @@ jobs:
       - name: Will commit these changes
         if: inputs.force == true || steps.check_should_commit.outputs.should_commit == 'true'
         run: |
-          echo ":"
-          git status -u
+          git add .
+          git status
       - name: Check commit message
         if: inputs.dry_run
         run: |
@@ -264,8 +297,11 @@ jobs:
         run: git push
 
   commit_fbsource_artifacts:
-    needs: download_artifacts
-    if: inputs.force == true || (github.ref == 'refs/heads/main' && needs.download_artifacts.outputs.fbsource_branch_count == '0')
+    needs: [download_artifacts, process_artifacts]
+    permissions:
+      # Used to push a commit to builds/facebook-fbsource
+      contents: write
+    if: inputs.force == true || (github.ref == 'refs/heads/main' && needs.process_artifacts.outputs.fbsource_branch_count == '0')
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -278,10 +314,10 @@ jobs:
           name: compiled-rn
           path: compiled-rn/
       - name: Revert version changes
-        if: needs.download_artifacts.outputs.last_version_rn != ''
+        if: needs.process_artifacts.outputs.last_version_rn != ''
         env:
-          CURRENT_VERSION: ${{ needs.download_artifacts.outputs.current_version_rn }}
-          LAST_VERSION: ${{ needs.download_artifacts.outputs.last_version_rn }}
+          CURRENT_VERSION: ${{ needs.process_artifacts.outputs.current_version_rn }}
+          LAST_VERSION: ${{ needs.process_artifacts.outputs.last_version_rn }}
         run: |
           echo "Reverting $CURRENT_VERSION to $LAST_VERSION"
           grep -rl "$CURRENT_VERSION" ./compiled-rn || echo "No files found with $CURRENT_VERSION"
@@ -296,10 +332,10 @@ jobs:
           git --no-pager diff -U0 --cached | grep '^[+-]' | head -n 100
           echo "===================="
           # Ignore REVISION or lines removing @generated headers.
-          if git diff --cached ':(exclude)*REVISION' | grep -vE "^(@@|diff|index|\-\-\-|\+\+\+|\- \* @generated SignedSource)" | grep "^[+-]" > /dev/null; then
+          if git diff --cached ':(exclude)*REVISION' ':(exclude)*/eslint-plugin-react-hooks/package.json' | grep -vE "^(@@|diff|index|\-\-\-|\+\+\+|\- \* @generated SignedSource)" | grep "^[+-]" > /dev/null; then
             echo "Changes detected"
             echo "===== Changes ====="
-            git --no-pager diff --cached ':(exclude)*REVISION' | grep -vE "^(@@|diff|index|\-\-\-|\+\+\+|\- \* @generated SignedSource)" | grep "^[+-]" | head -n 50
+            git --no-pager diff --cached ':(exclude)*REVISION' ':(exclude)*/eslint-plugin-react-hooks/package.json' | grep -vE "^(@@|diff|index|\-\-\-|\+\+\+|\- \* @generated SignedSource)" | grep "^[+-]" | head -n 50
             echo "==================="
             echo "should_commit=true" >> "$GITHUB_OUTPUT"
           else
@@ -307,10 +343,10 @@ jobs:
             echo "should_commit=false" >> "$GITHUB_OUTPUT"
           fi
       - name: Re-apply version changes
-        if: inputs.force == true || (steps.check_should_commit.outputs.should_commit == 'true' && needs.download_artifacts.outputs.last_version_rn != '')
+        if: inputs.force == true || (steps.check_should_commit.outputs.should_commit == 'true' && needs.process_artifacts.outputs.last_version_rn != '')
         env:
-          CURRENT_VERSION: ${{ needs.download_artifacts.outputs.current_version_rn }}
-          LAST_VERSION: ${{ needs.download_artifacts.outputs.last_version_rn }}
+          CURRENT_VERSION: ${{ needs.process_artifacts.outputs.current_version_rn }}
+          LAST_VERSION: ${{ needs.process_artifacts.outputs.last_version_rn }}
         run: |
           echo "Re-applying $LAST_VERSION to $CURRENT_VERSION"
           grep -rl "$LAST_VERSION" ./compiled-rn || echo "No files found with $LAST_VERSION"

.github/workflows/runtime_discord_notify.yml

@@ -7,9 +7,28 @@ on:
       - compiler/**
       - .github/workflows/compiler_**.yml
 
+permissions: {}
+
 jobs:
+  check_access:
+    if: ${{ github.event.pull_request.draft == false }}
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - run: echo ${{ github.event.pull_request.author_association }}
+      - name: Check is member or collaborator
+        id: check_is_member_or_collaborator
+        if: ${{ github.event.pull_request.author_association == 'MEMBER' || github.event.pull_request.author_association == 'COLLABORATOR' }}
+        run: echo "is_member_or_collaborator=true" >> "$GITHUB_OUTPUT"
+
   check_maintainer:
+    if: ${{ needs.check_access.outputs.is_member_or_collaborator == 'true' || needs.check_access.outputs.is_member_or_collaborator == true }}
+    needs: [check_access]
     uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
+    permissions:
+      # Used by check_maintainer
+      contents: read
     with:
       actor: ${{ github.event.pull_request.user.login }}
 

.github/workflows/runtime_eslint_plugin_e2e.yml

@@ -7,6 +7,8 @@ on:
     paths-ignore:
       - compiler/**
 
+permissions: {}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.run_id }}
   cancel-in-progress: true
@@ -44,17 +46,20 @@ jobs:
         with:
           path: |
             **/node_modules
-          key: runtime-and-compiler-eslint_e2e-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          key: runtime-and-compiler-eslint_e2e-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock', 'fixtures/eslint-v*/yarn.lock') }}
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd compiler install --frozen-lockfile
-      - name: Build plugin
-        working-directory: fixtures/eslint-v${{ matrix.eslint_major }}
-        run: node build.mjs
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Install fixture dependencies
         working-directory: ./fixtures/eslint-v${{ matrix.eslint_major }}
         run: yarn --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Build plugin
+        working-directory: fixtures/eslint-v${{ matrix.eslint_major }}
+        run: node build.mjs
       - name: Run lint test
         working-directory: ./fixtures/eslint-v${{ matrix.eslint_major }}
         run: yarn lint

.github/workflows/runtime_fuzz_tests.yml

@@ -8,6 +8,8 @@ on:
       - main
   workflow_dispatch:
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 

.github/workflows/runtime_prereleases.yml

@@ -13,21 +13,45 @@ on:
       dist_tag:
         required: true
         type: string
+      enableFailureNotification:
+        description: 'Whether to notify the team on Discord when the release fails. Useful if this workflow is called from an automation.'
+        required: false
+        type: boolean
+      only_packages:
+        description: Packages to publish (space separated)
+        type: string
+      skip_packages:
+        description: Packages to NOT publish (space separated)
+        type: string
+      dry:
+        required: true
+        description: Dry run instead of publish?
+        type: boolean
+        default: true
     secrets:
+      DISCORD_WEBHOOK_URL:
+        description: 'Discord webhook URL to notify on failure. Only required if enableFailureNotification is true.'
+        required: false
+      GH_TOKEN:
+        required: true
       NPM_TOKEN:
         required: true
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
   SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
-  GH_TOKEN: ${{ github.token }}
   NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
 
 jobs:
   publish_prerelease:
     name: Publish prelease (${{ inputs.release_channel }}) ${{ inputs.commit_sha }} @${{ inputs.dist_tag }}
     runs-on: ubuntu-latest
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
@@ -45,8 +69,44 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: cp ./scripts/release/ci-npmrc ~/.npmrc
       - run: |
-          scripts/release/prepare-release-from-ci.js --skipTests -r ${{ inputs.release_channel }} --commit=${{ inputs.commit_sha }}
-          cp ./scripts/release/ci-npmrc ~/.npmrc
-          scripts/release/publish.js --ci --tags ${{ inputs.dist_tag }}
+          GH_TOKEN=${{ secrets.GH_TOKEN }} scripts/release/prepare-release-from-ci.js --skipTests -r ${{ inputs.release_channel }} --commit=${{ inputs.commit_sha }}
+      - name: Check prepared files
+        run: ls -R build/node_modules
+      - if: '${{ inputs.only_packages }}'
+        name: 'Publish ${{ inputs.only_packages }}'
+        run: |
+          scripts/release/publish.js \
+            --ci \
+            --skipTests \
+            --tags=${{ inputs.dist_tag }} \
+            --onlyPackages=${{ inputs.only_packages }} ${{ (inputs.dry && '') || '\'}}
+            ${{ inputs.dry && '--dry'}}
+      - if: '${{ inputs.skip_packages }}'
+        name: 'Publish all packages EXCEPT ${{ inputs.skip_packages }}'
+        run: |
+          scripts/release/publish.js \
+            --ci \
+            --skipTests \
+            --tags=${{ inputs.dist_tag }} \
+            --skipPackages=${{ inputs.skip_packages }} ${{ (inputs.dry && '') || '\'}}
+            ${{ inputs.dry && '--dry'}}
+      - if: '${{ !(inputs.skip_packages && inputs.only_packages) }}'
+        name: 'Publish all packages'
+        run: |
+          scripts/release/publish.js \
+            --ci \
+            --tags=${{ inputs.dist_tag }} ${{ (inputs.dry && '') || '\'}}
+            ${{ inputs.dry && '--dry'}}
+      - name: Notify Discord on failure
+        if: failure() && inputs.enableFailureNotification == true
+        uses: tsickert/discord-webhook@86dc739f3f165f16dadc5666051c367efa1692f4
+        with:
+          webhook-url: ${{ secrets.DISCORD_WEBHOOK_URL }}
+          embed-author-name: "GitHub Actions"
+          embed-title: 'Publish of $${{ inputs.release_channel }} release failed'
+          embed-url: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}/attempts/${{ github.run_attempt }}

.github/workflows/runtime_prereleases_manual.yml

@@ -5,15 +5,57 @@ on:
     inputs:
       prerelease_commit_sha:
         required: true
+      only_packages:
+        description: Packages to publish (space separated)
+        type: string
+      skip_packages:
+        description: Packages to NOT publish (space separated)
+        type: string
+      dry:
+        required: true
+        description: Dry run instead of publish?
+        type: boolean
+        default: true
+      experimental_only:
+        type: boolean
+        description: Only publish to the experimental tag
+        default: false
+      force_notify:
+        description: Force a Discord notification?
+        type: boolean
+        default: false
+
+permissions: {}
 
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 
 jobs:
+  notify:
+    if: ${{ inputs.force_notify || inputs.dry == false || inputs.dry == 'false' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Discord Webhook Action
+        uses: tsickert/discord-webhook@86dc739f3f165f16dadc5666051c367efa1692f4
+        with:
+          webhook-url: ${{ secrets.DISCORD_WEBHOOK_URL }}
+          embed-author-name: ${{ github.event.sender.login }}
+          embed-author-url: ${{ github.event.sender.html_url }}
+          embed-author-icon-url: ${{ github.event.sender.avatar_url }}
+          embed-title: "⚠️ Publishing ${{ inputs.experimental_only && 'EXPERIMENTAL' || 'CANARY & EXPERIMENTAL' }} release ${{ (inputs.dry && ' (dry run)') || '' }}"
+          embed-description: |
+            ```json
+            ${{ toJson(inputs) }}
+            ```
+          embed-url: https://github.com/facebook/react/actions/runs/${{ github.run_id }}
 
   publish_prerelease_canary:
+    if: ${{ !inputs.experimental_only }}
     name: Publish to Canary channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     with:
       commit_sha: ${{ inputs.prerelease_commit_sha }}
       release_channel: stable
@@ -28,20 +70,33 @@ jobs:
       # downstream consumers might still expect that tag. We can remove this
       # after some time has elapsed and the change has been communicated.
       dist_tag: canary,next
+      only_packages: ${{ inputs.only_packages }}
+      skip_packages: ${{ inputs.skip_packages }}
+      dry: ${{ inputs.dry }}
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   publish_prerelease_experimental:
     name: Publish to Experimental channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     # NOTE: Intentionally running these jobs sequentially because npm
     # will sometimes fail if you try to concurrently publish two
     # different versions of the same package, even if they use different
     # dist tags.
     needs: publish_prerelease_canary
+    # Ensures the job runs even if canary is skipped
+    if: always()
     with:
       commit_sha: ${{ inputs.prerelease_commit_sha }}
       release_channel: experimental
       dist_tag: experimental
+      only_packages: ${{ inputs.only_packages }}
+      skip_packages: ${{ inputs.skip_packages }}
+      dry: ${{ inputs.dry }}
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/runtime_prereleases_nightly.yml

@@ -5,6 +5,8 @@ on:
     # At 10 minutes past 16:00 on Mon, Tue, Wed, Thu, and Fri
     - cron: 10 16 * * 1,2,3,4,5
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 
@@ -12,16 +14,26 @@ jobs:
   publish_prerelease_canary:
     name: Publish to Canary channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     with:
       commit_sha: ${{ github.sha }}
       release_channel: stable
       dist_tag: canary,next
+      enableFailureNotification: true
+      dry: false
     secrets:
+      DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
   publish_prerelease_experimental:
     name: Publish to Experimental channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     # NOTE: Intentionally running these jobs sequentially because npm
     # will sometimes fail if you try to concurrently publish two
     # different versions of the same package, even if they use different
@@ -31,5 +43,9 @@ jobs:
       commit_sha: ${{ github.sha }}
       release_channel: experimental
       dist_tag: experimental
+      enableFailureNotification: true
+      dry: false
     secrets:
+      DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/runtime_releases_from_npm_manual.yml

@@ -31,11 +31,12 @@ on:
         type: boolean
         default: false
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
   SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
-  GH_TOKEN: ${{ github.token }}
   NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
 
 jobs:
@@ -77,7 +78,9 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: cp ./scripts/release/ci-npmrc ~/.npmrc
       - if: '${{ inputs.only_packages }}'
         name: 'Prepare ${{ inputs.only_packages }} from NPM'

.github/workflows/shared_check_maintainer.yml

@@ -6,14 +6,12 @@ on:
       actor:
         required: true
         type: string
-      is_remote:
-        required: false
-        type: boolean
-        default: false
     outputs:
       is_core_team:
         value: ${{ jobs.check_maintainer.outputs.is_core_team }}
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
@@ -22,10 +20,12 @@ env:
 jobs:
   check_maintainer:
     runs-on: ubuntu-latest
+    permissions:
+      # We fetch the contents of the MAINTAINERS file
+      contents: read
     outputs:
       is_core_team: ${{ steps.check_if_actor_is_maintainer.outputs.result }}
     steps:
-      - uses: actions/checkout@v4
       - name: Check if actor is maintainer
         id: check_if_actor_is_maintainer
         uses: actions/github-script@v7
@@ -33,33 +33,20 @@ jobs:
           script: |
             const fs = require('fs');
             const actor = '${{ inputs.actor }}';
-            let isRemote = ${{ inputs.is_remote }};
-            if (typeof isRemote === 'string') {
-              isRemote = isRemote === 'true';
+            const res = await github.rest.repos.getContent({
+              owner: 'facebook',
+              repo: 'react',
+              path: 'MAINTAINERS',
+              ref: 'main',
+              headers: { Accept: 'application/vnd.github+json' }
+            });
+            if (res.status !== 200) {
+              console.error(res);
+              throw new Error('Unable to fetch MAINTAINERS file');
             }
-            if (typeof isRemote !== 'boolean') {
-              throw new Error(`Invalid \`isRemote\` input. Expected a boolean, got: ${isRemote}`);
-            }
-
-            let content = null;
-            if (isRemote === true) {
-              const res = await github.rest.repos.getContent({
-                owner: 'facebook',
-                repo: 'react',
-                path: 'MAINTAINERS',
-                ref: 'main',
-                headers: { Accept: 'application/vnd.github+json' }
-              });
-              if (res.status !== 200) {
-                console.error(res);
-                throw new Error('Unable to fetch MAINTAINERS file');
-              }
-              content = Buffer.from(res.data.content, 'base64').toString();
-            } else {
-              content = await fs.readFileSync('./MAINTAINERS', { encoding: 'utf8' });
-            }
-            if (content === null) {
-              throw new Error('Unable to retrieve local or http MAINTAINERS file');
+            content = Buffer.from(res.data.content, 'base64').toString();
+            if (content == null || typeof content !== 'string') {
+              throw new Error('Unable to retrieve MAINTAINERS file');
             }
 
             const maintainers = new Set(content.split('\n'));

.github/workflows/shared_cleanup_merged_branch_caches.yml

@@ -1,11 +1,17 @@
 # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#force-deletion-of-caches-overriding-default-cache-eviction-policy
 
-name: (Shared) Cleanup Branch Caches
+name: (Shared) Cleanup Merged Branch Caches
 on:
   pull_request:
     types:
       - closed
   workflow_dispatch:
+    inputs:
+      pr_number:
+        required: true
+        type: string
+
+permissions: {}
 
 jobs:
   cleanup:
@@ -23,13 +29,13 @@ jobs:
 
           ## Setting this to not fail the workflow while deleting cache keys.
           set +e
-          echo "Deleting caches..."
           for cacheKey in $cacheKeysForPR
           do
               gh cache delete $cacheKey
+              echo "Deleting $cacheKey"
           done
           echo "Done"
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           GH_REPO: ${{ github.repository }}
-          BRANCH: refs/pull/${{ github.event.pull_request.number }}/merge
+          BRANCH: refs/pull/${{ inputs.pr_number || github.event.pull_request.number }}/merge

.github/workflows/shared_cleanup_stale_branch_caches.yml

@@ -0,0 +1,36 @@
+# https://github.com/actions/cache/blob/main/tips-and-workarounds.md#force-deletion-of-caches-overriding-default-cache-eviction-policy
+
+name: (Shared) Cleanup Stale Branch Caches
+on:
+  schedule:
+    # Every 6 hours
+    - cron: 0 */6 * * *
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  cleanup:
+    runs-on: ubuntu-latest
+    permissions:
+      # `actions:write` permission is required to delete caches
+      #   See also: https://docs.github.com/en/rest/actions/cache?apiVersion=2022-11-28#delete-a-github-actions-cache-for-a-repository-using-a-cache-id
+      actions: write
+      contents: read
+    steps:
+      - name: Cleanup
+        run: |
+          echo "Fetching list of cache keys"
+          cacheKeysForPR=$(gh cache list --limit 100 --json id,ref --jq '.[] | select(.ref != "refs/heads/main") | .id')
+
+          ## Setting this to not fail the workflow while deleting cache keys.
+          set +e
+          for cacheKey in $cacheKeysForPR
+          do
+              gh cache delete $cacheKey
+              echo "Deleting $cacheKey"
+          done
+          echo "Done"
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_REPO: ${{ github.repository }}

.github/workflows/shared_close_direct_sync_branch_prs.yml

@@ -5,6 +5,8 @@ on:
     branches:
       - 'builds/facebook-**'
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
   # https://github.com/actions/cache/blob/main/tips-and-workarounds.md#cache-segment-restore-timeout
@@ -13,6 +15,9 @@ env:
 jobs:
   close_pr:
     runs-on: ubuntu-latest
+    permissions:
+      # Used to create a review and close PRs
+      pull-requests: write
     steps:
       - name: Close PR
         uses: actions/github-script@v7

.github/workflows/shared_label_core_team_prs.yml

@@ -2,6 +2,9 @@ name: (Shared) Label Core Team PRs
 
 on:
   pull_request_target:
+    types: [opened]
+
+permissions: {}
 
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
@@ -9,8 +12,24 @@ env:
   SEGMENT_DOWNLOAD_TIMEOUT_MINS: 1
 
 jobs:
+  check_access:
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - run: echo ${{ github.event.pull_request.author_association }}
+      - name: Check is member or collaborator
+        id: check_is_member_or_collaborator
+        if: ${{ github.event.pull_request.author_association == 'MEMBER' || github.event.pull_request.author_association == 'COLLABORATOR' }}
+        run: echo "is_member_or_collaborator=true" >> "$GITHUB_OUTPUT"
+
   check_maintainer:
+    if: ${{ needs.check_access.outputs.is_member_or_collaborator == 'true' || needs.check_access.outputs.is_member_or_collaborator == true }}
+    needs: [check_access]
     uses: facebook/react/.github/workflows/shared_check_maintainer.yml@main
+    permissions:
+      # Used by check_maintainer
+      contents: read
     with:
       actor: ${{ github.event.pull_request.user.login }}
 
@@ -18,6 +37,11 @@ jobs:
     if: ${{ needs.check_maintainer.outputs.is_core_team == 'true' }}
     runs-on: ubuntu-latest
     needs: check_maintainer
+    permissions:
+      # Used to add labels on issues
+      issues: write
+      # Used to add labels on PRs
+      pull-requests: write
     steps:
       - name: Label PR as React Core Team
         uses: actions/github-script@v7

.github/workflows/shared_lint.yml

@@ -5,6 +5,8 @@ on:
     branches: [main]
   pull_request:
 
+permissions: {}
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}-${{ github.event.pull_request.number || github.run_id }}
   cancel-in-progress: true
@@ -27,6 +29,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -34,6 +37,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn prettier-check
 
   eslint:
@@ -48,6 +52,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -55,6 +60,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: node ./scripts/tasks/eslint
 
   check_license:
@@ -69,6 +75,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -76,6 +83,7 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: ./scripts/ci/check_license.sh
 
   test_print_warnings:
@@ -90,6 +98,7 @@ jobs:
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
         uses: actions/cache@v4
+        id: node_modules
         with:
           path: |
             **/node_modules
@@ -97,4 +106,5 @@ jobs:
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
       - run: ./scripts/ci/test_print_warnings.sh

.github/workflows/shared_stale.yml

@@ -6,6 +6,11 @@ on:
     - cron: '0 * * * *'
   workflow_dispatch:
 
+permissions:
+  # https://github.com/actions/stale/tree/v9/?tab=readme-ov-file#recommended-permissions
+  issues: write
+  pull-requests: write
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 

.nvmrc

@@ -1 +1 @@
-v18.20.1
+v20.19.0

.prettierrc.js

@@ -3,13 +3,12 @@
 const {esNextPaths} = require('./scripts/shared/pathsByLanguageVersion');
 
 module.exports = {
-  plugins: ['prettier-plugin-hermes-parser'],
   bracketSpacing: false,
   singleQuote: true,
   bracketSameLine: true,
   trailingComma: 'es5',
   printWidth: 80,
-  parser: 'hermes',
+  parser: 'flow',
   arrowParens: 'avoid',
   overrides: [
     {

CHANGELOG-canary.md

@@ -1,18 +0,0 @@
-## March 22, 2024 (18.3.0-canary-670811593-20240322)
-
-## React
-- Added `useActionState` to replace `useFormState` and added `pending` value ([#28491](https://github.com/facebook/react/pull/28491)).
-
-## October 5, 2023 (18.3.0-canary-546178f91-20231005)
-
-### React
-
-- Added support for async functions to be passed to `startTransition`. 
-- `useTransition` now triggers the nearest error boundary instead of a global error.
-- Added `useOptimistic`, a new Hook for handling optimistic UI updates. It optimistically updates the UI before receiving confirmation from a server or external source.
-
-### React DOM
-
-- Added support for passing async functions to the `action` prop on `<form>`. When the function passed to `action` is marked with [`'use server'`](https://react.dev/reference/react/use-server), the form is [progressively enhanced](https://developer.mozilla.org/en-US/docs/Glossary/Progressive_Enhancement).
-- Added `useFormStatus`, a new Hook for checking the submission state of a form.
-- Added `useFormState`, a new Hook for updating state upon form submission. When the function passed to `useFormState` is marked with [`'use server'`](https://react.dev/reference/react/use-server), the update is [progressively enhanced](https://developer.mozilla.org/en-US/docs/Glossary/Progressive_Enhancement).

CHANGELOG.md

@@ -1,3 +1,50 @@
+## 19.1.0 (March 28, 2025)
+
+### Owner Stack
+
+An Owner Stack is a string representing the components that are directly responsible for rendering a particular component. You can log Owner Stacks when debugging or use Owner Stacks to enhance error overlays or other development tools. Owner Stacks are only available in development builds. Component Stacks in production are unchanged.
+
+* An Owner Stack is a development-only stack trace that helps identify which components are responsible for rendering a particular component. An Owner Stack is distinct from a Component Stacks, which shows the hierarchy of components leading to an error.
+* The [captureOwnerStack API](https://react.dev/reference/react/captureOwnerStack) is only available in development mode and returns a Owner Stack, if available. The API can be used to enhance error overlays or log component relationships when debugging. [#29923](https://github.com/facebook/react/pull/29923), [#32353](https://github.com/facebook/react/pull/32353), [#30306](https://github.com/facebook/react/pull/30306),
+[#32538](https://github.com/facebook/react/pull/32538), [#32529](https://github.com/facebook/react/pull/32529), [#32538](https://github.com/facebook/react/pull/32538)
+
+### React
+* Enhanced support for Suspense boundaries to be used anywhere, including the client, server, and during hydration. [#32069](https://github.com/facebook/react/pull/32069), [#32163](https://github.com/facebook/react/pull/32163), [#32224](https://github.com/facebook/react/pull/32224), [#32252](https://github.com/facebook/react/pull/32252)
+* Reduced unnecessary client rendering through improved hydration scheduling [#31751](https://github.com/facebook/react/pull/31751)
+* Increased priority of client rendered Suspense boundaries [#31776](https://github.com/facebook/react/pull/31776)
+* Fixed frozen fallback states by rendering unfinished Suspense boundaries on the client. [#31620](https://github.com/facebook/react/pull/31620)
+* Reduced garbage collection pressure by improving Suspense boundary retries. [#31667](https://github.com/facebook/react/pull/31667)
+* Fixed erroneous “Waiting for Paint” log when the passive effect phase was not delayed [#31526](https://github.com/facebook/react/pull/31526)
+* Fixed a regression causing key warnings for flattened positional children in development mode. [#32117](https://github.com/facebook/react/pull/32117)
+* Updated `useId` to use valid CSS selectors, changing format from `:r123:` to `«r123»`. [#32001](https://github.com/facebook/react/pull/32001)
+* Added a dev-only warning for null/undefined created in useEffect, useInsertionEffect, and useLayoutEffect. [#32355](https://github.com/facebook/react/pull/32355)
+* Fixed a bug where dev-only methods were exported in production builds. React.act is no longer available in production builds. [#32200](https://github.com/facebook/react/pull/32200)
+* Improved consistency across prod and dev to improve compatibility with Google Closure Complier and bindings [#31808](https://github.com/facebook/react/pull/31808)
+* Improve passive effect scheduling for consistent task yielding. [#31785](https://github.com/facebook/react/pull/31785)
+* Fixed asserts in React Native when passChildrenWhenCloningPersistedNodes is enabled for OffscreenComponent rendering. [#32528](https://github.com/facebook/react/pull/32528)
+* Fixed component name resolution for Portal [#32640](https://github.com/facebook/react/pull/32640)
+* Added support for beforetoggle and toggle events on the dialog element. #32479 [#32479](https://github.com/facebook/react/pull/32479)
+
+### React DOM
+* Fixed double warning when the `href` attribute is an empty string [#31783](https://github.com/facebook/react/pull/31783)
+ * Fixed an edge case where `getHoistableRoot()` didn’t work properly when the container was a Document [#32321](https://github.com/facebook/react/pull/32321)
+* Removed support for using HTML comments (e.g. `<!-- -->`) as a DOM container. [#32250](https://github.com/facebook/react/pull/32250)
+* Added support for `<script>` and `<template>` tags to be nested within `<select>` tags. [#31837](https://github.com/facebook/react/pull/31837)
+* Fixed responsive images to be preloaded as HTML instead of headers [#32445](https://github.com/facebook/react/pull/32445)
+
+### use-sync-external-store
+* Added `exports` field to `package.json` for `use-sync-external-store` to support various entrypoints. [#25231](https://github.com/facebook/react/pull/25231)
+
+### React Server Components
+* Added `unstable_prerender`, a new experimental API for prerendering React Server Components on the server [#31724](https://github.com/facebook/react/pull/31724)
+* Fixed an issue where streams would hang when receiving new chunks after a global error [#31840](https://github.com/facebook/react/pull/31840), [#31851](https://github.com/facebook/react/pull/31851)
+* Fixed an issue where pending chunks were counted twice. [#31833](https://github.com/facebook/react/pull/31833)
+* Added support for streaming in edge environments [#31852](https://github.com/facebook/react/pull/31852)
+* Added support for sending custom error names from a server so that they are available in the client for console replaying. [#32116](https://github.com/facebook/react/pull/32116)
+* Updated the server component wire format to remove IDs for hints and console.log because they have no return value [#31671](https://github.com/facebook/react/pull/31671)
+* Exposed `registerServerReference` in client builds to handle server references in different environments. [#32534](https://github.com/facebook/react/pull/32534)
+* Added react-server-dom-parcel package which integrates Server Components with the [Parcel bundler](https://parceljs.org/) [#31725](https://github.com/facebook/react/pull/31725), [#32132](https://github.com/facebook/react/pull/32132), [#31799](https://github.com/facebook/react/pull/31799), [#32294](https://github.com/facebook/react/pull/32294), [#31741](https://github.com/facebook/react/pull/31741)
+
 ## 19.0.0 (December 5, 2024)
 
 Below is a list of all new features, APIs, deprecations, and breaking changes. Read [React 19 release post](https://react.dev/blog/2024/04/25/react-19) and [React 19 upgrade guide](https://react.dev/blog/2024/04/25/react-19-upgrade-guide) for more information.

ReactVersions.js

@@ -18,7 +18,7 @@
 //
 //   0.0.0-experimental-241c4467e-20200129
 
-const ReactVersion = '19.1.0';
+const ReactVersion = '19.2.0';
 
 // The label used by the @canary channel. Represents the upcoming release's
 // stability. Most of the time, this will be "canary", but we may temporarily
@@ -33,7 +33,7 @@ const canaryChannelLabel = 'canary';
 const rcNumber = 0;
 
 const stablePackages = {
-  'eslint-plugin-react-hooks': '5.2.0',
+  'eslint-plugin-react-hooks': '6.1.0',
   'jest-react': '0.17.0',
   react: ReactVersion,
   'react-art': ReactVersion,
@@ -42,12 +42,12 @@ const stablePackages = {
   'react-server-dom-turbopack': ReactVersion,
   'react-server-dom-parcel': ReactVersion,
   'react-is': ReactVersion,
-  'react-reconciler': '0.32.0',
-  'react-refresh': '0.17.0',
+  'react-reconciler': '0.33.0',
+  'react-refresh': '0.18.0',
   'react-test-renderer': ReactVersion,
-  'use-subscription': '1.11.0',
-  'use-sync-external-store': '1.5.0',
-  scheduler: '0.26.0',
+  'use-subscription': '1.12.0',
+  'use-sync-external-store': '1.6.0',
+  scheduler: '0.27.0',
 };
 
 // These packages do not exist in the @canary or @latest channel, only

compiler/.gitignore

@@ -1,28 +1,14 @@
 .DS_Store
 .spr.yml
 
-# Generated by Cargo
-# will have compiled files and executables
-debug/
-target/
-
-# These are backup files generated by rustfmt
-**/*.rs.bk
-
-# MSVC Windows builds of rustc generate these, which store debugging information
-*.pdb
-
 node_modules
 .watchmanconfig
 .watchman-cookie-*
 dist
 .vscode
 !packages/playground/.vscode
-.spr.yml
 testfilter.txt
 
-bundle-oss.sh
-
 # forgive
 *.vsix
 .vscode-test

compiler/CHANGELOG.md

@@ -0,0 +1,65 @@
+## 19.1.0-rc.2 (May 14, 2025)
+
+## babel-plugin-react-compiler
+
+* Fix for string attribute values with emoji [#33096](https://github.com/facebook/react/pull/33096) by [@josephsavona](https://github.com/josephsavona)
+
+## 19.1.0-rc.1 (April 21, 2025)
+
+## eslint-plugin-react-hooks
+* Temporarily disable ref access in render validation [#32839](https://github.com/facebook/react/pull/32839) by [@poteto](https://github.com/poteto)
+* Fix type error with recommended config [#32666](https://github.com/facebook/react/pull/32666) by [@niklasholm](https://github.com/niklasholm)
+* Merge rule from eslint-plugin-react-compiler into `react-hooks` plugin [#32416](https://github.com/facebook/react/pull/32416) by [@michaelfaith](https://github.com/michaelfaith)
+* Add dev dependencies for typescript migration [#32279](https://github.com/facebook/react/pull/32279) by [@michaelfaith](https://github.com/michaelfaith)
+* Support v9 context api [#32045](https://github.com/facebook/react/pull/32045) by [@michaelfaith](https://github.com/michaelfaith)
+* Support eslint 8+ flat plugin syntax out of the box for eslint-plugin-react-compiler [#32120](https://github.com/facebook/react/pull/32120) by [@orta](https://github.com/orta)
+
+## babel-plugin-react-compiler
+* Support satisfies operator [#32742](https://github.com/facebook/react/pull/32742) by [@rodrigofariow](https://github.com/rodrigofariow)
+* Fix inferEffectDependencies lint false positives [#32769](https://github.com/facebook/react/pull/32769) by [@mofeiZ](https://github.com/mofeiZ)
+* Fix hoisting of let declarations [#32724](https://github.com/facebook/react/pull/32724) by [@mofeiZ](https://github.com/mofeiZ)
+* Avoid failing builds when import specifiers conflict or shadow vars [#32663](https://github.com/facebook/react/pull/32663) by [@mofeiZ](https://github.com/mofeiZ)
+* Optimize components declared with arrow function and implicit return and `compilationMode: 'infer'` [#31792](https://github.com/facebook/react/pull/31792) by [@dimaMachina](https://github.com/dimaMachina)
+* Validate static components [#32683](https://github.com/facebook/react/pull/32683) by [@josephsavona](https://github.com/josephsavona)
+* Hoist dependencies from functions more conservatively [#32616](https://github.com/facebook/react/pull/32616) by [@mofeiZ](https://github.com/mofeiZ)
+* Implement NumericLiteral as ObjectPropertyKey [#31791](https://github.com/facebook/react/pull/31791) by [@dimaMachina](https://github.com/dimaMachina)
+* Avoid bailouts when inserting gating [#32598](https://github.com/facebook/react/pull/32598) by [@mofeiZ](https://github.com/mofeiZ)
+* Stop bailing out early for hoisted gated functions [#32597](https://github.com/facebook/react/pull/32597) by [@mofeiZ](https://github.com/mofeiZ)
+* Add shape for Array.from [#32522](https://github.com/facebook/react/pull/32522) by [@mofeiZ](https://github.com/mofeiZ)
+* Patch array and argument spread mutability [#32521](https://github.com/facebook/react/pull/32521) by [@mofeiZ](https://github.com/mofeiZ)
+* Make CompilerError compatible with reflection [#32539](https://github.com/facebook/react/pull/32539) by [@poteto](https://github.com/poteto)
+* Add simple walltime measurement [#32331](https://github.com/facebook/react/pull/32331) by [@poteto](https://github.com/poteto)
+* Improve error messages for unhandled terminal and instruction kinds [#32324](https://github.com/facebook/react/pull/32324) by [@inottn](https://github.com/inottn)
+* Handle TSInstantiationExpression in lowerExpression [#32302](https://github.com/facebook/react/pull/32302) by [@inottn](https://github.com/inottn)
+* Fix invalid Array.map type [#32095](https://github.com/facebook/react/pull/32095) by [@mofeiZ](https://github.com/mofeiZ)
+* Patch for JSX escape sequences in @babel/generator [#32131](https://github.com/facebook/react/pull/32131) by [@mofeiZ](https://github.com/mofeiZ)
+* `JSXText` emits incorrect with bracket [#32138](https://github.com/facebook/react/pull/32138) by [@himself65](https://github.com/himself65)
+* Validation against calling impure functions [#31960](https://github.com/facebook/react/pull/31960) by [@josephsavona](https://github.com/josephsavona)
+* Always target node [#32091](https://github.com/facebook/react/pull/32091) by [@poteto](https://github.com/poteto)
+* Patch compilationMode:infer object method edge case [#32055](https://github.com/facebook/react/pull/32055) by [@mofeiZ](https://github.com/mofeiZ)
+* Generate ts defs [#31994](https://github.com/facebook/react/pull/31994) by [@poteto](https://github.com/poteto)
+* Relax react peer dep requirement [#31915](https://github.com/facebook/react/pull/31915) by [@poteto](https://github.com/poteto)
+* Allow type cast expressions with refs [#31871](https://github.com/facebook/react/pull/31871) by [@josephsavona](https://github.com/josephsavona)
+* Add shape for global Object.keys [#31583](https://github.com/facebook/react/pull/31583) by [@mofeiZ](https://github.com/mofeiZ)
+* Optimize method calls w props receiver [#31775](https://github.com/facebook/react/pull/31775) by [@josephsavona](https://github.com/josephsavona)
+* Fix dropped ref with spread props in InlineJsxTransform [#31726](https://github.com/facebook/react/pull/31726) by [@jackpope](https://github.com/jackpope)
+* Support for non-declatation for in/of iterators [#31710](https://github.com/facebook/react/pull/31710) by [@mvitousek](https://github.com/mvitousek)
+* Support for context variable loop iterators [#31709](https://github.com/facebook/react/pull/31709) by [@mvitousek](https://github.com/mvitousek)
+* Replace deprecated dependency in `eslint-plugin-react-compiler` [#31629](https://github.com/facebook/react/pull/31629) by [@rakleed](https://github.com/rakleed)
+* Support enableRefAsProp in jsx transform [#31558](https://github.com/facebook/react/pull/31558) by [@jackpope](https://github.com/jackpope)
+* Fix: ref.current now correctly reactive [#31521](https://github.com/facebook/react/pull/31521) by [@mofeiZ](https://github.com/mofeiZ)
+* Outline JSX with non-jsx children [#31442](https://github.com/facebook/react/pull/31442) by [@gsathya](https://github.com/gsathya)
+* Outline jsx with duplicate attributes [#31441](https://github.com/facebook/react/pull/31441) by [@gsathya](https://github.com/gsathya)
+* Store original and new prop names [#31440](https://github.com/facebook/react/pull/31440) by [@gsathya](https://github.com/gsathya)
+* Stabilize compiler output: sort deps and decls by name [#31362](https://github.com/facebook/react/pull/31362) by [@mofeiZ](https://github.com/mofeiZ)
+* Bugfix for hoistable deps for nested functions [#31345](https://github.com/facebook/react/pull/31345) by [@mofeiZ](https://github.com/mofeiZ)
+* Remove compiler runtime-compat fixture library [#31430](https://github.com/facebook/react/pull/31430) by [@poteto](https://github.com/poteto)
+* Wrap inline jsx transform codegen in conditional [#31267](https://github.com/facebook/react/pull/31267) by [@jackpope](https://github.com/jackpope)
+* Check if local identifier is a hook when resolving globals [#31384](https://github.com/facebook/react/pull/31384) by [@poteto](https://github.com/poteto)
+* Handle member expr as computed property [#31344](https://github.com/facebook/react/pull/31344) by [@gsathya](https://github.com/gsathya)
+* Fix to ref access check to ban ref?.current [#31360](https://github.com/facebook/react/pull/31360) by [@mvitousek](https://github.com/mvitousek)
+* InlineJSXTransform transforms jsx inside function expressions [#31282](https://github.com/facebook/react/pull/31282) by [@josephsavona](https://github.com/josephsavona)
+
+## Other
+* Add shebang to banner [#32225](https://github.com/facebook/react/pull/32225) by [@Jeremy-Hibiki](https://github.com/Jeremy-Hibiki)
+* remove terser from react-compiler-runtime build [#31326](https://github.com/facebook/react/pull/31326) by [@henryqdineen](https://github.com/henryqdineen)

compiler/apps/playground/__tests__/e2e/__snapshots__/page.spec.ts/compilationMode-all-output.txt

@@ -1,5 +1,5 @@
 import { c as _c } from "react/compiler-runtime"; // 
-        @compilationMode(all)
+        @compilationMode:"all"
 function nonReactFn() {
   const $ = _c(1);
   let t0;

compiler/apps/playground/__tests__/e2e/__snapshots__/page.spec.ts/compilationMode-infer-output.txt

@@ -1,4 +1,4 @@
-// @compilationMode(infer)
+// @compilationMode:"infer"
 function nonReactFn() {
   return {};
 }

compiler/apps/playground/__tests__/e2e/page.spec.ts

@@ -92,7 +92,7 @@ function useFoo(propVal: {+baz: number}) {
   },
   {
     name: 'compilationMode-infer',
-    input: `// @compilationMode(infer)
+    input: `// @compilationMode:"infer"
 function nonReactFn() {
   return {};
 }
@@ -101,7 +101,7 @@ function nonReactFn() {
   },
   {
     name: 'compilationMode-all',
-    input: `// @compilationMode(all)
+    input: `// @compilationMode:"all"
 function nonReactFn() {
   return {};
 }

compiler/apps/playground/components/Editor/EditorImpl.tsx

@@ -19,7 +19,9 @@ import BabelPluginReactCompiler, {
   PluginOptions,
   CompilerPipelineValue,
   parsePluginOptions,
-} from 'babel-plugin-react-compiler/src';
+  printReactiveFunctionWithOutlined,
+  printFunctionWithOutlined,
+} from 'babel-plugin-react-compiler';
 import clsx from 'clsx';
 import invariant from 'invariant';
 import {useSnackbar} from 'notistack';
@@ -41,8 +43,6 @@ import {
   default as Output,
   PrintedCompilerPipelineValue,
 } from './Output';
-import {printFunctionWithOutlined} from 'babel-plugin-react-compiler/src/HIR/PrintHIR';
-import {printReactiveFunctionWithOutlined} from 'babel-plugin-react-compiler/src/ReactiveScopes/PrintReactiveFunction';
 import {transformFromAstSync} from '@babel/core';
 
 function parseInput(

compiler/apps/playground/components/Editor/Input.tsx

@@ -6,7 +6,7 @@
  */
 
 import MonacoEditor, {loader, type Monaco} from '@monaco-editor/react';
-import {CompilerErrorDetail} from 'babel-plugin-react-compiler/src';
+import {CompilerErrorDetail} from 'babel-plugin-react-compiler';
 import invariant from 'invariant';
 import type {editor} from 'monaco-editor';
 import * as monaco from 'monaco-editor';

compiler/apps/playground/components/Editor/Output.tsx

@@ -11,7 +11,7 @@ import {
   InformationCircleIcon,
 } from '@heroicons/react/outline';
 import MonacoEditor, {DiffEditor} from '@monaco-editor/react';
-import {type CompilerError} from 'babel-plugin-react-compiler/src';
+import {type CompilerError} from 'babel-plugin-react-compiler';
 import parserBabel from 'prettier/plugins/babel';
 import * as prettierPluginEstree from 'prettier/plugins/estree';
 import * as prettier from 'prettier/standalone';

compiler/apps/playground/lib/reactCompilerMonacoDiagnostics.ts

@@ -6,10 +6,7 @@
  */
 
 import {Monaco} from '@monaco-editor/react';
-import {
-  CompilerErrorDetail,
-  ErrorSeverity,
-} from 'babel-plugin-react-compiler/src';
+import {CompilerErrorDetail, ErrorSeverity} from 'babel-plugin-react-compiler';
 import {MarkerSeverity, type editor} from 'monaco-editor';
 
 function mapReactCompilerSeverityToMonaco(
@@ -54,7 +51,7 @@ export function renderReactCompilerMarkers({
   model,
   details,
 }: ReactCompilerMarkerConfig): void {
-  let markers = [];
+  const markers: Array<editor.IMarkerData> = [];
   for (const detail of details) {
     const marker = mapReactCompilerDiagnosticToMonacoMarker(detail, monaco);
     if (marker == null) {

compiler/apps/playground/package.json

@@ -4,7 +4,7 @@
   "private": true,
   "scripts": {
     "dev": "cd ../.. && concurrently --kill-others -n compiler,runtime,playground \"yarn workspace babel-plugin-react-compiler run watch\" \"yarn workspace react-compiler-runtime run watch\" \"wait-on packages/babel-plugin-react-compiler/dist/index.js && cd apps/playground && NODE_ENV=development next dev\"",
-    "build:compiler": "cd ../.. && concurrently -n compiler,runtime \"yarn workspace babel-plugin-react-compiler run build\" \"yarn workspace react-compiler-runtime run build\"",
+    "build:compiler": "cd ../.. && concurrently -n compiler,runtime \"yarn workspace babel-plugin-react-compiler run build --dts\" \"yarn workspace react-compiler-runtime run build\"",
     "build": "yarn build:compiler && next build",
     "postbuild": "node ./scripts/downloadFonts.js",
     "preinstall": "cd ../.. && yarn install --frozen-lockfile",
@@ -27,7 +27,7 @@
     "@babel/types": "7.26.3",
     "@heroicons/react": "^1.0.6",
     "@monaco-editor/react": "^4.4.6",
-    "@playwright/test": "^1.42.1",
+    "@playwright/test": "^1.51.1",
     "@use-gesture/react": "^10.2.22",
     "hermes-eslint": "^0.25.0",
     "hermes-parser": "^0.25.0",

compiler/apps/playground/scripts/link-compiler.sh

@@ -8,8 +8,8 @@ set -eo pipefail
 
 HERE=$(pwd)
 
-cd ../../packages/react-compiler-runtime && yarn --silent link && cd $HERE
-cd ../../packages/babel-plugin-react-compiler && yarn --silent link && cd $HERE
+cd ../../packages/react-compiler-runtime && yarn --silent link && cd "$HERE"
+cd ../../packages/babel-plugin-react-compiler && yarn --silent link && cd "$HERE"
 
 yarn --silent link babel-plugin-react-compiler
 yarn --silent link react-compiler-runtime

compiler/apps/playground/yarn.lock

@@ -781,12 +781,12 @@
   resolved "https://registry.yarnpkg.com/@pkgjs/parseargs/-/parseargs-0.11.0.tgz#a77ea742fab25775145434eb1d2328cf5013ac33"
   integrity sha512-+1VkjdD0QBLPodGrJUeqarH8VAIvQODIbwh9XpP5Syisf7YoQgsJKPNFoqqLQlu+VQ/tVSshMR6loPMn8U+dPg==
 
-"@playwright/test@^1.42.1":
-  version "1.47.2"
-  resolved "https://registry.yarnpkg.com/@playwright/test/-/test-1.47.2.tgz#dbe7051336bfc5cc599954214f9111181dbc7475"
-  integrity sha512-jTXRsoSPONAs8Za9QEQdyjFn+0ZQFjCiIztAIF6bi1HqhBzG9Ma7g1WotyiGqFSBRZjIEqMdT8RUlbk1QVhzCQ==
+"@playwright/test@^1.51.1":
+  version "1.51.1"
+  resolved "https://registry.yarnpkg.com/@playwright/test/-/test-1.51.1.tgz#75357d513221a7be0baad75f01e966baf9c41a2e"
+  integrity sha512-nM+kEaTSAoVlXmMPH10017vn3FSiFqr/bh4fKg9vmAdMfd9SDqRZNvPSiAHADc/itWak+qPvMPZQOPwCBW7k7Q==
   dependencies:
-    playwright "1.47.2"
+    playwright "1.51.1"
 
 "@rtsao/scc@^1.1.0":
   version "1.1.0"
@@ -1249,14 +1249,14 @@ camelcase-css@^2.0.1:
   integrity sha512-QOSvevhslijgYwRx6Rv7zKdMF8lbRmx+uQGx2+vDc+KI/eBnsy9kit5aj23AgGu3pa4t9AgwbnXWqS+iOY+2aA==
 
 caniuse-lite@^1.0.30001579:
-  version "1.0.30001669"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001669.tgz#fda8f1d29a8bfdc42de0c170d7f34a9cf19ed7a3"
-  integrity sha512-DlWzFDJqstqtIVx1zeSpIMLjunf5SmwOw0N2Ck/QSQdS8PLS4+9HrLaYei4w8BIAL7IB/UEDu889d8vhCTPA0w==
+  version "1.0.30001715"
+  resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001715.tgz"
+  integrity sha512-7ptkFGMm2OAOgvZpwgA4yjQ5SQbrNVGdRjzH0pBdy1Fasvcr+KAeECmbCAECzTuDuoX0FCY8KzUxjf9+9kfZEw==
 
 caniuse-lite@^1.0.30001646, caniuse-lite@^1.0.30001663:
-  version "1.0.30001664"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001664.tgz#d588d75c9682d3301956b05a3749652a80677df4"
-  integrity sha512-AmE7k4dXiNKQipgn7a2xg558IRqPN3jMQY/rOsbxDhrd0tyChwbITBfiwtnqz8bi2M5mIWbxAYBvk7W7QBUS2g==
+  version "1.0.30001715"
+  resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001715.tgz"
+  integrity sha512-7ptkFGMm2OAOgvZpwgA4yjQ5SQbrNVGdRjzH0pBdy1Fasvcr+KAeECmbCAECzTuDuoX0FCY8KzUxjf9+9kfZEw==
 
 chalk@^2.4.2:
   version "2.4.2"
@@ -3008,17 +3008,17 @@ pirates@^4.0.1:
   resolved "https://registry.yarnpkg.com/pirates/-/pirates-4.0.6.tgz#3018ae32ecfcff6c29ba2267cbf21166ac1f36b9"
   integrity sha512-saLsH7WeYYPiD25LDuLRRY/i+6HaPYr6G1OUlN39otzkSTxKnubR9RTxS3/Kk50s1g2JTgFwWQDQyplC5/SHZg==
 
-playwright-core@1.47.2:
-  version "1.47.2"
-  resolved "https://registry.yarnpkg.com/playwright-core/-/playwright-core-1.47.2.tgz#7858da9377fa32a08be46ba47d7523dbd9460a4e"
-  integrity sha512-3JvMfF+9LJfe16l7AbSmU555PaTl2tPyQsVInqm3id16pdDfvZ8TTZ/pyzmkbDrZTQefyzU7AIHlZqQnxpqHVQ==
+playwright-core@1.51.1:
+  version "1.51.1"
+  resolved "https://registry.yarnpkg.com/playwright-core/-/playwright-core-1.51.1.tgz#d57f0393e02416f32a47cf82b27533656a8acce1"
+  integrity sha512-/crRMj8+j/Nq5s8QcvegseuyeZPxpQCZb6HNk3Sos3BlZyAknRjoyJPFWkpNn8v0+P3WiwqFF8P+zQo4eqiNuw==
 
-playwright@1.47.2:
-  version "1.47.2"
-  resolved "https://registry.yarnpkg.com/playwright/-/playwright-1.47.2.tgz#155688aa06491ee21fb3e7555b748b525f86eb20"
-  integrity sha512-nx1cLMmQWqmA3UsnjaaokyoUpdVaaDhJhMoxX2qj3McpjnsqFHs516QAKYhqHAgOP+oCFTEOCOAaD1RgD/RQfA==
+playwright@1.51.1:
+  version "1.51.1"
+  resolved "https://registry.yarnpkg.com/playwright/-/playwright-1.51.1.tgz#ae1467ee318083968ad28d6990db59f47a55390f"
+  integrity sha512-kkx+MB2KQRkyxjYPc3a0wLZZoDczmppyGJIvQ43l+aZihkaVvmu/21kiyaHeHjiFxjxNNFnUncKmcGIyOojsaw==
   dependencies:
-    playwright-core "1.47.2"
+    playwright-core "1.51.1"
   optionalDependencies:
     fsevents "2.3.2"
 

compiler/package.json

@@ -37,7 +37,7 @@
     "prettier": "^3.3.3",
     "prettier-plugin-hermes-parser": "^0.26.0",
     "prompt-promise": "^1.0.3",
-    "rimraf": "^5.0.10",
+    "rimraf": "^6.0.1",
     "to-fast-properties": "^2.0.0",
     "tsup": "^8.4.0",
     "typescript": "^5.4.3",
@@ -45,7 +45,6 @@
     "yargs": "^17.7.2"
   },
   "resolutions": {
-    "rimraf": "5.0.10",
     "@babel/types": "7.26.3"
   },
   "packageManager": "yarn@1.22.22"

compiler/packages/babel-plugin-react-compiler/package.json

@@ -12,12 +12,12 @@
     "build": "rimraf dist && tsup",
     "test": "./scripts/link-react-compiler-runtime.sh && yarn snap:ci",
     "jest": "yarn build && ts-node node_modules/.bin/jest",
-    "snap": "node ../snap/dist/main.js",
+    "snap": "yarn workspace snap run snap",
     "snap:build": "yarn workspace snap run build",
     "snap:ci": "yarn snap:build && yarn snap",
     "ts:analyze-trace": "scripts/ts-analyze-trace.sh",
     "lint": "yarn eslint src",
-    "watch": "yarn build --watch"
+    "watch": "yarn build --dts --watch"
   },
   "dependencies": {
     "@babel/types": "^7.26.0"

compiler/packages/babel-plugin-react-compiler/scripts/jest/e2e-forget.config.js

@@ -7,7 +7,4 @@
 
 const makeE2EConfig = require('../jest/makeE2EConfig');
 
-const config = makeE2EConfig('e2e with forget', true);
-config.setupFilesAfterEnv = ['<rootDir>/../scripts/jest/setupEnvE2E.js'];
-
-module.exports = config;
+module.exports = makeE2EConfig('e2e with forget', true);

compiler/packages/babel-plugin-react-compiler/scripts/jest/makeTransform.ts

@@ -5,19 +5,16 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {jsx} from '@babel/plugin-syntax-jsx';
 import babelJest from 'babel-jest';
-import {compile} from 'babel-plugin-react-compiler';
+import {
+  validateEnvironmentConfig,
+  EnvironmentConfig,
+} from 'babel-plugin-react-compiler';
 import {execSync} from 'child_process';
 
 import type {NodePath, Visitor} from '@babel/traverse';
-import type {CallExpression, FunctionDeclaration} from '@babel/types';
-import * as t from '@babel/types';
-import {
-  EnvironmentConfig,
-  validateEnvironmentConfig,
-} from 'babel-plugin-react-compiler';
-import {basename} from 'path';
+import type {CallExpression} from '@babel/types';
+import BabelPluginReactCompiler from 'babel-plugin-react-compiler';
 
 /**
  * -- IMPORTANT --
@@ -28,10 +25,19 @@ import {basename} from 'path';
 const e2eTransformerCacheKey = 1;
 const forgetOptions: EnvironmentConfig = validateEnvironmentConfig({
   enableAssumeHooksFollowRulesOfReact: true,
-  enableFunctionOutlining: false,
 });
 const debugMode = process.env['DEBUG_FORGET_COMPILER'] != null;
 
+const compilerCacheKey = execSync(
+  'yarn --silent --cwd ../.. hash packages/babel-plugin-react-compiler/dist',
+)
+  .toString()
+  .trim();
+
+if (debugMode) {
+  console.log('cachebreaker', compilerCacheKey);
+}
+
 module.exports = (useForget: boolean) => {
   function createTransformer() {
     return babelJest.createTransformer({
@@ -42,15 +48,14 @@ module.exports = (useForget: boolean) => {
           plugins: [
             useForget
               ? [
-                  ReactForgetFunctionTransform,
+                  BabelPluginReactCompiler,
                   {
+                    environment: forgetOptions,
                     /*
                      * Jest hashes the babel config as a cache breaker.
                      * (see https://github.com/jestjs/jest/blob/v29.6.2/packages/babel-jest/src/index.ts#L84)
                      */
-                    compilerCacheKey: execSync(
-                      'yarn --silent --cwd ../.. hash packages/babel-plugin-react-compiler/dist',
-                    ).toString(),
+                    compilerCacheKey,
                     transformOptionsCacheKey: forgetOptions,
                     e2eTransformerCacheKey,
                   },
@@ -105,104 +110,3 @@ module.exports = (useForget: boolean) => {
     createTransformer,
   };
 };
-
-// Mostly copied from react/scripts/babel/transform-forget.js
-function isReactComponentLike(fn: NodePath<FunctionDeclaration>): boolean {
-  let isReactComponent = false;
-  let hasNoUseForgetDirective = false;
-
-  /*
-   * React components start with an upper case letter,
-   * React hooks start with `use`
-   */
-  if (
-    fn.node.id == null ||
-    (fn.node.id.name[0].toUpperCase() !== fn.node.id.name[0] &&
-      !/^use[A-Z0-9]/.test(fn.node.id.name))
-  ) {
-    return false;
-  }
-
-  fn.traverse({
-    DirectiveLiteral(path) {
-      if (path.node.value === 'use no forget') {
-        hasNoUseForgetDirective = true;
-      }
-    },
-
-    JSX(path) {
-      // Is there is a JSX node created in the current function context?
-      if (path.scope.getFunctionParent()?.path.node === fn.node) {
-        isReactComponent = true;
-      }
-    },
-
-    CallExpression(path) {
-      // Is there hook usage?
-      if (
-        path.node.callee.type === 'Identifier' &&
-        !/^use[A-Z0-9]/.test(path.node.callee.name)
-      ) {
-        isReactComponent = true;
-      }
-    },
-  });
-
-  if (hasNoUseForgetDirective) {
-    return false;
-  }
-
-  return isReactComponent;
-}
-
-function ReactForgetFunctionTransform() {
-  const compiledFns = new Set();
-  const visitor = {
-    FunctionDeclaration(fn: NodePath<FunctionDeclaration>, state: any): void {
-      if (compiledFns.has(fn.node)) {
-        return;
-      }
-
-      if (!isReactComponentLike(fn)) {
-        return;
-      }
-      if (debugMode) {
-        const filename = basename(state.file.opts.filename);
-        if (fn.node.loc && fn.node.id) {
-          console.log(
-            ` Compiling ${filename}:${fn.node.loc.start.line}:${fn.node.loc.start.column}  ${fn.node.id.name}`,
-          );
-        } else {
-          console.log(` Compiling ${filename} ${fn.node.id?.name}`);
-        }
-      }
-
-      const compiled = compile(
-        fn,
-        forgetOptions,
-        'Other',
-        'all_features',
-        '_c',
-        null,
-        null,
-        null,
-      );
-      compiledFns.add(compiled);
-
-      const fun = t.functionDeclaration(
-        compiled.id,
-        compiled.params,
-        compiled.body,
-        compiled.generator,
-        compiled.async,
-      );
-      fn.replaceWith(fun);
-      fn.skip();
-    },
-  };
-  return {
-    name: 'react-forget-e2e',
-    inherits: jsx,
-    visitor,
-  };
-}

compiler/packages/babel-plugin-react-compiler/scripts/jest/setupEnvE2E.js

@@ -1,16 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-const ReactCompilerRuntime = require('react/compiler-runtime');
-
-/*
- * Our e2e babel transform currently only compiles functions, not programs.
- * As a result, our e2e transpiled code does not contain an import for the
- * memo cache function. As a temporary hack, we add a `_c` global, which is
- * the name that is used for the import by default.
- */
-globalThis._c = ReactCompilerRuntime.c;

compiler/packages/babel-plugin-react-compiler/src/Babel/BabelPlugin.ts

@@ -73,7 +73,7 @@ export default function BabelPluginReactCompiler(
             pass.filename ?? null,
             opts.logger,
             opts.environment,
-            result?.retryErrors ?? [],
+            result,
           );
           if (ENABLE_REACT_COMPILER_TIMINGS === true) {
             performance.mark(`${filename}:end`, {

compiler/packages/babel-plugin-react-compiler/src/CompilerError.ts

@@ -6,6 +6,7 @@
  */
 
 import type {SourceLocation} from './HIR';
+import {Err, Ok, Result} from './Utils/Result';
 import {assertExhaustive} from './Utils/utils';
 
 export enum ErrorSeverity {
@@ -224,6 +225,10 @@ export class CompilerError extends Error {
     return this.details.length > 0;
   }
 
+  asResult(): Result<void, CompilerError> {
+    return this.hasErrors() ? Err(this) : Ok(undefined);
+  }
+
   /*
    * An error is critical if it means the compiler has entered into a broken state and cannot
    * continue safely. Other expected errors such as Todos mean that we can skip over that component

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Gating.ts

@@ -7,8 +7,9 @@
 
 import {NodePath} from '@babel/core';
 import * as t from '@babel/types';
-import {PluginOptions} from './Options';
 import {CompilerError} from '../CompilerError';
+import {ProgramContext} from './Imports';
+import {ExternalFunction} from '..';
 
 /**
  * Gating rewrite for function declarations which are referenced before their
@@ -34,7 +35,8 @@ import {CompilerError} from '../CompilerError';
 function insertAdditionalFunctionDeclaration(
   fnPath: NodePath<t.FunctionDeclaration>,
   compiled: t.FunctionDeclaration,
-  gating: NonNullable<PluginOptions['gating']>,
+  programContext: ProgramContext,
+  gatingFunctionIdentifierName: string,
 ): void {
   const originalFnName = fnPath.node.id;
   const originalFnParams = fnPath.node.params;
@@ -57,14 +59,14 @@ function insertAdditionalFunctionDeclaration(
     loc: fnPath.node.loc ?? null,
   });
 
-  const gatingCondition = fnPath.scope.generateUidIdentifier(
-    `${gating.importSpecifierName}_result`,
+  const gatingCondition = t.identifier(
+    programContext.newUid(`${gatingFunctionIdentifierName}_result`),
   );
-  const unoptimizedFnName = fnPath.scope.generateUidIdentifier(
-    `${originalFnName.name}_unoptimized`,
+  const unoptimizedFnName = t.identifier(
+    programContext.newUid(`${originalFnName.name}_unoptimized`),
   );
-  const optimizedFnName = fnPath.scope.generateUidIdentifier(
-    `${originalFnName.name}_optimized`,
+  const optimizedFnName = t.identifier(
+    programContext.newUid(`${originalFnName.name}_optimized`),
   );
   /**
    * Step 1: rename existing functions
@@ -115,7 +117,7 @@ function insertAdditionalFunctionDeclaration(
     t.variableDeclaration('const', [
       t.variableDeclarator(
         gatingCondition,
-        t.callExpression(t.identifier(gating.importSpecifierName), []),
+        t.callExpression(t.identifier(gatingFunctionIdentifierName), []),
       ),
     ]),
   );
@@ -129,19 +131,26 @@ export function insertGatedFunctionDeclaration(
     | t.FunctionDeclaration
     | t.ArrowFunctionExpression
     | t.FunctionExpression,
-  gating: NonNullable<PluginOptions['gating']>,
+  programContext: ProgramContext,
+  gating: ExternalFunction,
   referencedBeforeDeclaration: boolean,
 ): void {
+  const gatingImportedName = programContext.addImportSpecifier(gating).name;
   if (referencedBeforeDeclaration && fnPath.isFunctionDeclaration()) {
     CompilerError.invariant(compiled.type === 'FunctionDeclaration', {
       reason: 'Expected compiled node type to match input type',
       description: `Got ${compiled.type} but expected FunctionDeclaration`,
       loc: fnPath.node.loc ?? null,
     });
-    insertAdditionalFunctionDeclaration(fnPath, compiled, gating);
+    insertAdditionalFunctionDeclaration(
+      fnPath,
+      compiled,
+      programContext,
+      gatingImportedName,
+    );
   } else {
     const gatingExpression = t.conditionalExpression(
-      t.callExpression(t.identifier(gating.importSpecifierName), []),
+      t.callExpression(t.identifier(gatingImportedName), []),
       buildFunctionExpression(compiled),
       buildFunctionExpression(fnPath.node),
     );

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Imports.ts

@@ -7,9 +7,20 @@
 
 import {NodePath} from '@babel/core';
 import * as t from '@babel/types';
+import {Scope as BabelScope} from '@babel/traverse';
+
 import {CompilerError, ErrorSeverity} from '../CompilerError';
-import {EnvironmentConfig, ExternalFunction, GeneratedSource} from '../HIR';
-import {getOrInsertDefault} from '../Utils/utils';
+import {
+  EnvironmentConfig,
+  GeneratedSource,
+  NonLocalImportSpecifier,
+} from '../HIR';
+import {getOrInsertWith} from '../Utils/utils';
+import {ExternalFunction, isHookName} from '../HIR/Environment';
+import {Err, Ok, Result} from '../Utils/Result';
+import {LoggerEvent, PluginOptions} from './Options';
+import {BabelFn, getReactCompilerRuntimeModule} from './Program';
+import {SuppressionRange} from './Suppression';
 
 export function validateRestrictedImports(
   path: NodePath<t.Program>,
@@ -42,50 +53,248 @@ export function validateRestrictedImports(
   }
 }
 
-export function addImportsToProgram(
-  path: NodePath<t.Program>,
-  importList: Array<ExternalFunction>,
-): void {
-  const identifiers: Set<string> = new Set();
-  const sortedImports: Map<string, Array<string>> = new Map();
-  for (const {importSpecifierName, source} of importList) {
-    /*
-     * Codegen currently does not rename import specifiers, so we do additional
-     * validation here
-     */
-    CompilerError.invariant(identifiers.has(importSpecifierName) === false, {
-      reason: `Encountered conflicting import specifier for ${importSpecifierName} in Forget config.`,
-      description: null,
-      loc: GeneratedSource,
-      suggestions: null,
-    });
-    CompilerError.invariant(
-      path.scope.hasBinding(importSpecifierName) === false,
-      {
-        reason: `Encountered conflicting import specifiers for ${importSpecifierName} in generated program.`,
-        description: null,
-        loc: GeneratedSource,
-        suggestions: null,
-      },
-    );
-    identifiers.add(importSpecifierName);
+type ProgramContextOptions = {
+  program: NodePath<t.Program>;
+  suppressions: Array<SuppressionRange>;
+  opts: PluginOptions;
+  filename: string | null;
+  code: string | null;
+  hasModuleScopeOptOut: boolean;
+};
+export class ProgramContext {
+  /**
+   * Program and environment context
+   */
+  scope: BabelScope;
+  opts: PluginOptions;
+  filename: string | null;
+  code: string | null;
+  reactRuntimeModule: string;
+  suppressions: Array<SuppressionRange>;
+  hasModuleScopeOptOut: boolean;
 
-    const importSpecifierNameList = getOrInsertDefault(
-      sortedImports,
-      source,
-      [],
-    );
-    importSpecifierNameList.push(importSpecifierName);
+  /*
+   * This is a hack to work around what seems to be a Babel bug. Babel doesn't
+   * consistently respect the `skip()` function to avoid revisiting a node within
+   * a pass, so we use this set to track nodes that we have compiled.
+   */
+  alreadyCompiled: WeakSet<object> | Set<object> = new (WeakSet ?? Set)();
+  // known generated or referenced identifiers in the program
+  knownReferencedNames: Set<string> = new Set();
+  // generated imports
+  imports: Map<string, Map<string, NonLocalImportSpecifier>> = new Map();
+
+  /**
+   * Metadata from compilation
+   */
+  retryErrors: Array<{fn: BabelFn; error: CompilerError}> = [];
+  inferredEffectLocations: Set<t.SourceLocation> = new Set();
+
+  constructor({
+    program,
+    suppressions,
+    opts,
+    filename,
+    code,
+    hasModuleScopeOptOut,
+  }: ProgramContextOptions) {
+    this.scope = program.scope;
+    this.opts = opts;
+    this.filename = filename;
+    this.code = code;
+    this.reactRuntimeModule = getReactCompilerRuntimeModule(opts.target);
+    this.suppressions = suppressions;
+    this.hasModuleScopeOptOut = hasModuleScopeOptOut;
   }
 
+  isHookName(name: string): boolean {
+    if (this.opts.environment.hookPattern == null) {
+      return isHookName(name);
+    } else {
+      const match = new RegExp(this.opts.environment.hookPattern).exec(name);
+      return (
+        match != null && typeof match[1] === 'string' && isHookName(match[1])
+      );
+    }
+  }
+
+  hasReference(name: string): boolean {
+    return (
+      this.knownReferencedNames.has(name) ||
+      this.scope.hasBinding(name) ||
+      this.scope.hasGlobal(name) ||
+      this.scope.hasReference(name)
+    );
+  }
+
+  newUid(name: string): string {
+    /**
+     * Don't call babel's generateUid for known hook imports, as
+     * InferTypes might eventually type `HookKind` based on callee naming
+     * convention and `_useFoo` is not named as a hook.
+     *
+     * Local uid generation is susceptible to check-before-use bugs since we're
+     * checking for naming conflicts / references long before we actually insert
+     * the import. (see similar logic in HIRBuilder:resolveBinding)
+     */
+    let uid;
+    if (this.isHookName(name)) {
+      uid = name;
+      let i = 0;
+      while (this.hasReference(uid)) {
+        this.knownReferencedNames.add(uid);
+        uid = `${name}_${i++}`;
+      }
+    } else if (!this.hasReference(name)) {
+      uid = name;
+    } else {
+      uid = this.scope.generateUid(name);
+    }
+    this.knownReferencedNames.add(uid);
+    return uid;
+  }
+
+  addMemoCacheImport(): NonLocalImportSpecifier {
+    return this.addImportSpecifier(
+      {
+        source: this.reactRuntimeModule,
+        importSpecifierName: 'c',
+      },
+      '_c',
+    );
+  }
+
+  /**
+   *
+   * @param externalFunction
+   * @param nameHint if defined, will be used as the name of the import specifier
+   * @returns
+   */
+  addImportSpecifier(
+    {source: module, importSpecifierName: specifier}: ExternalFunction,
+    nameHint?: string,
+  ): NonLocalImportSpecifier {
+    const maybeBinding = this.imports.get(module)?.get(specifier);
+    if (maybeBinding != null) {
+      return {...maybeBinding};
+    }
+
+    const binding: NonLocalImportSpecifier = {
+      kind: 'ImportSpecifier',
+      name: this.newUid(nameHint ?? specifier),
+      module,
+      imported: specifier,
+    };
+    getOrInsertWith(this.imports, module, () => new Map()).set(specifier, {
+      ...binding,
+    });
+    return binding;
+  }
+
+  addNewReference(name: string): void {
+    this.knownReferencedNames.add(name);
+  }
+
+  assertGlobalBinding(
+    name: string,
+    localScope?: BabelScope,
+  ): Result<void, CompilerError> {
+    const scope = localScope ?? this.scope;
+    if (!scope.hasReference(name) && !scope.hasBinding(name)) {
+      return Ok(undefined);
+    }
+    const error = new CompilerError();
+    error.push({
+      severity: ErrorSeverity.Todo,
+      reason: 'Encountered conflicting global in generated program',
+      description: `Conflict from local binding ${name}`,
+      loc: scope.getBinding(name)?.path.node.loc ?? null,
+      suggestions: null,
+    });
+    return Err(error);
+  }
+
+  logEvent(event: LoggerEvent): void {
+    if (this.opts.logger != null) {
+      this.opts.logger.logEvent(this.filename, event);
+    }
+  }
+}
+
+function getExistingImports(
+  program: NodePath<t.Program>,
+): Map<string, NodePath<t.ImportDeclaration>> {
+  const existingImports = new Map<string, NodePath<t.ImportDeclaration>>();
+  program.traverse({
+    ImportDeclaration(path) {
+      if (isNonNamespacedImport(path)) {
+        existingImports.set(path.node.source.value, path);
+      }
+    },
+  });
+  return existingImports;
+}
+
+export function addImportsToProgram(
+  path: NodePath<t.Program>,
+  programContext: ProgramContext,
+): void {
+  const existingImports = getExistingImports(path);
   const stmts: Array<t.ImportDeclaration> = [];
-  for (const [source, importSpecifierNameList] of sortedImports) {
-    const importSpecifiers = importSpecifierNameList.map(name => {
-      const id = t.identifier(name);
-      return t.importSpecifier(id, id);
+  const sortedModules = [...programContext.imports.entries()].sort(([a], [b]) =>
+    a.localeCompare(b),
+  );
+  for (const [moduleName, importsMap] of sortedModules) {
+    for (const [specifierName, loweredImport] of importsMap) {
+      /**
+       * Assert that the import identifier hasn't already be declared in the program.
+       * Note: we use getBinding here since `Scope.hasBinding` pessimistically returns true
+       * for all allocated uids (from `Scope.getUid`)
+       */
+      CompilerError.invariant(
+        path.scope.getBinding(loweredImport.name) == null,
+        {
+          reason:
+            'Encountered conflicting import specifiers in generated program',
+          description: `Conflict from import ${loweredImport.module}:(${loweredImport.imported} as ${loweredImport.name}).`,
+          loc: GeneratedSource,
+          suggestions: null,
+        },
+      );
+      CompilerError.invariant(
+        loweredImport.module === moduleName &&
+          loweredImport.imported === specifierName,
+        {
+          reason:
+            'Found inconsistent import specifier. This is an internal bug.',
+          description: `Expected import ${moduleName}:${specifierName} but found ${loweredImport.module}:${loweredImport.imported}`,
+          loc: GeneratedSource,
+        },
+      );
+    }
+    const sortedImport: Array<NonLocalImportSpecifier> = [
+      ...importsMap.values(),
+    ].sort(({imported: a}, {imported: b}) => a.localeCompare(b));
+    const importSpecifiers = sortedImport.map(specifier => {
+      return t.importSpecifier(
+        t.identifier(specifier.name),
+        t.identifier(specifier.imported),
+      );
     });
 
-    stmts.push(t.importDeclaration(importSpecifiers, t.stringLiteral(source)));
+    /**
+     * If an existing import of this module exists (ie `import { ... } from
+     * '<moduleName>'`), inject new imported specifiers into the list of
+     * destructured variables.
+     */
+    const maybeExistingImports = existingImports.get(moduleName);
+    if (maybeExistingImports != null) {
+      maybeExistingImports.pushContainer('specifiers', importSpecifiers);
+    } else {
+      stmts.push(
+        t.importDeclaration(importSpecifiers, t.stringLiteral(moduleName)),
+      );
+    }
   }
   path.unshiftContainer('body', stmts);
 }
@@ -93,13 +302,12 @@ export function addImportsToProgram(
 /*
  * Matches `import { ... } from <moduleName>;`
  * but not `import * as React from <moduleName>;`
+ *         `import type { Foo } from <moduleName>;`
  */
 function isNonNamespacedImport(
   importDeclPath: NodePath<t.ImportDeclaration>,
-  moduleName: string,
 ): boolean {
   return (
-    importDeclPath.get('source').node.value === moduleName &&
     importDeclPath
       .get('specifiers')
       .every(specifier => specifier.isImportSpecifier()) &&
@@ -107,94 +315,3 @@ function isNonNamespacedImport(
     importDeclPath.node.importKind !== 'typeof'
   );
 }
-
-function hasExistingNonNamespacedImportOfModule(
-  program: NodePath<t.Program>,
-  moduleName: string,
-): boolean {
-  let hasExistingImport = false;
-  program.traverse({
-    ImportDeclaration(importDeclPath) {
-      if (isNonNamespacedImport(importDeclPath, moduleName)) {
-        hasExistingImport = true;
-      }
-    },
-  });
-
-  return hasExistingImport;
-}
-
-/*
- * If an existing import of React exists (ie `import { ... } from '<moduleName>'`), inject useMemoCache
- * into the list of destructured variables.
- */
-function addMemoCacheFunctionSpecifierToExistingImport(
-  program: NodePath<t.Program>,
-  moduleName: string,
-  identifierName: string,
-): boolean {
-  let didInsertUseMemoCache = false;
-  program.traverse({
-    ImportDeclaration(importDeclPath) {
-      if (
-        !didInsertUseMemoCache &&
-        isNonNamespacedImport(importDeclPath, moduleName)
-      ) {
-        importDeclPath.pushContainer(
-          'specifiers',
-          t.importSpecifier(t.identifier(identifierName), t.identifier('c')),
-        );
-        didInsertUseMemoCache = true;
-      }
-    },
-  });
-  return didInsertUseMemoCache;
-}
-
-export function updateMemoCacheFunctionImport(
-  program: NodePath<t.Program>,
-  moduleName: string,
-  useMemoCacheIdentifier: string,
-): void {
-  /*
-   * If there isn't already an import of * as React, insert it so useMemoCache doesn't
-   * throw
-   */
-  const hasExistingImport = hasExistingNonNamespacedImportOfModule(
-    program,
-    moduleName,
-  );
-
-  if (hasExistingImport) {
-    const didUpdateImport = addMemoCacheFunctionSpecifierToExistingImport(
-      program,
-      moduleName,
-      useMemoCacheIdentifier,
-    );
-    if (!didUpdateImport) {
-      throw new Error(
-        `Expected an ImportDeclaration of \`${moduleName}\` in order to update ImportSpecifiers with useMemoCache`,
-      );
-    }
-  } else {
-    addMemoCacheFunctionImportDeclaration(
-      program,
-      moduleName,
-      useMemoCacheIdentifier,
-    );
-  }
-}
-
-function addMemoCacheFunctionImportDeclaration(
-  program: NodePath<t.Program>,
-  moduleName: string,
-  localName: string,
-): void {
-  program.unshiftContainer(
-    'body',
-    t.importDeclaration(
-      [t.importSpecifier(t.identifier(localName), t.identifier('c'))],
-      t.stringLiteral(moduleName),
-    ),
-  );
-}

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Options.ts

@@ -37,6 +37,14 @@ const PanicThresholdOptionsSchema = z.enum([
 ]);
 
 export type PanicThresholdOptions = z.infer<typeof PanicThresholdOptionsSchema>;
+const DynamicGatingOptionsSchema = z.object({
+  source: z.string(),
+});
+export type DynamicGatingOptions = z.infer<typeof DynamicGatingOptionsSchema>;
+const CustomOptOutDirectiveSchema = z
+  .nullable(z.array(z.string()))
+  .default(null);
+type CustomOptOutDirective = z.infer<typeof CustomOptOutDirectiveSchema>;
 
 export type PluginOptions = {
   environment: EnvironmentConfig;
@@ -65,6 +73,28 @@ export type PluginOptions = {
    */
   gating: ExternalFunction | null;
 
+  /**
+   * If specified, this enables dynamic gating which matches `use memo if(...)`
+   * directives.
+   *
+   * Example usage:
+   * ```js
+   * // @dynamicGating:{"source":"myModule"}
+   * export function MyComponent() {
+   *   'use memo if(isEnabled)';
+   *    return <div>...</div>;
+   * }
+   * ```
+   * This will emit:
+   * ```js
+   * import {isEnabled} from 'myModule';
+   * export const MyComponent = isEnabled()
+   *   ? <optimized version>
+   *   : <original version>;
+   * ```
+   */
+  dynamicGating: DynamicGatingOptions | null;
+
   panicThreshold: PanicThresholdOptions;
 
   /*
@@ -98,7 +128,7 @@ export type PluginOptions = {
    * provided rules will skip compilation. To disable this feature (never bailout of compilation
    * even if the default ESLint is suppressed), pass an empty array.
    */
-  eslintSuppressionRules?: Array<string> | null | undefined;
+  eslintSuppressionRules: Array<string> | null | undefined;
 
   flowSuppressions: boolean;
   /*
@@ -106,7 +136,12 @@ export type PluginOptions = {
    */
   ignoreUseNoForget: boolean;
 
-  sources?: Array<string> | ((filename: string) => boolean) | null;
+  /**
+   * Unstable / do not use
+   */
+  customOptOutDirectives: CustomOptOutDirective;
+
+  sources: Array<string> | ((filename: string) => boolean) | null;
 
   /**
    * The compiler has customized support for react-native-reanimated, intended as a temporary workaround.
@@ -182,7 +217,9 @@ export type LoggerEvent =
   | CompileDiagnosticEvent
   | CompileSkipEvent
   | PipelineErrorEvent
-  | TimingEvent;
+  | TimingEvent
+  | AutoDepsDecorationsEvent
+  | AutoDepsEligibleEvent;
 
 export type CompileErrorEvent = {
   kind: 'CompileError';
@@ -219,6 +256,16 @@ export type TimingEvent = {
   kind: 'Timing';
   measurement: PerformanceMeasure;
 };
+export type AutoDepsDecorationsEvent = {
+  kind: 'AutoDepsDecorations';
+  fnLoc: t.SourceLocation;
+  decorations: Array<t.SourceLocation>;
+};
+export type AutoDepsEligibleEvent = {
+  kind: 'AutoDepsEligible';
+  fnLoc: t.SourceLocation;
+  depArrayLoc: t.SourceLocation;
+};
 
 export type Logger = {
   logEvent: (filename: string | null, event: LoggerEvent) => void;
@@ -232,6 +279,7 @@ export const defaultOptions: PluginOptions = {
   logger: null,
   gating: null,
   noEmit: false,
+  dynamicGating: null,
   eslintSuppressionRules: null,
   flowSuppressions: true,
   ignoreUseNoForget: false,
@@ -239,6 +287,7 @@ export const defaultOptions: PluginOptions = {
     return filename.indexOf('node_modules') === -1;
   },
   enableReanimatedCheck: true,
+  customOptOutDirectives: null,
   target: '19',
 } as const;
 
@@ -280,6 +329,40 @@ export function parsePluginOptions(obj: unknown): PluginOptions {
           }
           break;
         }
+        case 'dynamicGating': {
+          if (value == null) {
+            parsedOptions[key] = null;
+          } else {
+            const result = DynamicGatingOptionsSchema.safeParse(value);
+            if (result.success) {
+              parsedOptions[key] = result.data;
+            } else {
+              CompilerError.throwInvalidConfig({
+                reason:
+                  'Could not parse dynamic gating. Update React Compiler config to fix the error',
+                description: `${fromZodError(result.error)}`,
+                loc: null,
+                suggestions: null,
+              });
+            }
+          }
+          break;
+        }
+        case 'customOptOutDirectives': {
+          const result = CustomOptOutDirectiveSchema.safeParse(value);
+          if (result.success) {
+            parsedOptions[key] = result.data;
+          } else {
+            CompilerError.throwInvalidConfig({
+              reason:
+                'Could not parse custom opt out directives. Update React Compiler config to fix the error',
+              description: `${fromZodError(result.error)}`,
+              loc: null,
+              suggestions: null,
+            });
+          }
+          break;
+        }
         default: {
           parsedOptions[key] = value;
         }

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Pipeline.ts

@@ -8,7 +8,7 @@
 import {NodePath} from '@babel/traverse';
 import * as t from '@babel/types';
 import prettyFormat from 'pretty-format';
-import {Logger} from '.';
+import {Logger, ProgramContext} from '.';
 import {
   HIRFunction,
   ReactiveFunction,
@@ -100,8 +100,12 @@ import {propagateScopeDependenciesHIR} from '../HIR/PropagateScopeDependenciesHI
 import {outlineJSX} from '../Optimization/OutlineJsx';
 import {optimizePropsMethodCalls} from '../Optimization/OptimizePropsMethodCalls';
 import {transformFire} from '../Transform';
-import {validateNoImpureFunctionsInRender} from '../Validation/ValiateNoImpureFunctionsInRender';
+import {validateNoImpureFunctionsInRender} from '../Validation/ValidateNoImpureFunctionsInRender';
 import {CompilerError} from '..';
+import {validateStaticComponents} from '../Validation/ValidateStaticComponents';
+import {validateNoFreezingKnownMutableFunctions} from '../Validation/ValidateNoFreezingKnownMutableFunctions';
+import {inferMutationAliasingEffects} from '../Inference/InferMutationAliasingEffects';
+import {inferMutationAliasingRanges} from '../Inference/InferMutationAliasingRanges';
 
 export type CompilerPipelineValue =
   | {kind: 'ast'; name: string; value: CodegenFunction}
@@ -116,7 +120,7 @@ function run(
   config: EnvironmentConfig,
   fnType: ReactFunctionType,
   mode: CompilerMode,
-  useMemoCacheIdentifier: string,
+  programContext: ProgramContext,
   logger: Logger | null,
   filename: string | null,
   code: string | null,
@@ -128,10 +132,11 @@ function run(
     mode,
     config,
     contextIdentifiers,
+    func,
     logger,
     filename,
     code,
-    useMemoCacheIdentifier,
+    programContext,
   );
   env.logger?.debugLogIRs?.({
     kind: 'debug',
@@ -161,7 +166,7 @@ function runWithEnvironment(
   log({kind: 'hir', name: 'PruneMaybeThrows', value: hir});
 
   validateContextVariableLValues(hir);
-  validateUseMemo(hir);
+  validateUseMemo(hir).unwrap();
 
   if (
     env.isInferredMemoEnabled &&
@@ -202,10 +207,10 @@ function runWithEnvironment(
 
   if (env.isInferredMemoEnabled) {
     if (env.config.validateHooksUsage) {
-      validateHooksUsage(hir);
+      validateHooksUsage(hir).unwrap();
     }
     if (env.config.validateNoCapitalizedCalls) {
-      validateNoCapitalizedCalls(hir);
+      validateNoCapitalizedCalls(hir).unwrap();
     }
   }
 
@@ -224,15 +229,27 @@ function runWithEnvironment(
   analyseFunctions(hir);
   log({kind: 'hir', name: 'AnalyseFunctions', value: hir});
 
-  const fnEffectErrors = inferReferenceEffects(hir);
-  if (env.isInferredMemoEnabled) {
-    if (fnEffectErrors.length > 0) {
-      CompilerError.throw(fnEffectErrors[0]);
+  if (!env.config.enableNewMutationAliasingModel) {
+    const fnEffectErrors = inferReferenceEffects(hir);
+    if (env.isInferredMemoEnabled) {
+      if (fnEffectErrors.length > 0) {
+        CompilerError.throw(fnEffectErrors[0]);
+      }
+    }
+    log({kind: 'hir', name: 'InferReferenceEffects', value: hir});
+  } else {
+    const mutabilityAliasingErrors = inferMutationAliasingEffects(hir);
+    log({kind: 'hir', name: 'InferMutationAliasingEffects', value: hir});
+    if (env.isInferredMemoEnabled) {
+      if (mutabilityAliasingErrors.isErr()) {
+        throw mutabilityAliasingErrors.unwrapErr();
+      }
     }
   }
-  log({kind: 'hir', name: 'InferReferenceEffects', value: hir});
 
-  validateLocalsNotReassignedAfterRender(hir);
+  if (!env.config.enableNewMutationAliasingModel) {
+    validateLocalsNotReassignedAfterRender(hir);
+  }
 
   // Note: Has to come after infer reference effects because "dead" code may still affect inference
   deadCodeElimination(hir);
@@ -246,8 +263,21 @@ function runWithEnvironment(
   pruneMaybeThrows(hir);
   log({kind: 'hir', name: 'PruneMaybeThrows', value: hir});
 
-  inferMutableRanges(hir);
-  log({kind: 'hir', name: 'InferMutableRanges', value: hir});
+  if (!env.config.enableNewMutationAliasingModel) {
+    inferMutableRanges(hir);
+    log({kind: 'hir', name: 'InferMutableRanges', value: hir});
+  } else {
+    const mutabilityAliasingErrors = inferMutationAliasingRanges(hir, {
+      isFunctionExpression: false,
+    });
+    log({kind: 'hir', name: 'InferMutationAliasingRanges', value: hir});
+    if (env.isInferredMemoEnabled) {
+      if (mutabilityAliasingErrors.isErr()) {
+        throw mutabilityAliasingErrors.unwrapErr();
+      }
+      validateLocalsNotReassignedAfterRender(hir);
+    }
+  }
 
   if (env.isInferredMemoEnabled) {
     if (env.config.assertValidMutableRanges) {
@@ -255,23 +285,30 @@ function runWithEnvironment(
     }
 
     if (env.config.validateRefAccessDuringRender) {
-      validateNoRefAccessInRender(hir);
+      validateNoRefAccessInRender(hir).unwrap();
     }
 
     if (env.config.validateNoSetStateInRender) {
-      validateNoSetStateInRender(hir);
+      validateNoSetStateInRender(hir).unwrap();
     }
 
     if (env.config.validateNoSetStateInPassiveEffects) {
-      validateNoSetStateInPassiveEffects(hir);
+      env.logErrors(validateNoSetStateInPassiveEffects(hir));
     }
 
     if (env.config.validateNoJSXInTryStatements) {
-      validateNoJSXInTryStatement(hir);
+      env.logErrors(validateNoJSXInTryStatement(hir));
     }
 
     if (env.config.validateNoImpureFunctionsInRender) {
-      validateNoImpureFunctionsInRender(hir);
+      validateNoImpureFunctionsInRender(hir).unwrap();
+    }
+
+    if (
+      env.config.validateNoFreezingKnownMutableFunctions ||
+      env.config.enableNewMutationAliasingModel
+    ) {
+      validateNoFreezingKnownMutableFunctions(hir).unwrap();
     }
   }
 
@@ -293,6 +330,10 @@ function runWithEnvironment(
   });
 
   if (env.isInferredMemoEnabled) {
+    if (env.config.validateStaticComponents) {
+      env.logErrors(validateStaticComponents(hir));
+    }
+
     /**
      * Only create reactive scopes (which directly map to generated memo blocks)
      * if inferred memoization is enabled. This makes all later passes which
@@ -387,6 +428,11 @@ function runWithEnvironment(
 
   if (env.config.inferEffectDependencies) {
     inferEffectDependencies(hir);
+    log({
+      kind: 'hir',
+      name: 'InferEffectDependencies',
+      value: hir,
+    });
   }
 
   if (env.config.inlineJsxTransform) {
@@ -509,14 +555,14 @@ function runWithEnvironment(
   });
 
   if (env.config.validateMemoizedEffectDependencies) {
-    validateMemoizedEffectDependencies(reactiveFunction);
+    validateMemoizedEffectDependencies(reactiveFunction).unwrap();
   }
 
   if (
     env.config.enablePreserveExistingMemoizationGuarantees ||
     env.config.validatePreserveExistingMemoizationGuarantees
   ) {
-    validatePreservedManualMemoization(reactiveFunction);
+    validatePreservedManualMemoization(reactiveFunction).unwrap();
   }
 
   const ast = codegenFunction(reactiveFunction, {
@@ -547,7 +593,7 @@ export function compileFn(
   config: EnvironmentConfig,
   fnType: ReactFunctionType,
   mode: CompilerMode,
-  useMemoCacheIdentifier: string,
+  programContext: ProgramContext,
   logger: Logger | null,
   filename: string | null,
   code: string | null,
@@ -557,7 +603,7 @@ export function compileFn(
     config,
     fnType,
     mode,
-    useMemoCacheIdentifier,
+    programContext,
     logger,
     filename,
     code,

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Reanimated.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import type * as BabelCore from '@babel/core';
 import {hasOwnProperty} from '../Utils/utils';
 import {PluginOptions} from './Options';

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/ValidateNoUntransformedReferences.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {NodePath} from '@babel/core';
 import * as t from '@babel/types';
 
@@ -11,6 +18,7 @@ import {
 import {getOrInsertWith} from '../Utils/utils';
 import {Environment} from '../HIR';
 import {DEFAULT_EXPORT} from '../HIR/Environment';
+import {CompileProgramMetadata} from './Program';
 
 function throwInvalidReact(
   options: Omit<CompilerErrorDetailOptions, 'severity'>,
@@ -36,12 +44,16 @@ function assertValidEffectImportReference(
     const parent = path.parentPath;
     if (parent != null && parent.isCallExpression()) {
       const args = parent.get('arguments');
+      const maybeCalleeLoc = path.node.loc;
+      const hasInferredEffect =
+        maybeCalleeLoc != null &&
+        context.inferredEffectLocations.has(maybeCalleeLoc);
       /**
        * Only error on untransformed references of the form `useMyEffect(...)`
        * or `moduleNamespace.useMyEffect(...)`, with matching argument counts.
        * TODO: do we also want a mode to also hard error on non-call references?
        */
-      if (args.length === numArgs) {
+      if (args.length === numArgs && !hasInferredEffect) {
         const maybeErrorDiagnostic = matchCompilerDiagnostic(
           path,
           context.transformErrors,
@@ -97,7 +109,7 @@ export default function validateNoUntransformedReferences(
   filename: string | null,
   logger: Logger | null,
   env: EnvironmentConfig,
-  transformErrors: Array<{fn: NodePath<t.Node>; error: CompilerError}>,
+  compileResult: CompileProgramMetadata | null,
 ): void {
   const moduleLoadChecks = new Map<
     string,
@@ -126,7 +138,7 @@ export default function validateNoUntransformedReferences(
     }
   }
   if (moduleLoadChecks.size > 0) {
-    transformProgram(path, moduleLoadChecks, filename, logger, transformErrors);
+    transformProgram(path, moduleLoadChecks, filename, logger, compileResult);
   }
 }
 
@@ -136,6 +148,7 @@ type TraversalState = {
   logger: Logger | null;
   filename: string | null;
   transformErrors: Array<{fn: NodePath<t.Node>; error: CompilerError}>;
+  inferredEffectLocations: Set<t.SourceLocation>;
 };
 type CheckInvalidReferenceFn = (
   paths: Array<NodePath<t.Node>>,
@@ -223,14 +236,16 @@ function transformProgram(
   moduleLoadChecks: Map<string, Map<string, CheckInvalidReferenceFn>>,
   filename: string | null,
   logger: Logger | null,
-  transformErrors: Array<{fn: NodePath<t.Node>; error: CompilerError}>,
+  compileResult: CompileProgramMetadata | null,
 ): void {
   const traversalState: TraversalState = {
     shouldInvalidateScopes: true,
     program: path,
     filename,
     logger,
-    transformErrors,
+    transformErrors: compileResult?.retryErrors ?? [],
+    inferredEffectLocations:
+      compileResult?.inferredEffectLocations ?? new Set(),
   };
   path.traverse({
     ImportDeclaration(path: NodePath<t.ImportDeclaration>) {

compiler/packages/babel-plugin-react-compiler/src/HIR/AssertValidBlockNesting.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '..';
 import {
   BlockId,

compiler/packages/babel-plugin-react-compiler/src/HIR/AssertValidMutableRanges.ts

@@ -5,13 +5,14 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import invariant from 'invariant';
-import {HIRFunction, Identifier, MutableRange} from './HIR';
+import {HIRFunction, MutableRange, Place} from './HIR';
 import {
   eachInstructionLValue,
   eachInstructionOperand,
   eachTerminalOperand,
 } from './visitors';
+import {CompilerError} from '..';
+import {printPlace} from './PrintHIR';
 
 /*
  * Checks that all mutable ranges in the function are well-formed, with
@@ -20,38 +21,43 @@ import {
 export function assertValidMutableRanges(fn: HIRFunction): void {
   for (const [, block] of fn.body.blocks) {
     for (const phi of block.phis) {
-      visitIdentifier(phi.place.identifier);
-      for (const [, operand] of phi.operands) {
-        visitIdentifier(operand.identifier);
+      visit(phi.place, `phi for block bb${block.id}`);
+      for (const [pred, operand] of phi.operands) {
+        visit(operand, `phi predecessor bb${pred} for block bb${block.id}`);
       }
     }
     for (const instr of block.instructions) {
       for (const operand of eachInstructionLValue(instr)) {
-        visitIdentifier(operand.identifier);
+        visit(operand, `instruction [${instr.id}]`);
       }
       for (const operand of eachInstructionOperand(instr)) {
-        visitIdentifier(operand.identifier);
+        visit(operand, `instruction [${instr.id}]`);
       }
     }
     for (const operand of eachTerminalOperand(block.terminal)) {
-      visitIdentifier(operand.identifier);
+      visit(operand, `terminal [${block.terminal.id}]`);
     }
   }
 }
 
-function visitIdentifier(identifier: Identifier): void {
-  validateMutableRange(identifier.mutableRange);
-  if (identifier.scope !== null) {
-    validateMutableRange(identifier.scope.range);
+function visit(place: Place, description: string): void {
+  validateMutableRange(place, place.identifier.mutableRange, description);
+  if (place.identifier.scope !== null) {
+    validateMutableRange(place, place.identifier.scope.range, description);
   }
 }
 
-function validateMutableRange(mutableRange: MutableRange): void {
-  invariant(
-    (mutableRange.start === 0 && mutableRange.end === 0) ||
-      mutableRange.end > mutableRange.start,
-    'Identifier scope mutableRange was invalid: [%s:%s]',
-    mutableRange.start,
-    mutableRange.end,
+function validateMutableRange(
+  place: Place,
+  range: MutableRange,
+  description: string,
+): void {
+  CompilerError.invariant(
+    (range.start === 0 && range.end === 0) || range.end > range.start,
+    {
+      reason: `Invalid mutable range: [${range.start}:${range.end}]`,
+      description: `${printPlace(place)} in ${description}`,
+      loc: place.loc,
+    },
   );
 }

compiler/packages/babel-plugin-react-compiler/src/HIR/BuildHIR.ts

@@ -47,7 +47,7 @@ import {
   makeType,
   promoteTemporary,
 } from './HIR';
-import HIRBuilder, {Bindings} from './HIRBuilder';
+import HIRBuilder, {Bindings, createTemporaryPlace} from './HIRBuilder';
 import {BuiltInArrayId} from './ObjectShape';
 
 /*
@@ -70,12 +70,14 @@ import {BuiltInArrayId} from './ObjectShape';
 export function lower(
   func: NodePath<t.Function>,
   env: Environment,
+  // Bindings captured from the outer function, in case lower() is called recursively (for lambdas)
   bindings: Bindings | null = null,
   capturedRefs: Array<t.Identifier> = [],
-  // the outermost function being compiled, in case lower() is called recursively (for lambdas)
-  parent: NodePath<t.Function> | null = null,
 ): Result<HIRFunction, CompilerError> {
-  const builder = new HIRBuilder(env, parent ?? func, bindings, capturedRefs);
+  const builder = new HIRBuilder(env, {
+    bindings,
+    context: capturedRefs,
+  });
   const context: HIRFunction['context'] = [];
 
   for (const ref of capturedRefs ?? []) {
@@ -179,6 +181,7 @@ export function lower(
       loc: GeneratedSource,
       value: lowerExpressionToTemporary(builder, body),
       id: makeInstructionId(0),
+      effects: null,
     };
     builder.terminateWithContinuation(terminal, fallthrough);
   } else if (body.isBlockStatement()) {
@@ -208,6 +211,7 @@ export function lower(
         loc: GeneratedSource,
       }),
       id: makeInstructionId(0),
+      effects: null,
     },
     null,
   );
@@ -215,9 +219,10 @@ export function lower(
   return Ok({
     id,
     params,
-    fnType: parent == null ? env.fnType : 'Other',
+    fnType: bindings == null ? env.fnType : 'Other',
     returnTypeAnnotation: null, // TODO: extract the actual return type node if present
     returnType: makeType(),
+    returns: createTemporaryPlace(env, func.node.loc ?? GeneratedSource),
     body: builder.build(),
     context,
     generator: func.node.generator === true,
@@ -225,6 +230,7 @@ export function lower(
     loc: func.node.loc ?? GeneratedSource,
     env,
     effects: null,
+    aliasingEffects: null,
     directives,
   });
 }
@@ -285,6 +291,7 @@ function lowerStatement(
         loc: stmt.node.loc ?? GeneratedSource,
         value,
         id: makeInstructionId(0),
+        effects: null,
       };
       builder.terminate(terminal, 'block');
       return;
@@ -1235,6 +1242,7 @@ function lowerStatement(
           kind: 'Debugger',
           loc,
         },
+        effects: null,
         loc,
       });
       return;
@@ -1892,6 +1900,7 @@ function lowerExpression(
           place: leftValue,
           loc: exprLoc,
         },
+        effects: null,
         loc: exprLoc,
       });
       builder.terminateWithContinuation(
@@ -2406,6 +2415,19 @@ function lowerExpression(
         kind: 'TypeCastExpression',
         value: lowerExpressionToTemporary(builder, expr.get('expression')),
         typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'cast',
+        type: lowerType(typeAnnotation.node),
+        loc: exprLoc,
+      };
+    }
+    case 'TSSatisfiesExpression': {
+      let expr = exprPath as NodePath<t.TSSatisfiesExpression>;
+      const typeAnnotation = expr.get('typeAnnotation');
+      return {
+        kind: 'TypeCastExpression',
+        value: lowerExpressionToTemporary(builder, expr.get('expression')),
+        typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'satisfies',
         type: lowerType(typeAnnotation.node),
         loc: exprLoc,
       };
@@ -2417,6 +2439,7 @@ function lowerExpression(
         kind: 'TypeCastExpression',
         value: lowerExpressionToTemporary(builder, expr.get('expression')),
         typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'as',
         type: lowerType(typeAnnotation.node),
         loc: exprLoc,
       };
@@ -2813,6 +2836,7 @@ function lowerOptionalCallExpression(
           args,
           loc,
         },
+        effects: null,
         loc,
       });
     } else {
@@ -2826,6 +2850,7 @@ function lowerOptionalCallExpression(
           args,
           loc,
         },
+        effects: null,
         loc,
       });
     }
@@ -3403,7 +3428,7 @@ function lowerFunction(
     | t.ObjectMethod
   >,
 ): LoweredFunction | null {
-  const componentScope: Scope = builder.parentFunction.scope;
+  const componentScope: Scope = builder.environment.parentFunction.scope;
   const capturedContext = gatherCapturedContext(expr, componentScope);
 
   /*
@@ -3414,13 +3439,10 @@ function lowerFunction(
    * This isn't a problem in practice because use Babel's scope analysis to
    * identify the correct references.
    */
-  const lowering = lower(
-    expr,
-    builder.environment,
-    builder.bindings,
-    [...builder.context, ...capturedContext],
-    builder.parentFunction,
-  );
+  const lowering = lower(expr, builder.environment, builder.bindings, [
+    ...builder.context,
+    ...capturedContext,
+  ]);
   let loweredFunc: HIRFunction;
   if (lowering.isErr()) {
     lowering
@@ -3442,7 +3464,7 @@ function lowerExpressionToTemporary(
   return lowerValueToTemporary(builder, value);
 }
 
-function lowerValueToTemporary(
+export function lowerValueToTemporary(
   builder: HIRBuilder,
   value: InstructionValue,
 ): Place {
@@ -3452,9 +3474,10 @@ function lowerValueToTemporary(
   const place: Place = buildTemporaryPlace(builder, value.loc);
   builder.push({
     id: makeInstructionId(0),
-    value: value,
-    loc: value.loc,
     lvalue: {...place},
+    value: value,
+    effects: null,
+    loc: value.loc,
   });
   return place;
 }
@@ -3595,31 +3618,40 @@ function lowerAssignment(
 
       let temporary;
       if (builder.isContextIdentifier(lvalue)) {
-        if (kind !== InstructionKind.Reassign && !isHoistedIdentifier) {
-          if (kind === InstructionKind.Const) {
-            builder.errors.push({
-              reason: `Expected \`const\` declaration not to be reassigned`,
-              severity: ErrorSeverity.InvalidJS,
-              loc: lvalue.node.loc ?? null,
-              suggestions: null,
-            });
-          }
-          lowerValueToTemporary(builder, {
-            kind: 'DeclareContext',
-            lvalue: {
-              kind: InstructionKind.Let,
-              place: {...place},
-            },
-            loc: place.loc,
+        if (kind === InstructionKind.Const && !isHoistedIdentifier) {
+          builder.errors.push({
+            reason: `Expected \`const\` declaration not to be reassigned`,
+            severity: ErrorSeverity.InvalidJS,
+            loc: lvalue.node.loc ?? null,
+            suggestions: null,
           });
         }
 
-        temporary = lowerValueToTemporary(builder, {
-          kind: 'StoreContext',
-          lvalue: {place: {...place}, kind: InstructionKind.Reassign},
-          value,
-          loc,
-        });
+        if (
+          kind !== InstructionKind.Const &&
+          kind !== InstructionKind.Reassign &&
+          kind !== InstructionKind.Let &&
+          kind !== InstructionKind.Function
+        ) {
+          builder.errors.push({
+            reason: `Unexpected context variable kind`,
+            severity: ErrorSeverity.InvalidJS,
+            loc: lvalue.node.loc ?? null,
+            suggestions: null,
+          });
+          temporary = lowerValueToTemporary(builder, {
+            kind: 'UnsupportedNode',
+            node: lvalueNode,
+            loc: lvalueNode.loc ?? GeneratedSource,
+          });
+        } else {
+          temporary = lowerValueToTemporary(builder, {
+            kind: 'StoreContext',
+            lvalue: {place: {...place}, kind},
+            value,
+            loc,
+          });
+        }
       } else {
         const typeAnnotation = lvalue.get('typeAnnotation');
         let type: t.FlowType | t.TSType | null;

compiler/packages/babel-plugin-react-compiler/src/HIR/BuildReactiveScopeTerminalsHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '../CompilerError';
 import {getScopes, recursivelyTraverseItems} from './AssertValidBlockNesting';
 import {Environment} from './Environment';

compiler/packages/babel-plugin-react-compiler/src/HIR/CollectHoistablePropertyLoads.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '../CompilerError';
 import {inRange} from '../ReactiveScopes/InferReactiveScopeVariables';
 import {printDependency} from '../ReactiveScopes/PrintReactiveFunction';
@@ -12,6 +19,7 @@ import {
   BasicBlock,
   BlockId,
   DependencyPathEntry,
+  FunctionExpression,
   GeneratedSource,
   getHookKind,
   HIRFunction,
@@ -23,6 +31,7 @@ import {
   PropertyLiteral,
   ReactiveScopeDependency,
   ScopeId,
+  TInstruction,
 } from './HIR';
 
 const DEBUG_PRINT = false;
@@ -120,6 +129,33 @@ export function collectHoistablePropertyLoads(
   });
 }
 
+export function collectHoistablePropertyLoadsInInnerFn(
+  fnInstr: TInstruction<FunctionExpression>,
+  temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>,
+  hoistableFromOptionals: ReadonlyMap<BlockId, ReactiveScopeDependency>,
+): ReadonlyMap<BlockId, BlockInfo> {
+  const fn = fnInstr.value.loweredFunc.func;
+  const initialContext: CollectHoistablePropertyLoadsContext = {
+    temporaries,
+    knownImmutableIdentifiers: new Set(),
+    hoistableFromOptionals,
+    registry: new PropertyPathRegistry(),
+    nestedFnImmutableContext: null,
+    assumedInvokedFns: fn.env.config.enableTreatFunctionDepsAsConditional
+      ? new Set()
+      : getAssumedInvokedFunctions(fn),
+  };
+  const nestedFnImmutableContext = new Set(
+    fn.context
+      .filter(place =>
+        isImmutableAtInstr(place.identifier, fnInstr.id, initialContext),
+      )
+      .map(place => place.identifier.id),
+  );
+  initialContext.nestedFnImmutableContext = nestedFnImmutableContext;
+  return collectHoistablePropertyLoadsImpl(fn, initialContext);
+}
+
 type CollectHoistablePropertyLoadsContext = {
   temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>;
   knownImmutableIdentifiers: ReadonlySet<IdentifierId>;
@@ -205,7 +241,10 @@ type PropertyPathNode =
 class PropertyPathRegistry {
   roots: Map<IdentifierId, RootNode> = new Map();
 
-  getOrCreateIdentifier(identifier: Identifier): PropertyPathNode {
+  getOrCreateIdentifier(
+    identifier: Identifier,
+    reactive: boolean,
+  ): PropertyPathNode {
     /**
      * Reads from a statically scoped variable are always safe in JS,
      * with the exception of TDZ (not addressed by this pass).
@@ -219,12 +258,19 @@ class PropertyPathRegistry {
         optionalProperties: new Map(),
         fullPath: {
           identifier,
+          reactive,
           path: [],
         },
         hasOptional: false,
         parent: null,
       };
       this.roots.set(identifier.id, rootNode);
+    } else {
+      CompilerError.invariant(reactive === rootNode.fullPath.reactive, {
+        reason:
+          '[HoistablePropertyLoads] Found inconsistencies in `reactive` flag when deduping identifier reads within the same scope',
+        loc: identifier.loc,
+      });
     }
     return rootNode;
   }
@@ -242,6 +288,7 @@ class PropertyPathRegistry {
         parent: parent,
         fullPath: {
           identifier: parent.fullPath.identifier,
+          reactive: parent.fullPath.reactive,
           path: parent.fullPath.path.concat(entry),
         },
         hasOptional: parent.hasOptional || entry.optional,
@@ -257,7 +304,7 @@ class PropertyPathRegistry {
      * so all subpaths of a PropertyLoad should already exist
      * (e.g. a.b is added before a.b.c),
      */
-    let currNode = this.getOrCreateIdentifier(n.identifier);
+    let currNode = this.getOrCreateIdentifier(n.identifier, n.reactive);
     if (n.path.length === 0) {
       return currNode;
     }
@@ -279,10 +326,11 @@ function getMaybeNonNullInInstruction(
   instr: InstructionValue,
   context: CollectHoistablePropertyLoadsContext,
 ): PropertyPathNode | null {
-  let path = null;
+  let path: ReactiveScopeDependency | null = null;
   if (instr.kind === 'PropertyLoad') {
     path = context.temporaries.get(instr.object.identifier.id) ?? {
       identifier: instr.object.identifier,
+      reactive: instr.object.reactive,
       path: [],
     };
   } else if (instr.kind === 'Destructure') {
@@ -345,7 +393,7 @@ function collectNonNullsInBlocks(
   ) {
     const identifier = fn.params[0].identifier;
     knownNonNullIdentifiers.add(
-      context.registry.getOrCreateIdentifier(identifier),
+      context.registry.getOrCreateIdentifier(identifier, true),
     );
   }
   const nodes = new Map<
@@ -580,9 +628,11 @@ function reduceMaybeOptionalChains(
     changed = false;
 
     for (const original of optionalChainNodes) {
-      let {identifier, path: origPath} = original.fullPath;
-      let currNode: PropertyPathNode =
-        registry.getOrCreateIdentifier(identifier);
+      let {identifier, path: origPath, reactive} = original.fullPath;
+      let currNode: PropertyPathNode = registry.getOrCreateIdentifier(
+        identifier,
+        reactive,
+      );
       for (let i = 0; i < origPath.length; i++) {
         const entry = origPath[i];
         // If the base is known to be non-null, replace with a non-optional load

compiler/packages/babel-plugin-react-compiler/src/HIR/CollectOptionalChainDependencies.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '..';
 import {assertNonNull} from './CollectHoistablePropertyLoads';
 import {
@@ -283,6 +290,7 @@ function traverseOptionalBlock(
     );
     baseObject = {
       identifier: maybeTest.instructions[0].value.place.identifier,
+      reactive: maybeTest.instructions[0].value.place.reactive,
       path,
     };
     test = maybeTest.terminal;
@@ -384,6 +392,7 @@ function traverseOptionalBlock(
   );
   const load = {
     identifier: baseObject.identifier,
+    reactive: baseObject.reactive,
     path: [
       ...baseObject.path,
       {

compiler/packages/babel-plugin-react-compiler/src/HIR/DeriveMinimalDependenciesHIR.ts

@@ -25,8 +25,9 @@ export class ReactiveScopeDependencyTreeHIR {
    * `identifier.path`, or `identifier?.path` is in this map, it is safe to
    * evaluate (non-optional) PropertyLoads from.
    */
-  #hoistableObjects: Map<Identifier, HoistableNode> = new Map();
-  #deps: Map<Identifier, DependencyNode> = new Map();
+  #hoistableObjects: Map<Identifier, HoistableNode & {reactive: boolean}> =
+    new Map();
+  #deps: Map<Identifier, DependencyNode & {reactive: boolean}> = new Map();
 
   /**
    * @param hoistableObjects a set of paths from which we can safely evaluate
@@ -35,9 +36,10 @@ export class ReactiveScopeDependencyTreeHIR {
    * duplicates when traversing the CFG.
    */
   constructor(hoistableObjects: Iterable<ReactiveScopeDependency>) {
-    for (const {path, identifier} of hoistableObjects) {
+    for (const {path, identifier, reactive} of hoistableObjects) {
       let currNode = ReactiveScopeDependencyTreeHIR.#getOrCreateRoot(
         identifier,
+        reactive,
         this.#hoistableObjects,
         path.length > 0 && path[0].optional ? 'Optional' : 'NonNull',
       );
@@ -70,7 +72,8 @@ export class ReactiveScopeDependencyTreeHIR {
 
   static #getOrCreateRoot<T extends string>(
     identifier: Identifier,
-    roots: Map<Identifier, TreeNode<T>>,
+    reactive: boolean,
+    roots: Map<Identifier, TreeNode<T> & {reactive: boolean}>,
     defaultAccessType: T,
   ): TreeNode<T> {
     // roots can always be accessed unconditionally in JS
@@ -79,9 +82,16 @@ export class ReactiveScopeDependencyTreeHIR {
     if (rootNode === undefined) {
       rootNode = {
         properties: new Map(),
+        reactive,
         accessType: defaultAccessType,
       };
       roots.set(identifier, rootNode);
+    } else {
+      CompilerError.invariant(reactive === rootNode.reactive, {
+        reason: '[DeriveMinimalDependenciesHIR] Conflicting reactive root flag',
+        description: `Identifier ${printIdentifier(identifier)}`,
+        loc: GeneratedSource,
+      });
     }
     return rootNode;
   }
@@ -92,9 +102,10 @@ export class ReactiveScopeDependencyTreeHIR {
    * safe-to-evaluate subpath
    */
   addDependency(dep: ReactiveScopeDependency): void {
-    const {identifier, path} = dep;
+    const {identifier, reactive, path} = dep;
     let depCursor = ReactiveScopeDependencyTreeHIR.#getOrCreateRoot(
       identifier,
+      reactive,
       this.#deps,
       PropertyAccessType.UnconditionalAccess,
     );
@@ -172,7 +183,13 @@ export class ReactiveScopeDependencyTreeHIR {
   deriveMinimalDependencies(): Set<ReactiveScopeDependency> {
     const results = new Set<ReactiveScopeDependency>();
     for (const [rootId, rootNode] of this.#deps.entries()) {
-      collectMinimalDependenciesInSubtree(rootNode, rootId, [], results);
+      collectMinimalDependenciesInSubtree(
+        rootNode,
+        rootNode.reactive,
+        rootId,
+        [],
+        results,
+      );
     }
 
     return results;
@@ -294,25 +311,24 @@ type HoistableNode = TreeNode<'Optional' | 'NonNull'>;
 type DependencyNode = TreeNode<PropertyAccessType>;
 
 /**
- * TODO: this is directly pasted from DeriveMinimalDependencies. Since we no
- * longer have conditionally accessed nodes, we can simplify
- *
  * Recursively calculates minimal dependencies in a subtree.
  * @param node DependencyNode representing a dependency subtree.
  * @returns a minimal list of dependencies in this subtree.
  */
 function collectMinimalDependenciesInSubtree(
   node: DependencyNode,
+  reactive: boolean,
   rootIdentifier: Identifier,
   path: Array<DependencyPathEntry>,
   results: Set<ReactiveScopeDependency>,
 ): void {
   if (isDependency(node.accessType)) {
-    results.add({identifier: rootIdentifier, path});
+    results.add({identifier: rootIdentifier, reactive, path});
   } else {
     for (const [childName, childNode] of node.properties) {
       collectMinimalDependenciesInSubtree(
         childNode,
+        reactive,
         rootIdentifier,
         [
           ...path,

compiler/packages/babel-plugin-react-compiler/src/HIR/Environment.ts

@@ -9,13 +9,7 @@ import * as t from '@babel/types';
 import {ZodError, z} from 'zod';
 import {fromZodError} from 'zod-validation-error';
 import {CompilerError} from '../CompilerError';
-import {
-  CompilationMode,
-  Logger,
-  PanicThresholdOptions,
-  parsePluginOptions,
-  PluginOptions,
-} from '../Entrypoint';
+import {Logger, ProgramContext} from '../Entrypoint';
 import {Err, Ok, Result} from '../Utils/Result';
 import {
   DEFAULT_GLOBALS,
@@ -53,7 +47,7 @@ import {
   ShapeRegistry,
   addHook,
 } from './ObjectShape';
-import {Scope as BabelScope} from '@babel/traverse';
+import {Scope as BabelScope, NodePath} from '@babel/traverse';
 import {TypeSchema} from './TypeSchema';
 
 export const ReactElementSymbolSchema = z.object({
@@ -84,6 +78,8 @@ export const InstrumentationSchema = z
   );
 
 export type ExternalFunction = z.infer<typeof ExternalFunctionSchema>;
+export const USE_FIRE_FUNCTION_NAME = 'useFire';
+export const EMIT_FREEZE_GLOBAL_GATING = '__DEV__';
 
 export const MacroMethodSchema = z.union([
   z.object({type: z.literal('wildcard')}),
@@ -154,7 +150,7 @@ export type Hook = z.infer<typeof HookSchema>;
  *   missing some recursive Object / Function shapeIds
  */
 
-const EnvironmentConfigSchema = z.object({
+export const EnvironmentConfigSchema = z.object({
   customHooks: z.map(z.string(), HookSchema).default(new Map()),
 
   /**
@@ -247,6 +243,11 @@ const EnvironmentConfigSchema = z.object({
    */
   enableUseTypeAnnotations: z.boolean().default(false),
 
+  /**
+   * Enable a new model for mutability and aliasing inference
+   */
+  enableNewMutationAliasingModel: z.boolean().default(true),
+
   /**
    * Enables inference of optional dependency chains. Without this flag
    * a property chain such as `props?.items?.foo` will infer as a dep on
@@ -330,6 +331,11 @@ const EnvironmentConfigSchema = z.object({
    */
   validateNoJSXInTryStatements: z.boolean().default(false),
 
+  /**
+   * Validates against dynamically creating components during render.
+   */
+  validateStaticComponents: z.boolean().default(false),
+
   /**
    * Validates that the dependencies of all effect hooks are memoized. This helps ensure
    * that Forget does not introduce infinite renders caused by a dependency changing,
@@ -358,6 +364,11 @@ const EnvironmentConfigSchema = z.object({
    */
   validateNoImpureFunctionsInRender: z.boolean().default(false),
 
+  /**
+   * Validate against passing mutable functions to hooks
+   */
+  validateNoFreezingKnownMutableFunctions: z.boolean().default(false),
+
   /*
    * When enabled, the compiler assumes that hooks follow the Rules of React:
    * - Hooks may memoize computation based on any of their parameters, thus
@@ -626,185 +637,6 @@ const EnvironmentConfigSchema = z.object({
 
 export type EnvironmentConfig = z.infer<typeof EnvironmentConfigSchema>;
 
-/**
- * For test fixtures and playground only.
- *
- * Pragmas are straightforward to parse for boolean options (`:true` and
- * `:false`). These are 'enabled' config values for non-boolean configs (i.e.
- * what is used when parsing `:true`).
- */
-const testComplexConfigDefaults: PartialEnvironmentConfig = {
-  validateNoCapitalizedCalls: [],
-  enableChangeDetectionForDebugging: {
-    source: 'react-compiler-runtime',
-    importSpecifierName: '$structuralCheck',
-  },
-  enableEmitFreeze: {
-    source: 'react-compiler-runtime',
-    importSpecifierName: 'makeReadOnly',
-  },
-  enableEmitInstrumentForget: {
-    fn: {
-      source: 'react-compiler-runtime',
-      importSpecifierName: 'useRenderCounter',
-    },
-    gating: {
-      source: 'react-compiler-runtime',
-      importSpecifierName: 'shouldInstrument',
-    },
-    globalGating: 'DEV',
-  },
-  enableEmitHookGuards: {
-    source: 'react-compiler-runtime',
-    importSpecifierName: '$dispatcherGuard',
-  },
-  inlineJsxTransform: {
-    elementSymbol: 'react.transitional.element',
-    globalDevVar: 'DEV',
-  },
-  lowerContextAccess: {
-    source: 'react-compiler-runtime',
-    importSpecifierName: 'useContext_withSelector',
-  },
-  inferEffectDependencies: [
-    {
-      function: {
-        source: 'react',
-        importSpecifierName: 'useEffect',
-      },
-      numRequiredArgs: 1,
-    },
-    {
-      function: {
-        source: 'shared-runtime',
-        importSpecifierName: 'useSpecialEffect',
-      },
-      numRequiredArgs: 2,
-    },
-    {
-      function: {
-        source: 'useEffectWrapper',
-        importSpecifierName: 'default',
-      },
-      numRequiredArgs: 1,
-    },
-  ],
-};
-
-/**
- * For snap test fixtures and playground only.
- */
-function parseConfigPragmaEnvironmentForTest(
-  pragma: string,
-): EnvironmentConfig {
-  const maybeConfig: any = {};
-  // Get the defaults to programmatically check for boolean properties
-  const defaultConfig = EnvironmentConfigSchema.parse({});
-
-  for (const token of pragma.split(' ')) {
-    if (!token.startsWith('@')) {
-      continue;
-    }
-    const keyVal = token.slice(1);
-    let [key, val = undefined] = keyVal.split(':');
-    const isSet = val === undefined || val === 'true';
-
-    if (isSet && key in testComplexConfigDefaults) {
-      maybeConfig[key] =
-        testComplexConfigDefaults[key as keyof PartialEnvironmentConfig];
-      continue;
-    }
-
-    if (key === 'customMacros' && val) {
-      const valSplit = val.split('.');
-      if (valSplit.length > 0) {
-        const props = [];
-        for (const elt of valSplit.slice(1)) {
-          if (elt === '*') {
-            props.push({type: 'wildcard'});
-          } else if (elt.length > 0) {
-            props.push({type: 'name', name: elt});
-          }
-        }
-        maybeConfig[key] = [[valSplit[0], props]];
-      }
-      continue;
-    }
-
-    if (
-      key !== 'enableResetCacheOnSourceFileChanges' &&
-      typeof defaultConfig[key as keyof EnvironmentConfig] !== 'boolean'
-    ) {
-      // skip parsing non-boolean properties
-      continue;
-    }
-    if (val === undefined || val === 'true') {
-      maybeConfig[key] = true;
-    } else {
-      maybeConfig[key] = false;
-    }
-  }
-  const config = EnvironmentConfigSchema.safeParse(maybeConfig);
-  if (config.success) {
-    /**
-     * Unless explicitly enabled, do not insert HMR handling code
-     * in test fixtures or playground to reduce visual noise.
-     */
-    if (config.data.enableResetCacheOnSourceFileChanges == null) {
-      config.data.enableResetCacheOnSourceFileChanges = false;
-    }
-    return config.data;
-  }
-  CompilerError.invariant(false, {
-    reason: 'Internal error, could not parse config from pragma string',
-    description: `${fromZodError(config.error)}`,
-    loc: null,
-    suggestions: null,
-  });
-}
-export function parseConfigPragmaForTests(
-  pragma: string,
-  defaults: {
-    compilationMode: CompilationMode;
-  },
-): PluginOptions {
-  const environment = parseConfigPragmaEnvironmentForTest(pragma);
-  let compilationMode: CompilationMode = defaults.compilationMode;
-  let panicThreshold: PanicThresholdOptions = 'all_errors';
-  for (const token of pragma.split(' ')) {
-    if (!token.startsWith('@')) {
-      continue;
-    }
-    switch (token) {
-      case '@compilationMode(annotation)': {
-        compilationMode = 'annotation';
-        break;
-      }
-      case '@compilationMode(infer)': {
-        compilationMode = 'infer';
-        break;
-      }
-      case '@compilationMode(all)': {
-        compilationMode = 'all';
-        break;
-      }
-      case '@compilationMode(syntax)': {
-        compilationMode = 'syntax';
-        break;
-      }
-      case '@panicThreshold(none)': {
-        panicThreshold = 'none';
-        break;
-      }
-    }
-  }
-  return parsePluginOptions({
-    environment,
-    compilationMode,
-    panicThreshold,
-  });
-}
-
 export type PartialEnvironmentConfig = Partial<EnvironmentConfig>;
 
 export type ReactFunctionType = 'Component' | 'Hook' | 'Other';
@@ -841,12 +673,14 @@ export class Environment {
   config: EnvironmentConfig;
   fnType: ReactFunctionType;
   compilerMode: CompilerMode;
-  useMemoCacheIdentifier: string;
-  hasLoweredContextAccess: boolean;
+  programContext: ProgramContext;
   hasFireRewrite: boolean;
+  hasInferredEffect: boolean;
+  inferredEffectLocations: Set<SourceLocation> = new Set();
 
   #contextIdentifiers: Set<t.Identifier>;
   #hoistedIdentifiers: Set<t.Identifier>;
+  parentFunction: NodePath<t.Function>;
 
   constructor(
     scope: BabelScope,
@@ -854,10 +688,11 @@ export class Environment {
     compilerMode: CompilerMode,
     config: EnvironmentConfig,
     contextIdentifiers: Set<t.Identifier>,
+    parentFunction: NodePath<t.Function>, // the outermost function being compiled
     logger: Logger | null,
     filename: string | null,
     code: string | null,
-    useMemoCacheIdentifier: string,
+    programContext: ProgramContext,
   ) {
     this.#scope = scope;
     this.fnType = fnType;
@@ -866,11 +701,11 @@ export class Environment {
     this.filename = filename;
     this.code = code;
     this.logger = logger;
-    this.useMemoCacheIdentifier = useMemoCacheIdentifier;
+    this.programContext = programContext;
     this.#shapes = new Map(DEFAULT_SHAPES);
     this.#globals = new Map(DEFAULT_GLOBALS);
-    this.hasLoweredContextAccess = false;
     this.hasFireRewrite = false;
+    this.hasInferredEffect = false;
 
     if (
       config.disableMemoizationForDebugging &&
@@ -912,6 +747,7 @@ export class Environment {
       this.#moduleTypes.set(REANIMATED_MODULE_NAME, reanimatedModuleType);
     }
 
+    this.parentFunction = parentFunction;
     this.#contextIdentifiers = contextIdentifiers;
     this.#hoistedIdentifiers = new Set();
   }
@@ -932,6 +768,23 @@ export class Environment {
     return makeScopeId(this.#nextScope++);
   }
 
+  get scope(): BabelScope {
+    return this.#scope;
+  }
+
+  logErrors(errors: Result<void, CompilerError>): void {
+    if (errors.isOk() || this.logger == null) {
+      return;
+    }
+    for (const error of errors.unwrapErr().details) {
+      this.logger.logEvent(this.filename, {
+        kind: 'CompileError',
+        detail: error,
+        fnLoc: null,
+      });
+    }
+  }
+
   isContextIdentifier(node: t.Identifier): boolean {
     return this.#contextIdentifiers.has(node);
   }

compiler/packages/babel-plugin-react-compiler/src/HIR/Globals.ts

@@ -5,14 +5,19 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {Effect, ValueKind, ValueReason} from './HIR';
+import {Effect, makeIdentifierId, ValueKind, ValueReason} from './HIR';
 import {
   BUILTIN_SHAPES,
   BuiltInArrayId,
+  BuiltInFireFunctionId,
   BuiltInFireId,
+  BuiltInMapId,
   BuiltInMixedReadonlyId,
+  BuiltInObjectId,
+  BuiltInSetId,
   BuiltInUseActionStateId,
   BuiltInUseContextHookId,
+  BuiltInUseEffectEventId,
   BuiltInUseEffectHookId,
   BuiltInUseInsertionEffectHookId,
   BuiltInUseLayoutEffectHookId,
@@ -21,10 +26,15 @@ import {
   BuiltInUseRefId,
   BuiltInUseStateId,
   BuiltInUseTransitionId,
+  BuiltInWeakMapId,
+  BuiltInWeakSetId,
+  BuiltinEffectEventId,
+  ReanimatedSharedValueId,
   ShapeRegistry,
   addFunction,
   addHook,
   addObject,
+  signatureArgument,
 } from './ObjectShape';
 import {BuiltInType, ObjectType, PolyType} from './Types';
 import {TypeConfig} from './TypeSchema';
@@ -45,29 +55,23 @@ export const DEFAULT_SHAPES: ShapeRegistry = new Map(BUILTIN_SHAPES);
 
 // Hack until we add ObjectShapes for all globals
 const UNTYPED_GLOBALS: Set<string> = new Set([
-  'String',
   'Object',
   'Function',
-  'Number',
   'RegExp',
   'Date',
   'Error',
-  'Function',
   'TypeError',
   'RangeError',
   'ReferenceError',
   'SyntaxError',
   'URIError',
   'EvalError',
-  'Boolean',
   'DataView',
   'Float32Array',
   'Float64Array',
   'Int8Array',
   'Int16Array',
   'Int32Array',
-  'Map',
-  'Set',
   'WeakMap',
   'Uint8Array',
   'Uint8ClampedArray',
@@ -75,16 +79,8 @@ const UNTYPED_GLOBALS: Set<string> = new Set([
   'Uint32Array',
   'ArrayBuffer',
   'JSON',
-  'parseFloat',
-  'parseInt',
   'console',
-  'isNaN',
   'eval',
-  'isFinite',
-  'encodeURI',
-  'decodeURI',
-  'encodeURIComponent',
-  'decodeURIComponent',
 ]);
 
 const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
@@ -101,6 +97,23 @@ const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
           returnValueKind: ValueKind.Mutable,
         }),
       ],
+      [
+        /**
+         * Object.fromEntries(iterable)
+         * iterable: An iterable, such as an Array or Map, containing a list of
+         *           objects. Each object should have two properties.
+         * Returns a new object whose properties are given by the entries of the
+         * iterable.
+         */
+        'fromEntries',
+        addFunction(DEFAULT_SHAPES, [], {
+          positionalParams: [Effect.ConditionallyMutate],
+          restParam: null,
+          returnType: {kind: 'Object', shapeId: BuiltInObjectId},
+          calleeEffect: Effect.Read,
+          returnValueKind: ValueKind.Mutable,
+        }),
+      ],
     ]),
   ],
   [
@@ -132,7 +145,7 @@ const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
         'from',
         addFunction(DEFAULT_SHAPES, [], {
           positionalParams: [
-            Effect.ConditionallyMutate,
+            Effect.ConditionallyMutateIterator,
             Effect.ConditionallyMutate,
             Effect.ConditionallyMutate,
           ],
@@ -372,6 +385,150 @@ const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
       returnValueKind: ValueKind.Primitive,
     }),
   ],
+  [
+    'parseInt',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'parseFloat',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'isNaN',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'isFinite',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'encodeURI',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'encodeURIComponent',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'decodeURI',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'decodeURIComponent',
+    addFunction(DEFAULT_SHAPES, [], {
+      positionalParams: [],
+      restParam: Effect.Read,
+      returnType: {kind: 'Primitive'},
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'Map',
+    addFunction(
+      DEFAULT_SHAPES,
+      [],
+      {
+        positionalParams: [Effect.ConditionallyMutateIterator],
+        restParam: null,
+        returnType: {kind: 'Object', shapeId: BuiltInMapId},
+        calleeEffect: Effect.Read,
+        returnValueKind: ValueKind.Mutable,
+      },
+      null,
+      true,
+    ),
+  ],
+  [
+    'Set',
+    addFunction(
+      DEFAULT_SHAPES,
+      [],
+      {
+        positionalParams: [Effect.ConditionallyMutateIterator],
+        restParam: null,
+        returnType: {kind: 'Object', shapeId: BuiltInSetId},
+        calleeEffect: Effect.Read,
+        returnValueKind: ValueKind.Mutable,
+      },
+      null,
+      true,
+    ),
+  ],
+  [
+    'WeakMap',
+    addFunction(
+      DEFAULT_SHAPES,
+      [],
+      {
+        positionalParams: [Effect.ConditionallyMutateIterator],
+        restParam: null,
+        returnType: {kind: 'Object', shapeId: BuiltInWeakMapId},
+        calleeEffect: Effect.Read,
+        returnValueKind: ValueKind.Mutable,
+      },
+      null,
+      true,
+    ),
+  ],
+  [
+    'WeakSet',
+    addFunction(
+      DEFAULT_SHAPES,
+      [],
+      {
+        positionalParams: [Effect.ConditionallyMutateIterator],
+        restParam: null,
+        returnType: {kind: 'Object', shapeId: BuiltInWeakSetId},
+        calleeEffect: Effect.Read,
+        returnValueKind: ValueKind.Mutable,
+      },
+      null,
+      true,
+    ),
+  ],
   // TODO: rest of Global objects
 ];
 
@@ -488,6 +645,41 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         calleeEffect: Effect.Read,
         hookKind: 'useEffect',
         returnValueKind: ValueKind.Frozen,
+        aliasing: {
+          receiver: makeIdentifierId(0),
+          params: [],
+          rest: makeIdentifierId(1),
+          returns: makeIdentifierId(2),
+          temporaries: [signatureArgument(3)],
+          effects: [
+            // Freezes the function and deps
+            {
+              kind: 'Freeze',
+              value: signatureArgument(1),
+              reason: ValueReason.Effect,
+            },
+            // Internally creates an effect object that captures the function and deps
+            {
+              kind: 'Create',
+              into: signatureArgument(3),
+              value: ValueKind.Frozen,
+              reason: ValueReason.KnownReturnSignature,
+            },
+            // The effect stores the function and dependencies
+            {
+              kind: 'Capture',
+              from: signatureArgument(1),
+              into: signatureArgument(3),
+            },
+            // Returns undefined
+            {
+              kind: 'Create',
+              into: signatureArgument(2),
+              value: ValueKind.Primitive,
+              reason: ValueReason.KnownReturnSignature,
+            },
+          ],
+        },
       },
       BuiltInUseEffectHookId,
     ),
@@ -556,13 +748,39 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       {
         positionalParams: [],
         restParam: null,
-        returnType: {kind: 'Primitive'},
+        returnType: {
+          kind: 'Function',
+          return: {kind: 'Poly'},
+          shapeId: BuiltInFireFunctionId,
+          isConstructor: false,
+        },
         calleeEffect: Effect.Read,
         returnValueKind: ValueKind.Frozen,
       },
       BuiltInFireId,
     ),
   ],
+  [
+    'useEffectEvent',
+    addHook(
+      DEFAULT_SHAPES,
+      {
+        positionalParams: [],
+        restParam: Effect.Freeze,
+        returnType: {
+          kind: 'Function',
+          return: {kind: 'Poly'},
+          shapeId: BuiltinEffectEventId,
+          isConstructor: false,
+        },
+        calleeEffect: Effect.Read,
+        hookKind: 'useEffectEvent',
+        // Frozen because it should not mutate any locally-bound values
+        returnValueKind: ValueKind.Frozen,
+      },
+      BuiltInUseEffectEventId,
+    ),
+  ],
 ];
 
 TYPED_GLOBALS.push(
@@ -784,7 +1002,7 @@ export function getReanimatedModuleType(registry: ShapeRegistry): ObjectType {
       addHook(registry, {
         positionalParams: [],
         restParam: Effect.Freeze,
-        returnType: {kind: 'Poly'},
+        returnType: {kind: 'Object', shapeId: ReanimatedSharedValueId},
         returnValueKind: ValueKind.Mutable,
         noAlias: true,
         calleeEffect: Effect.Read,

compiler/packages/babel-plugin-react-compiler/src/HIR/HIR.ts

@@ -10,9 +10,10 @@ import * as t from '@babel/types';
 import {CompilerError, CompilerErrorDetailOptions} from '../CompilerError';
 import {assertExhaustive} from '../Utils/utils';
 import {Environment, ReactFunctionType} from './Environment';
-import {HookKind} from './ObjectShape';
+import type {HookKind} from './ObjectShape';
 import {Type, makeType} from './Types';
 import {z} from 'zod';
+import type {AliasingEffect} from '../Inference/AliasingEffects';
 
 /*
  * *******************************************************************************************
@@ -100,6 +101,7 @@ export type ReactiveInstruction = {
   id: InstructionId;
   lvalue: Place | null;
   value: ReactiveValue;
+  effects?: Array<AliasingEffect> | null; // TODO make non-optional
   loc: SourceLocation;
 };
 
@@ -278,12 +280,14 @@ export type HIRFunction = {
   params: Array<Place | SpreadPattern>;
   returnTypeAnnotation: t.FlowType | t.TSType | null;
   returnType: Type;
+  returns: Place;
   context: Array<Place>;
   effects: Array<FunctionEffect> | null;
   body: HIR;
   generator: boolean;
   async: boolean;
   directives: Array<string>;
+  aliasingEffects?: Array<AliasingEffect> | null;
 };
 
 export type FunctionEffect =
@@ -449,6 +453,7 @@ export type ReturnTerminal = {
   value: Place;
   id: InstructionId;
   fallthrough?: never;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type GotoTerminal = {
@@ -609,6 +614,7 @@ export type MaybeThrowTerminal = {
   id: InstructionId;
   loc: SourceLocation;
   fallthrough?: never;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type ReactiveScopeTerminal = {
@@ -645,12 +651,14 @@ export type Instruction = {
   lvalue: Place;
   value: InstructionValue;
   loc: SourceLocation;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type TInstruction<T extends InstructionValue> = {
   id: InstructionId;
   lvalue: Place;
   value: T;
+  effects: Array<AliasingEffect> | null;
   loc: SourceLocation;
 };
 
@@ -746,6 +754,27 @@ export enum InstructionKind {
   Function = 'Function',
 }
 
+export function convertHoistedLValueKind(
+  kind: InstructionKind,
+): InstructionKind | null {
+  switch (kind) {
+    case InstructionKind.HoistedLet:
+      return InstructionKind.Let;
+    case InstructionKind.HoistedConst:
+      return InstructionKind.Const;
+    case InstructionKind.HoistedFunction:
+      return InstructionKind.Function;
+    case InstructionKind.Let:
+    case InstructionKind.Const:
+    case InstructionKind.Function:
+    case InstructionKind.Reassign:
+    case InstructionKind.Catch:
+      return null;
+    default:
+      assertExhaustive(kind, 'Unexpected lvalue kind');
+  }
+}
+
 function _staticInvariantInstructionValueHasLocation(
   value: InstructionValue,
 ): SourceLocation {
@@ -829,6 +858,13 @@ export type CallExpression = {
   typeArguments?: Array<t.FlowType>;
 };
 
+export type NewExpression = {
+  kind: 'NewExpression';
+  callee: Place;
+  args: Array<Place | SpreadPattern>;
+  loc: SourceLocation;
+};
+
 export type LoadLocal = {
   kind: 'LoadLocal';
   place: Place;
@@ -873,8 +909,20 @@ export type InstructionValue =
   | StoreLocal
   | {
       kind: 'StoreContext';
+      /**
+       * StoreContext kinds:
+       * Reassign: context variable reassignment in source
+       * Const:    const declaration + assignment in source
+       *           ('const' context vars are ones whose declarations are hoisted)
+       * Let:      let declaration + assignment in source
+       * Function: function declaration in source (similar to `const`)
+       */
       lvalue: {
-        kind: InstructionKind.Reassign;
+        kind:
+          | InstructionKind.Reassign
+          | InstructionKind.Const
+          | InstructionKind.Let
+          | InstructionKind.Function;
         place: Place;
       };
       value: Place;
@@ -894,12 +942,7 @@ export type InstructionValue =
       right: Place;
       loc: SourceLocation;
     }
-  | {
-      kind: 'NewExpression';
-      callee: Place;
-      args: Array<Place | SpreadPattern>;
-      loc: SourceLocation;
-    }
+  | NewExpression
   | CallExpression
   | MethodCall
   | {
@@ -908,13 +951,21 @@ export type InstructionValue =
       value: Place;
       loc: SourceLocation;
     }
-  | {
+  | ({
       kind: 'TypeCastExpression';
       value: Place;
-      typeAnnotation: t.FlowType | t.TSType;
       type: Type;
       loc: SourceLocation;
-    }
+    } & (
+      | {
+          typeAnnotation: t.FlowType;
+          typeAnnotationKind: 'cast';
+        }
+      | {
+          typeAnnotation: t.TSType;
+          typeAnnotationKind: 'as' | 'satisfies';
+        }
+    ))
   | JsxExpression
   | {
       kind: 'ObjectExpression';
@@ -1165,18 +1216,21 @@ export type VariableBinding =
   // bindings declard outside the current component/hook
   | NonLocalBinding;
 
+// `import {bar as baz} from 'foo'`: name=baz, module=foo, imported=bar
+export type NonLocalImportSpecifier = {
+  kind: 'ImportSpecifier';
+  name: string;
+  module: string;
+  imported: string;
+};
+
 export type NonLocalBinding =
   // `import Foo from 'foo'`: name=Foo, module=foo
   | {kind: 'ImportDefault'; name: string; module: string}
   // `import * as Foo from 'foo'`: name=Foo, module=foo
   | {kind: 'ImportNamespace'; name: string; module: string}
-  // `import {bar as baz} from 'foo'`: name=baz, module=foo, imported=bar
-  | {
-      kind: 'ImportSpecifier';
-      name: string;
-      module: string;
-      imported: string;
-    }
+  // `import {bar as baz} from 'foo'`
+  | NonLocalImportSpecifier
   // let, const, function, etc declared in the module but outside the current component/hook
   | {kind: 'ModuleLocal'; name: string}
   // an unresolved binding
@@ -1334,6 +1388,11 @@ export enum ValueReason {
    */
   JsxCaptured = 'jsx-captured',
 
+  /**
+   * Passed to an effect
+   */
+  Effect = 'effect',
+
   /**
    * Return value of a function with known frozen return value, e.g. `useState`.
    */
@@ -1394,6 +1453,7 @@ export enum Effect {
   Read = 'read',
   // This reference reads and stores the value
   Capture = 'capture',
+  ConditionallyMutateIterator = 'mutate-iterator?',
   /*
    * This reference *may* write to (mutate) the value. This covers two similar cases:
    * - The compiler is being conservative and assuming that a value *may* be mutated
@@ -1412,11 +1472,11 @@ export enum Effect {
   // This reference may alias to (mutate) the value
   Store = 'store',
 }
-
 export const EffectSchema = z.enum([
   Effect.Read,
   Effect.Mutate,
   Effect.ConditionallyMutate,
+  Effect.ConditionallyMutateIterator,
   Effect.Capture,
   Effect.Store,
   Effect.Freeze,
@@ -1430,6 +1490,7 @@ export function isMutableEffect(
     case Effect.Capture:
     case Effect.Store:
     case Effect.ConditionallyMutate:
+    case Effect.ConditionallyMutateIterator:
     case Effect.Mutate: {
       return true;
     }
@@ -1520,6 +1581,18 @@ export type DependencyPathEntry = {
 export type DependencyPath = Array<DependencyPathEntry>;
 export type ReactiveScopeDependency = {
   identifier: Identifier;
+  /**
+   * Reflects whether the base identifier is reactive. Note that some reactive
+   * objects may have non-reactive properties, but we do not currently track
+   * this.
+   *
+   * ```js
+   * // Technically, result[0] is reactive and result[1] is not.
+   * // Currently, both dependencies would be marked as reactive.
+   * const result = useState();
+   * ```
+   */
+  reactive: boolean;
   path: DependencyPath;
 };
 
@@ -1649,6 +1722,14 @@ export function isArrayType(id: Identifier): boolean {
   return id.type.kind === 'Object' && id.type.shapeId === 'BuiltInArray';
 }
 
+export function isMapType(id: Identifier): boolean {
+  return id.type.kind === 'Object' && id.type.shapeId === 'BuiltInMap';
+}
+
+export function isSetType(id: Identifier): boolean {
+  return id.type.kind === 'Object' && id.type.shapeId === 'BuiltInSet';
+}
+
 export function isPropsType(id: Identifier): boolean {
   return id.type.kind === 'Object' && id.type.shapeId === 'BuiltInProps';
 }
@@ -1669,6 +1750,18 @@ export function isRefOrRefValue(id: Identifier): boolean {
   return isUseRefType(id) || isRefValueType(id);
 }
 
+/*
+ * Returns true if the type is a Ref or a custom user type that acts like a ref when it
+ * shouldn't. For now the only other case of this is Reanimated's shared values.
+ */
+export function isRefOrRefLikeMutableType(type: Type): boolean {
+  return (
+    type.kind === 'Object' &&
+    (type.shapeId === 'BuiltInUseRefId' ||
+      type.shapeId == 'ReanimatedSharedValueId')
+  );
+}
+
 export function isSetStateType(id: Identifier): boolean {
   return id.type.kind === 'Function' && id.type.shapeId === 'BuiltInSetState';
 }
@@ -1699,6 +1792,19 @@ export function isDispatcherType(id: Identifier): boolean {
   return id.type.kind === 'Function' && id.type.shapeId === 'BuiltInDispatch';
 }
 
+export function isFireFunctionType(id: Identifier): boolean {
+  return (
+    id.type.kind === 'Function' && id.type.shapeId === 'BuiltInFireFunction'
+  );
+}
+
+export function isEffectEventFunctionType(id: Identifier): boolean {
+  return (
+    id.type.kind === 'Function' &&
+    id.type.shapeId === 'BuiltInEffectEventFunction'
+  );
+}
+
 export function isStableType(id: Identifier): boolean {
   return (
     isSetStateType(id) ||
@@ -1709,6 +1815,40 @@ export function isStableType(id: Identifier): boolean {
   );
 }
 
+export function isStableTypeContainer(id: Identifier): boolean {
+  const type_ = id.type;
+  if (type_.kind !== 'Object') {
+    return false;
+  }
+  return (
+    isUseStateType(id) || // setState
+    type_.shapeId === 'BuiltInUseActionState' || // setActionState
+    isUseReducerType(id) || // dispatcher
+    type_.shapeId === 'BuiltInUseTransition' // startTransition
+  );
+}
+
+export function evaluatesToStableTypeOrContainer(
+  env: Environment,
+  {value}: Instruction,
+): boolean {
+  if (value.kind === 'CallExpression' || value.kind === 'MethodCall') {
+    const callee =
+      value.kind === 'CallExpression' ? value.callee : value.property;
+
+    const calleeHookKind = getHookKind(env, callee.identifier);
+    switch (calleeHookKind) {
+      case 'useState':
+      case 'useReducer':
+      case 'useActionState':
+      case 'useRef':
+      case 'useTransition':
+        return true;
+    }
+  }
+  return false;
+}
+
 export function isUseEffectHookType(id: Identifier): boolean {
   return (
     id.type.kind === 'Function' && id.type.shapeId === 'BuiltInUseEffectHook'

compiler/packages/babel-plugin-react-compiler/src/HIR/HIRBuilder.ts

@@ -110,7 +110,6 @@ export default class HIRBuilder {
   #bindings: Bindings;
   #env: Environment;
   #exceptionHandlerStack: Array<BlockId> = [];
-  parentFunction: NodePath<t.Function>;
   errors: CompilerError = new CompilerError();
   /**
    * Traversal context: counts the number of `fbt` tag parents
@@ -136,16 +135,17 @@ export default class HIRBuilder {
 
   constructor(
     env: Environment,
-    parentFunction: NodePath<t.Function>, // the outermost function being compiled
-    bindings: Bindings | null = null,
-    context: Array<t.Identifier> | null = null,
+    options?: {
+      bindings?: Bindings | null;
+      context?: Array<t.Identifier>;
+      entryBlockKind?: BlockKind;
+    },
   ) {
     this.#env = env;
-    this.#bindings = bindings ?? new Map();
-    this.parentFunction = parentFunction;
-    this.#context = context ?? [];
+    this.#bindings = options?.bindings ?? new Map();
+    this.#context = options?.context ?? [];
     this.#entry = makeBlockId(env.nextBlockId);
-    this.#current = newBlock(this.#entry, 'block');
+    this.#current = newBlock(this.#entry, options?.entryBlockKind ?? 'block');
   }
 
   currentBlockKind(): BlockKind {
@@ -165,6 +165,7 @@ export default class HIRBuilder {
           handler: exceptionHandler,
           id: makeInstructionId(0),
           loc: instruction.loc,
+          effects: null,
         },
         continuationBlock,
       );
@@ -239,7 +240,7 @@ export default class HIRBuilder {
 
     // Check if the binding is from module scope
     const outerBinding =
-      this.parentFunction.scope.parent.getBinding(originalName);
+      this.#env.parentFunction.scope.parent.getBinding(originalName);
     if (babelBinding === outerBinding) {
       const path = babelBinding.path;
       if (path.isImportDefaultSpecifier()) {
@@ -293,7 +294,7 @@ export default class HIRBuilder {
     const binding = this.#resolveBabelBinding(path);
     if (binding) {
       // Check if the binding is from module scope, if so return null
-      const outerBinding = this.parentFunction.scope.parent.getBinding(
+      const outerBinding = this.#env.parentFunction.scope.parent.getBinding(
         path.node.name,
       );
       if (binding === outerBinding) {
@@ -331,6 +332,7 @@ export default class HIRBuilder {
           type: makeType(),
           loc: node.loc ?? GeneratedSource,
         };
+        this.#env.programContext.addNewReference(name);
         this.#bindings.set(name, {node, identifier});
         return identifier;
       } else if (mapping.node === node) {
@@ -375,7 +377,7 @@ export default class HIRBuilder {
   }
 
   // Terminate the current block w the given terminal, and start a new block
-  terminate(terminal: Terminal, nextBlockKind: BlockKind | null): void {
+  terminate(terminal: Terminal, nextBlockKind: BlockKind | null): BlockId {
     const {id: blockId, kind, instructions} = this.#current;
     this.#completed.set(blockId, {
       kind,
@@ -389,6 +391,7 @@ export default class HIRBuilder {
       const nextId = this.#env.nextBlockId;
       this.#current = newBlock(nextId, nextBlockKind);
     }
+    return blockId;
   }
 
   /*
@@ -745,6 +748,11 @@ function getReversePostorderedBlocks(func: HIR): HIR['blocks'] {
      * (eg bb2 then bb1), we ensure that they get reversed back to the correct order.
      */
     const block = func.blocks.get(blockId)!;
+    CompilerError.invariant(block != null, {
+      reason: '[HIRBuilder] Unexpected null block',
+      description: `expected block ${blockId} to exist`,
+      loc: GeneratedSource,
+    });
     const successors = [...eachTerminalSuccessor(block.terminal)].reverse();
     const fallthrough = terminalFallthrough(block.terminal);
 

compiler/packages/babel-plugin-react-compiler/src/HIR/MergeConsecutiveBlocks.ts

@@ -12,6 +12,7 @@ import {
   GeneratedSource,
   HIRFunction,
   Instruction,
+  Place,
 } from './HIR';
 import {markPredecessors} from './HIRBuilder';
 import {terminalFallthrough, terminalHasFallthrough} from './visitors';
@@ -80,20 +81,22 @@ export function mergeConsecutiveBlocks(fn: HIRFunction): void {
         suggestions: null,
       });
       const operand = Array.from(phi.operands.values())[0]!;
+      const lvalue: Place = {
+        kind: 'Identifier',
+        identifier: phi.place.identifier,
+        effect: Effect.ConditionallyMutate,
+        reactive: false,
+        loc: GeneratedSource,
+      };
       const instr: Instruction = {
         id: predecessor.terminal.id,
-        lvalue: {
-          kind: 'Identifier',
-          identifier: phi.place.identifier,
-          effect: Effect.ConditionallyMutate,
-          reactive: false,
-          loc: GeneratedSource,
-        },
+        lvalue: {...lvalue},
         value: {
           kind: 'LoadLocal',
           place: {...operand},
           loc: GeneratedSource,
         },
+        effects: [{kind: 'Alias', from: {...operand}, into: {...lvalue}}],
         loc: GeneratedSource,
       };
       predecessor.instructions.push(instr);

compiler/packages/babel-plugin-react-compiler/src/HIR/MergeOverlappingReactiveScopesHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {
   HIRFunction,
   InstructionId,

compiler/packages/babel-plugin-react-compiler/src/HIR/ObjectShape.ts

@@ -6,10 +6,21 @@
  */
 
 import {CompilerError} from '../CompilerError';
-import {Effect, ValueKind, ValueReason} from './HIR';
+import {AliasingSignature} from '../Inference/AliasingEffects';
+import {
+  Effect,
+  GeneratedSource,
+  makeDeclarationId,
+  makeIdentifierId,
+  makeInstructionId,
+  Place,
+  ValueKind,
+  ValueReason,
+} from './HIR';
 import {
   BuiltInType,
   FunctionType,
+  makeType,
   ObjectType,
   PolyType,
   PrimitiveType,
@@ -44,6 +55,7 @@ export function addFunction(
   properties: Iterable<[string, BuiltInType | PolyType]>,
   fn: Omit<FunctionSignature, 'hookKind'>,
   id: string | null = null,
+  isConstructor: boolean = false,
 ): FunctionType {
   const shapeId = id ?? createAnonId();
   addShape(registry, shapeId, properties, {
@@ -54,6 +66,7 @@ export function addFunction(
     kind: 'Function',
     return: fn.returnType,
     shapeId,
+    isConstructor,
   };
 }
 
@@ -73,6 +86,7 @@ export function addHook(
     kind: 'Function',
     return: fn.returnType,
     shapeId,
+    isConstructor: false,
   };
 }
 
@@ -128,6 +142,7 @@ export type HookKind =
   | 'useCallback'
   | 'useTransition'
   | 'useImperativeHandle'
+  | 'useEffectEvent'
   | 'Custom';
 
 /*
@@ -176,6 +191,9 @@ export type FunctionSignature = {
   impure?: boolean;
 
   canonicalName?: string;
+
+  aliasing?: AliasingSignature | null;
+  todo_aliasing?: AliasingSignature | null;
 };
 
 /*
@@ -198,6 +216,10 @@ export type ObjectShape = {
 export type ShapeRegistry = Map<string, ObjectShape>;
 export const BuiltInPropsId = 'BuiltInProps';
 export const BuiltInArrayId = 'BuiltInArray';
+export const BuiltInSetId = 'BuiltInSet';
+export const BuiltInMapId = 'BuiltInMap';
+export const BuiltInWeakSetId = 'BuiltInWeakSet';
+export const BuiltInWeakMapId = 'BuiltInWeakMap';
 export const BuiltInFunctionId = 'BuiltInFunction';
 export const BuiltInJsxId = 'BuiltInJsx';
 export const BuiltInObjectId = 'BuiltInObject';
@@ -218,6 +240,12 @@ export const BuiltInUseContextHookId = 'BuiltInUseContextHook';
 export const BuiltInUseTransitionId = 'BuiltInUseTransition';
 export const BuiltInStartTransitionId = 'BuiltInStartTransition';
 export const BuiltInFireId = 'BuiltInFire';
+export const BuiltInFireFunctionId = 'BuiltInFireFunction';
+export const BuiltInUseEffectEventId = 'BuiltInUseEffectEvent';
+export const BuiltinEffectEventId = 'BuiltInEffectEventFunction';
+
+// See getReanimatedModuleType() in Globals.ts — this is part of supporting Reanimated's ref-like types
+export const ReanimatedSharedValueId = 'ReanimatedSharedValueId';
 
 // ShapeRegistry with default definitions for built-ins.
 export const BUILTIN_SHAPES: ShapeRegistry = new Map();
@@ -291,6 +319,30 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       returnType: PRIMITIVE_TYPE,
       calleeEffect: Effect.Store,
       returnValueKind: ValueKind.Primitive,
+      aliasing: {
+        receiver: makeIdentifierId(0),
+        params: [],
+        rest: makeIdentifierId(1),
+        returns: makeIdentifierId(2),
+        temporaries: [],
+        effects: [
+          // Push directly mutates the array itself
+          {kind: 'Mutate', value: signatureArgument(0)},
+          // The arguments are captured into the array
+          {
+            kind: 'Capture',
+            from: signatureArgument(1),
+            into: signatureArgument(0),
+          },
+          // Returns the new length, a primitive
+          {
+            kind: 'Create',
+            into: signatureArgument(2),
+            value: ValueKind.Primitive,
+            reason: ValueReason.KnownReturnSignature,
+          },
+        ],
+      },
     }),
   ],
   [
@@ -321,6 +373,62 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       returnValueKind: ValueKind.Mutable,
       noAlias: true,
       mutableOnlyIfOperandsAreMutable: true,
+      aliasing: {
+        receiver: makeIdentifierId(0),
+        params: [makeIdentifierId(1)],
+        rest: null,
+        returns: makeIdentifierId(2),
+        temporaries: [
+          // Temporary representing captured items of the receiver
+          signatureArgument(3),
+          // Temporary representing the result of the callback
+          signatureArgument(4),
+          /*
+           * Undefined `this` arg to the callback. Note the signature does not
+           * support passing an explicit thisArg second param
+           */
+          signatureArgument(5),
+        ],
+        effects: [
+          // Map creates a new mutable array
+          {
+            kind: 'Create',
+            into: signatureArgument(2),
+            value: ValueKind.Mutable,
+            reason: ValueReason.KnownReturnSignature,
+          },
+          // The first arg to the callback is an item extracted from the receiver array
+          {
+            kind: 'CreateFrom',
+            from: signatureArgument(0),
+            into: signatureArgument(3),
+          },
+          // The undefined this for the callback
+          {
+            kind: 'Create',
+            into: signatureArgument(5),
+            value: ValueKind.Primitive,
+            reason: ValueReason.KnownReturnSignature,
+          },
+          // calls the callback, returning the result into a temporary
+          {
+            kind: 'Apply',
+            receiver: signatureArgument(5),
+            args: [signatureArgument(3), {kind: 'Hole'}, signatureArgument(0)],
+            function: signatureArgument(1),
+            into: signatureArgument(4),
+            signature: null,
+            mutatesFunction: false,
+            loc: GeneratedSource,
+          },
+          // captures the result of the callback into the return array
+          {
+            kind: 'Capture',
+            from: signatureArgument(4),
+            into: signatureArgument(2),
+          },
+        ],
+      },
     }),
   ],
   [
@@ -451,6 +559,434 @@ addObject(BUILTIN_SHAPES, BuiltInObjectId, [
    */
 ]);
 
+/* Built-in Set shape */
+addObject(BUILTIN_SHAPES, BuiltInSetId, [
+  [
+    /**
+     * add(value)
+     * Parameters
+     *   value: the value of the element to add to the Set object.
+     * Returns the Set object with added value.
+     */
+    'add',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInSetId},
+      calleeEffect: Effect.Store,
+      // returnValueKind is technically dependent on the ValueKind of the set itself
+      returnValueKind: ValueKind.Mutable,
+      aliasing: {
+        receiver: makeIdentifierId(0),
+        params: [],
+        rest: makeIdentifierId(1),
+        returns: makeIdentifierId(2),
+        temporaries: [],
+        effects: [
+          // Set.add returns the receiver Set
+          {
+            kind: 'Assign',
+            from: signatureArgument(0),
+            into: signatureArgument(2),
+          },
+          // Set.add mutates the set itself
+          {
+            kind: 'Mutate',
+            value: signatureArgument(0),
+          },
+          // Captures the rest params into the set
+          {
+            kind: 'Capture',
+            from: signatureArgument(1),
+            into: signatureArgument(0),
+          },
+        ],
+      },
+    }),
+  ],
+  [
+    /**
+     * clear()
+     * Parameters none
+     * Returns undefined
+     */
+    'clear',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    /**
+     * setInstance.delete(value)
+     * Returns true if value was already in Set; otherwise false.
+     */
+    'delete',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'has',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  ['size', PRIMITIVE_TYPE],
+  [
+    /**
+     * difference(other)
+     * Parameters
+     *   other: A Set object, or set-like object.
+     * Returns a new Set object containing elements in this set but not in the other set.
+     */
+    'difference',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInSetId},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    /**
+     * union(other)
+     * Parameters
+     *   other: A Set object, or set-like object.
+     * Returns a new Set object containing elements in either this set or the other set.
+     */
+    'union',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInSetId},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    /**
+     * symmetricalDifference(other)
+     * Parameters
+     *   other: A Set object, or set-like object.
+     * A new Set object containing elements which are in either this set or the other set, but not in both.
+     */
+    'symmetricalDifference',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInSetId},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    /**
+     * isSubsetOf(other)
+     * Parameters
+     *   other: A Set object, or set-like object.
+     * Returns true if all elements in this set are also in the other set, and false otherwise.
+     */
+    'isSubsetOf',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    /**
+     * isSupersetOf(other)
+     * Parameters
+     *  other: A Set object, or set-like object.
+     * Returns true if all elements in the other set are also in this set, and false otherwise.
+     */
+    'isSupersetOf',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    /**
+     * forEach(callbackFn)
+     * forEach(callbackFn, thisArg)
+     */
+    'forEach',
+    addFunction(BUILTIN_SHAPES, [], {
+      /**
+       * see Array.map explanation for why arguments are marked `ConditionallyMutate`
+       */
+      positionalParams: [],
+      restParam: Effect.ConditionallyMutate,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.ConditionallyMutate,
+      returnValueKind: ValueKind.Primitive,
+      noAlias: true,
+      mutableOnlyIfOperandsAreMutable: true,
+    }),
+  ],
+  /**
+   * Iterators
+   */
+  [
+    'entries',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    'keys',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    'values',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+]);
+addObject(BUILTIN_SHAPES, BuiltInMapId, [
+  [
+    /**
+     * clear()
+     * Parameters none
+     * Returns undefined
+     */
+    'clear',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'delete',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'get',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    'has',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    /**
+     * Params
+     *   key: the key of the element to add to the Map object. The key may be
+     *   any JavaScript type (any primitive value or any type of JavaScript
+     *   object).
+     *   value: the value of the element to add to the Map object.
+     * Returns the Map object.
+     */
+    'set',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture, Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInMapId},
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  ['size', PRIMITIVE_TYPE],
+  [
+    'forEach',
+    addFunction(BUILTIN_SHAPES, [], {
+      /**
+       * see Array.map explanation for why arguments are marked `ConditionallyMutate`
+       */
+      positionalParams: [],
+      restParam: Effect.ConditionallyMutate,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.ConditionallyMutate,
+      returnValueKind: ValueKind.Primitive,
+      noAlias: true,
+      mutableOnlyIfOperandsAreMutable: true,
+    }),
+  ],
+  /**
+   * Iterators
+   */
+  [
+    'entries',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    'keys',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    'values',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+]);
+
+addObject(BUILTIN_SHAPES, BuiltInWeakSetId, [
+  [
+    /**
+     * add(value)
+     * Parameters
+     *   value: the value of the element to add to the Set object.
+     * Returns the Set object with added value.
+     */
+    'add',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInWeakSetId},
+      calleeEffect: Effect.Store,
+      // returnValueKind is technically dependent on the ValueKind of the set itself
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    /**
+     * setInstance.delete(value)
+     * Returns true if value was already in Set; otherwise false.
+     */
+    'delete',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'has',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+]);
+
+addObject(BUILTIN_SHAPES, BuiltInWeakMapId, [
+  [
+    'delete',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    'get',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: {kind: 'Poly'},
+      calleeEffect: Effect.Capture,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+  [
+    'has',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Read],
+      restParam: null,
+      returnType: PRIMITIVE_TYPE,
+      calleeEffect: Effect.Read,
+      returnValueKind: ValueKind.Primitive,
+    }),
+  ],
+  [
+    /**
+     * Params
+     *   key: the key of the element to add to the Map object. The key may be
+     *   any JavaScript type (any primitive value or any type of JavaScript
+     *   object).
+     *   value: the value of the element to add to the Map object.
+     * Returns the Map object.
+     */
+    'set',
+    addFunction(BUILTIN_SHAPES, [], {
+      positionalParams: [Effect.Capture, Effect.Capture],
+      restParam: null,
+      returnType: {kind: 'Object', shapeId: BuiltInWeakMapId},
+      calleeEffect: Effect.Store,
+      returnValueKind: ValueKind.Mutable,
+    }),
+  ],
+]);
+
 addObject(BUILTIN_SHAPES, BuiltInUseStateId, [
   ['0', {kind: 'Poly'}],
   [
@@ -535,6 +1071,19 @@ addObject(BUILTIN_SHAPES, BuiltInRefValueId, [
   ['*', {kind: 'Object', shapeId: BuiltInRefValueId}],
 ]);
 
+addFunction(
+  BUILTIN_SHAPES,
+  [],
+  {
+    positionalParams: [],
+    restParam: Effect.ConditionallyMutate,
+    returnType: {kind: 'Poly'},
+    calleeEffect: Effect.ConditionallyMutate,
+    returnValueKind: ValueKind.Mutable,
+  },
+  BuiltinEffectEventId,
+);
+
 /**
  * MixedReadOnly =
  *   | primitive
@@ -756,3 +1305,22 @@ export const DefaultNonmutatingHook = addHook(
   },
   'DefaultNonmutatingHook',
 );
+
+export function signatureArgument(id: number): Place {
+  const place: Place = {
+    kind: 'Identifier',
+    effect: Effect.Unknown,
+    loc: GeneratedSource,
+    reactive: false,
+    identifier: {
+      declarationId: makeDeclarationId(id),
+      id: makeIdentifierId(id),
+      loc: GeneratedSource,
+      mutableRange: {start: makeInstructionId(0), end: makeInstructionId(0)},
+      name: null,
+      scope: null,
+      type: makeType(),
+    },
+  };
+  return place;
+}

compiler/packages/babel-plugin-react-compiler/src/HIR/PrintHIR.ts

@@ -35,6 +35,7 @@ import type {
   Type,
 } from './HIR';
 import {GotoVariant, InstructionKind} from './HIR';
+import {AliasingEffect, AliasingSignature} from '../Inference/AliasingEffects';
 
 export type Options = {
   indent: number;
@@ -67,13 +68,15 @@ export function printFunction(fn: HIRFunction): string {
         })
         .join(', ') +
       ')';
+  } else {
+    definition += '()';
   }
   if (definition.length !== 0) {
     output.push(definition);
   }
-  output.push(printType(fn.returnType));
-  output.push(printHIR(fn.body));
+  output.push(`: ${printType(fn.returnType)} @ ${printPlace(fn.returns)}`);
   output.push(...fn.directives);
+  output.push(printHIR(fn.body));
   return output.join('\n');
 }
 
@@ -151,7 +154,10 @@ export function printMixedHIR(
 
 export function printInstruction(instr: ReactiveInstruction): string {
   const id = `[${instr.id}]`;
-  const value = printInstructionValue(instr.value);
+  let value = printInstructionValue(instr.value);
+  if (instr.effects != null) {
+    value += `\n    ${instr.effects.map(printAliasingEffect).join('\n    ')}`;
+  }
 
   if (instr.lvalue !== null) {
     return `${id} ${printPlace(instr.lvalue)} = ${value}`;
@@ -213,6 +219,9 @@ export function printTerminal(terminal: Terminal): Array<string> | string {
       value = `[${terminal.id}] Return${
         terminal.value != null ? ' ' + printPlace(terminal.value) : ''
       }`;
+      if (terminal.effects != null) {
+        value += `\n    ${terminal.effects.map(printAliasingEffect).join('\n    ')}`;
+      }
       break;
     }
     case 'goto': {
@@ -281,6 +290,9 @@ export function printTerminal(terminal: Terminal): Array<string> | string {
     }
     case 'maybe-throw': {
       value = `[${terminal.id}] MaybeThrow continuation=bb${terminal.continuation} handler=bb${terminal.handler}`;
+      if (terminal.effects != null) {
+        value += `\n    ${terminal.effects.map(printAliasingEffect).join('\n    ')}`;
+      }
       break;
     }
     case 'scope': {
@@ -555,8 +567,11 @@ export function printInstructionValue(instrValue: ReactiveValue): string {
             }
           })
           .join(', ') ?? '';
-      const type = printType(instrValue.loweredFunc.func.returnType).trim();
-      value = `${kind} ${name} @context[${context}] @effects[${effects}]${type !== '' ? ` return${type}` : ''}:\n${fn}`;
+      const aliasingEffects =
+        instrValue.loweredFunc.func.aliasingEffects
+          ?.map(printAliasingEffect)
+          ?.join(', ') ?? '';
+      value = `${kind} ${name} @context[${context}] @effects[${effects}] @aliasingEffects=[${aliasingEffects}]\n${fn}`;
       break;
     }
     case 'TaggedTemplateExpression': {
@@ -922,3 +937,107 @@ function getFunctionName(
       return defaultValue;
   }
 }
+
+export function printAliasingEffect(effect: AliasingEffect): string {
+  switch (effect.kind) {
+    case 'Assign': {
+      return `Assign ${printPlaceForAliasEffect(effect.into)} = ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'Alias': {
+      return `Alias ${printPlaceForAliasEffect(effect.into)} = ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'Capture': {
+      return `Capture ${printPlaceForAliasEffect(effect.into)} <- ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'ImmutableCapture': {
+      return `ImmutableCapture ${printPlaceForAliasEffect(effect.into)} <- ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'Create': {
+      return `Create ${printPlaceForAliasEffect(effect.into)} = ${effect.value}`;
+    }
+    case 'CreateFrom': {
+      return `Create ${printPlaceForAliasEffect(effect.into)} = kindOf(${printPlaceForAliasEffect(effect.from)})`;
+    }
+    case 'CreateFunction': {
+      return `Function ${printPlaceForAliasEffect(effect.into)} = Function captures=[${effect.captures.map(printPlaceForAliasEffect).join(', ')}]`;
+    }
+    case 'Apply': {
+      const receiverCallee =
+        effect.receiver.identifier.id === effect.function.identifier.id
+          ? printPlaceForAliasEffect(effect.receiver)
+          : `${printPlaceForAliasEffect(effect.receiver)}.${printPlaceForAliasEffect(effect.function)}`;
+      const args = effect.args
+        .map(arg => {
+          if (arg.kind === 'Identifier') {
+            return printPlaceForAliasEffect(arg);
+          } else if (arg.kind === 'Hole') {
+            return ' ';
+          }
+          return `...${printPlaceForAliasEffect(arg.place)}`;
+        })
+        .join(', ');
+      let signature = '';
+      if (effect.signature != null) {
+        if (effect.signature.aliasing != null) {
+          signature = printAliasingSignature(effect.signature.aliasing);
+        } else {
+          signature = JSON.stringify(effect.signature, null, 2);
+        }
+      }
+      return `Apply ${printPlaceForAliasEffect(effect.into)} = ${receiverCallee}(${args})${signature != '' ? '\n     ' : ''}${signature}`;
+    }
+    case 'Freeze': {
+      return `Freeze ${printPlaceForAliasEffect(effect.value)} ${effect.reason}`;
+    }
+    case 'Mutate':
+    case 'MutateConditionally':
+    case 'MutateTransitive':
+    case 'MutateTransitiveConditionally': {
+      return `${effect.kind} ${printPlaceForAliasEffect(effect.value)}`;
+    }
+    case 'MutateFrozen': {
+      return `MutateFrozen ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+    }
+    case 'MutateGlobal': {
+      return `MutateGlobal ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+    }
+    case 'Impure': {
+      return `Impure ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+    }
+    case 'Render': {
+      return `Render ${printPlaceForAliasEffect(effect.place)}`;
+    }
+    default: {
+      assertExhaustive(effect, `Unexpected kind '${(effect as any).kind}'`);
+    }
+  }
+}
+
+function printPlaceForAliasEffect(place: Place): string {
+  return printIdentifier(place.identifier);
+}
+
+export function printAliasingSignature(signature: AliasingSignature): string {
+  const tokens: Array<string> = ['function '];
+  if (signature.temporaries.length !== 0) {
+    tokens.push('<');
+    tokens.push(
+      signature.temporaries.map(temp => `$${temp.identifier.id}`).join(', '),
+    );
+    tokens.push('>');
+  }
+  tokens.push('(');
+  tokens.push('this=$' + String(signature.receiver));
+  for (const param of signature.params) {
+    tokens.push(', $' + String(param));
+  }
+  if (signature.rest != null) {
+    tokens.push(`, ...$${String(signature.rest)}`);
+  }
+  tokens.push('): ');
+  tokens.push('$' + String(signature.returns) + ':');
+  for (const effect of signature.effects) {
+    tokens.push('\n  ' + printAliasingEffect(effect));
+  }
+  return tokens.join('');
+}

compiler/packages/babel-plugin-react-compiler/src/HIR/PropagateScopeDependenciesHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {
   ScopeId,
   HIRFunction,
@@ -23,6 +30,7 @@ import {
   FunctionExpression,
   ObjectMethod,
   PropertyLiteral,
+  convertHoistedLValueKind,
 } from './HIR';
 import {
   collectHoistablePropertyLoads,
@@ -109,7 +117,7 @@ export function propagateScopeDependenciesHIR(fn: HIRFunction): void {
   }
 }
 
-function findTemporariesUsedOutsideDeclaringScope(
+export function findTemporariesUsedOutsideDeclaringScope(
   fn: HIRFunction,
 ): ReadonlySet<DeclarationId> {
   /*
@@ -239,12 +247,18 @@ function isLoadContextMutable(
   id: InstructionId,
 ): instrValue is LoadContext {
   if (instrValue.kind === 'LoadContext') {
-    CompilerError.invariant(instrValue.place.identifier.scope != null, {
-      reason:
-        '[PropagateScopeDependencies] Expected all context variables to be assigned a scope',
-      loc: instrValue.loc,
-    });
-    return id >= instrValue.place.identifier.scope.range.end;
+    /**
+     * Not all context variables currently have scopes due to limitations of
+     * mutability analysis for function expressions.
+     *
+     * Currently, many function expressions references are inferred to be
+     * 'Read' | 'Freeze' effects which don't replay mutable effects of captured
+     * context.
+     */
+    return (
+      instrValue.place.identifier.scope != null &&
+      id >= instrValue.place.identifier.scope.range.end
+    );
   }
   return false;
 }
@@ -302,6 +316,7 @@ function collectTemporariesSidemapImpl(
         ) {
           temporaries.set(lvalue.identifier.id, {
             identifier: value.place.identifier,
+            reactive: value.place.reactive,
             path: [],
           });
         }
@@ -355,11 +370,13 @@ function getProperty(
   if (resolvedDependency == null) {
     property = {
       identifier: object.identifier,
+      reactive: object.reactive,
       path: [{property: propertyName, optional}],
     };
   } else {
     property = {
       identifier: resolvedDependency.identifier,
+      reactive: resolvedDependency.reactive,
       path: [...resolvedDependency.path, {property: propertyName, optional}],
     };
   }
@@ -371,7 +388,7 @@ type Decl = {
   scope: Stack<ReactiveScope>;
 };
 
-class Context {
+export class DependencyCollectionContext {
   #declarations: Map<DeclarationId, Decl> = new Map();
   #reassignments: Map<Identifier, Decl> = new Map();
 
@@ -464,6 +481,9 @@ class Context {
     }
     this.#reassignments.set(identifier, decl);
   }
+  hasDeclared(identifier: Identifier): boolean {
+    return this.#declarations.has(identifier.declarationId);
+  }
 
   // Checks if identifier is a valid dependency in the current scope
   #checkValidDependency(maybeDependency: ReactiveScopeDependency): boolean {
@@ -515,6 +535,7 @@ class Context {
     this.visitDependency(
       this.#temporaries.get(place.identifier.id) ?? {
         identifier: place.identifier,
+        reactive: place.reactive,
         path: [],
       },
     );
@@ -579,6 +600,7 @@ class Context {
     ) {
       maybeDependency = {
         identifier: maybeDependency.identifier,
+        reactive: maybeDependency.reactive,
         path: [],
       };
     }
@@ -600,7 +622,11 @@ class Context {
         identifier =>
           identifier.declarationId === place.identifier.declarationId,
       ) &&
-      this.#checkValidDependency({identifier: place.identifier, path: []})
+      this.#checkValidDependency({
+        identifier: place.identifier,
+        reactive: place.reactive,
+        path: [],
+      })
     ) {
       currentScope.reassignments.add(place.identifier);
     }
@@ -638,7 +664,10 @@ enum HIRValue {
   Terminal,
 }
 
-function handleInstruction(instr: Instruction, context: Context): void {
+export function handleInstruction(
+  instr: Instruction,
+  context: DependencyCollectionContext,
+): void {
   const {id, value, lvalue} = instr;
   context.declare(lvalue.identifier, {
     id,
@@ -662,21 +691,21 @@ function handleInstruction(instr: Instruction, context: Context): void {
     });
   } else if (value.kind === 'DeclareLocal' || value.kind === 'DeclareContext') {
     /*
-     * Some variables may be declared and never initialized. We need
-     * to retain (and hoist) these declarations if they are included
-     * in a reactive scope. One approach is to simply add all `DeclareLocal`s
-     * as scope declarations.
+     * Some variables may be declared and never initialized. We need to retain
+     * (and hoist) these declarations if they are included in a reactive scope.
+     * One approach is to simply add all `DeclareLocal`s as scope declarations.
+     *
+     * Context variables with hoisted declarations only become live after their
+     * first assignment. We only declare real DeclareLocal / DeclareContext
+     * instructions (not hoisted ones) to avoid generating dependencies on
+     * hoisted declarations.
      */
-
-    /*
-     * We add context variable declarations here, not at `StoreContext`, since
-     * context Store / Loads are modeled as reads and mutates to the underlying
-     * variable reference (instead of through intermediate / inlined temporaries)
-     */
-    context.declare(value.lvalue.place.identifier, {
-      id,
-      scope: context.currentScope,
-    });
+    if (convertHoistedLValueKind(value.lvalue.kind) === null) {
+      context.declare(value.lvalue.place.identifier, {
+        id,
+        scope: context.currentScope,
+      });
+    }
   } else if (value.kind === 'Destructure') {
     context.visitOperand(value.value);
     for (const place of eachPatternOperand(value.lvalue.pattern)) {
@@ -688,6 +717,26 @@ function handleInstruction(instr: Instruction, context: Context): void {
         scope: context.currentScope,
       });
     }
+  } else if (value.kind === 'StoreContext') {
+    /**
+     * Some StoreContext variables have hoisted declarations. If we're storing
+     * to a context variable that hasn't yet been declared, the StoreContext is
+     * the declaration.
+     * (see corresponding logic in PruneHoistedContext)
+     */
+    if (
+      !context.hasDeclared(value.lvalue.place.identifier) ||
+      value.lvalue.kind !== InstructionKind.Reassign
+    ) {
+      context.declare(value.lvalue.place.identifier, {
+        id,
+        scope: context.currentScope,
+      });
+    }
+
+    for (const operand of eachInstructionValueOperand(value)) {
+      context.visitOperand(operand);
+    }
   } else {
     for (const operand of eachInstructionValueOperand(value)) {
       context.visitOperand(operand);
@@ -701,7 +750,7 @@ function collectDependencies(
   temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>,
   processedInstrsInOptional: ReadonlySet<Instruction | Terminal>,
 ): Map<ReactiveScope, Array<ReactiveScopeDependency>> {
-  const context = new Context(
+  const context = new DependencyCollectionContext(
     usedOutsideDeclaringScope,
     temporaries,
     processedInstrsInOptional,

compiler/packages/babel-plugin-react-compiler/src/HIR/PruneUnusedLabelsHIR.ts

@@ -1,3 +1,10 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import {CompilerError} from '..';
 import {BlockId, GotoVariant, HIRFunction} from './HIR';
 

compiler/packages/babel-plugin-react-compiler/src/HIR/ScopeDependencyUtils.ts

@@ -0,0 +1,285 @@
+import {
+  Place,
+  ReactiveScopeDependency,
+  Identifier,
+  makeInstructionId,
+  InstructionKind,
+  GeneratedSource,
+  BlockId,
+  makeTemporaryIdentifier,
+  Effect,
+  GotoVariant,
+  HIR,
+} from './HIR';
+import {CompilerError} from '../CompilerError';
+import {Environment} from './Environment';
+import HIRBuilder from './HIRBuilder';
+import {lowerValueToTemporary} from './BuildHIR';
+
+type DependencyInstructions = {
+  place: Place;
+  value: HIR;
+  exitBlockId: BlockId;
+};
+
+export function buildDependencyInstructions(
+  dep: ReactiveScopeDependency,
+  env: Environment,
+): DependencyInstructions {
+  const builder = new HIRBuilder(env, {
+    entryBlockKind: 'value',
+  });
+  let dependencyValue: Identifier;
+  if (dep.path.every(path => !path.optional)) {
+    dependencyValue = writeNonOptionalDependency(dep, env, builder);
+  } else {
+    dependencyValue = writeOptionalDependency(dep, builder, null);
+  }
+
+  const exitBlockId = builder.terminate(
+    {
+      kind: 'unsupported',
+      loc: GeneratedSource,
+      id: makeInstructionId(0),
+    },
+    null,
+  );
+  return {
+    place: {
+      kind: 'Identifier',
+      identifier: dependencyValue,
+      effect: Effect.Freeze,
+      reactive: dep.reactive,
+      loc: GeneratedSource,
+    },
+    value: builder.build(),
+    exitBlockId,
+  };
+}
+
+/**
+ * Write instructions for a simple dependency (without optional chains)
+ */
+function writeNonOptionalDependency(
+  dep: ReactiveScopeDependency,
+  env: Environment,
+  builder: HIRBuilder,
+): Identifier {
+  const loc = dep.identifier.loc;
+  let curr: Identifier = makeTemporaryIdentifier(env.nextIdentifierId, loc);
+  builder.push({
+    lvalue: {
+      identifier: curr,
+      kind: 'Identifier',
+      effect: Effect.Mutate,
+      reactive: dep.reactive,
+      loc,
+    },
+    value: {
+      kind: 'LoadLocal',
+      place: {
+        identifier: dep.identifier,
+        kind: 'Identifier',
+        effect: Effect.Freeze,
+        reactive: dep.reactive,
+        loc,
+      },
+      loc,
+    },
+    id: makeInstructionId(1),
+    loc: loc,
+    effects: null,
+  });
+
+  /**
+   * Iteratively build up dependency instructions by reading from the last written
+   * instruction.
+   */
+  for (const path of dep.path) {
+    const next = makeTemporaryIdentifier(env.nextIdentifierId, loc);
+    builder.push({
+      lvalue: {
+        identifier: next,
+        kind: 'Identifier',
+        effect: Effect.Mutate,
+        reactive: dep.reactive,
+        loc,
+      },
+      value: {
+        kind: 'PropertyLoad',
+        object: {
+          identifier: curr,
+          kind: 'Identifier',
+          effect: Effect.Freeze,
+          reactive: dep.reactive,
+          loc,
+        },
+        property: path.property,
+        loc,
+      },
+      id: makeInstructionId(1),
+      loc: loc,
+      effects: null,
+    });
+    curr = next;
+  }
+  return curr;
+}
+
+/**
+ * Write a dependency into optional blocks.
+ *
+ * e.g. `a.b?.c.d` is written to an optional block that tests `a.b` and
+ * conditionally evaluates `c.d`.
+ */
+function writeOptionalDependency(
+  dep: ReactiveScopeDependency,
+  builder: HIRBuilder,
+  parentAlternate: BlockId | null,
+): Identifier {
+  const env = builder.environment;
+  /**
+   * Reserve an identifier which will be used to store the result of this
+   * dependency.
+   */
+  const dependencyValue: Place = {
+    kind: 'Identifier',
+    identifier: makeTemporaryIdentifier(env.nextIdentifierId, GeneratedSource),
+    effect: Effect.Mutate,
+    reactive: dep.reactive,
+    loc: GeneratedSource,
+  };
+
+  /**
+   * Reserve a block which is the fallthrough (and transitive successor) of this
+   * optional chain.
+   */
+  const continuationBlock = builder.reserve(builder.currentBlockKind());
+  let alternate;
+  if (parentAlternate != null) {
+    alternate = parentAlternate;
+  } else {
+    /**
+     * If an outermost alternate block has not been reserved, write one
+     *
+     * $N = Primitive undefined
+     * $M = StoreLocal $OptionalResult = $N
+     * goto fallthrough
+     */
+    alternate = builder.enter('value', () => {
+      const temp = lowerValueToTemporary(builder, {
+        kind: 'Primitive',
+        value: undefined,
+        loc: GeneratedSource,
+      });
+      lowerValueToTemporary(builder, {
+        kind: 'StoreLocal',
+        lvalue: {kind: InstructionKind.Const, place: {...dependencyValue}},
+        value: {...temp},
+        type: null,
+        loc: GeneratedSource,
+      });
+      return {
+        kind: 'goto',
+        variant: GotoVariant.Break,
+        block: continuationBlock.id,
+        id: makeInstructionId(0),
+        loc: GeneratedSource,
+      };
+    });
+  }
+
+  // Reserve the consequent block, which is the successor of the test block
+  const consequent = builder.reserve('value');
+
+  let testIdentifier: Identifier | null = null;
+  const testBlock = builder.enter('value', () => {
+    const testDependency = {
+      ...dep,
+      path: dep.path.slice(0, dep.path.length - 1),
+    };
+    const firstOptional = dep.path.findIndex(path => path.optional);
+    CompilerError.invariant(firstOptional !== -1, {
+      reason:
+        '[ScopeDependencyUtils] Internal invariant broken: expected optional path',
+      loc: dep.identifier.loc,
+      description: null,
+      suggestions: null,
+    });
+    if (firstOptional === dep.path.length - 1) {
+      // Base case: the test block is simple
+      testIdentifier = writeNonOptionalDependency(testDependency, env, builder);
+    } else {
+      // Otherwise, the test block is a nested optional chain
+      testIdentifier = writeOptionalDependency(
+        testDependency,
+        builder,
+        alternate,
+      );
+    }
+
+    return {
+      kind: 'branch',
+      test: {
+        identifier: testIdentifier,
+        effect: Effect.Freeze,
+        kind: 'Identifier',
+        loc: GeneratedSource,
+        reactive: dep.reactive,
+      },
+      consequent: consequent.id,
+      alternate,
+      id: makeInstructionId(0),
+      loc: GeneratedSource,
+      fallthrough: continuationBlock.id,
+    };
+  });
+
+  builder.enterReserved(consequent, () => {
+    CompilerError.invariant(testIdentifier !== null, {
+      reason: 'Satisfy type checker',
+      description: null,
+      loc: null,
+      suggestions: null,
+    });
+
+    lowerValueToTemporary(builder, {
+      kind: 'StoreLocal',
+      lvalue: {kind: InstructionKind.Const, place: {...dependencyValue}},
+      value: lowerValueToTemporary(builder, {
+        kind: 'PropertyLoad',
+        object: {
+          identifier: testIdentifier,
+          kind: 'Identifier',
+          effect: Effect.Freeze,
+          reactive: dep.reactive,
+          loc: GeneratedSource,
+        },
+        property: dep.path.at(-1)!.property,
+        loc: GeneratedSource,
+      }),
+      type: null,
+      loc: GeneratedSource,
+    });
+    return {
+      kind: 'goto',
+      variant: GotoVariant.Break,
+      block: continuationBlock.id,
+      id: makeInstructionId(0),
+      loc: GeneratedSource,
+    };
+  });
+  builder.terminateWithContinuation(
+    {
+      kind: 'optional',
+      optional: dep.path.at(-1)!.optional,
+      test: testBlock,
+      fallthrough: continuationBlock.id,
+      id: makeInstructionId(0),
+      loc: GeneratedSource,
+    },
+    continuationBlock,
+  );
+
+  return dependencyValue.identifier;
+}

compiler/packages/babel-plugin-react-compiler/src/HIR/Types.ts

@@ -38,6 +38,7 @@ export type FunctionType = {
   kind: 'Function';
   shapeId: string | null;
   return: Type;
+  isConstructor: boolean;
 };
 
 export type ObjectType = {
@@ -111,6 +112,7 @@ export function duplicateType(type: Type): Type {
         kind: 'Function',
         return: duplicateType(type.return),
         shapeId: type.shapeId,
+        isConstructor: type.isConstructor,
       };
     }
     case 'Object': {

compiler/packages/babel-plugin-react-compiler/src/HIR/index.ts

@@ -17,7 +17,6 @@ export {buildReactiveScopeTerminalsHIR} from './BuildReactiveScopeTerminalsHIR';
 export {computeDominatorTree, computePostDominatorTree} from './Dominator';
 export {
   Environment,
-  parseConfigPragmaForTests,
   validateEnvironmentConfig,
   type EnvironmentConfig,
   type ExternalFunction,
@@ -32,5 +31,5 @@ export {
 } from './HIRBuilder';
 export {mergeConsecutiveBlocks} from './MergeConsecutiveBlocks';
 export {mergeOverlappingReactiveScopesHIR} from './MergeOverlappingReactiveScopesHIR';
-export {printFunction, printHIR} from './PrintHIR';
+export {printFunction, printHIR, printFunctionWithOutlined} from './PrintHIR';
 export {pruneUnusedLabelsHIR} from './PruneUnusedLabelsHIR';

compiler/packages/babel-plugin-react-compiler/src/HIR/visitors.ts

@@ -735,6 +735,7 @@ export function mapTerminalSuccessors(
         loc: terminal.loc,
         value: terminal.value,
         id: makeInstructionId(0),
+        effects: terminal.effects,
       };
     }
     case 'throw': {
@@ -842,6 +843,7 @@ export function mapTerminalSuccessors(
         handler,
         id: makeInstructionId(0),
         loc: terminal.loc,
+        effects: terminal.effects,
       };
     }
     case 'try': {

compiler/packages/babel-plugin-react-compiler/src/Inference/AliasingEffects.ts

@@ -0,0 +1,233 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {CompilerErrorDetailOptions} from '../CompilerError';
+import {
+  FunctionExpression,
+  Hole,
+  IdentifierId,
+  ObjectMethod,
+  Place,
+  SourceLocation,
+  SpreadPattern,
+  ValueKind,
+  ValueReason,
+} from '../HIR';
+import {FunctionSignature} from '../HIR/ObjectShape';
+
+/**
+ * `AliasingEffect` describes a set of "effects" that an instruction/terminal has on one or
+ * more values in a program. These effects include mutation of values, freezing values,
+ * tracking data flow between values, and other specialized cases.
+ */
+export type AliasingEffect =
+  /**
+   * Marks the given value and its direct aliases as frozen.
+   *
+   * Captured values are *not* considered frozen, because we cannot be sure that a previously
+   * captured value will still be captured at the point of the freeze.
+   *
+   * For example:
+   * const x = {};
+   * const y = [x];
+   * y.pop(); // y dosn't contain x anymore!
+   * freeze(y);
+   * mutate(x); // safe to mutate!
+   *
+   * The exception to this is FunctionExpressions - since it is impossible to change which
+   * value a function closes over[1] we can transitively freeze functions and their captures.
+   *
+   * [1] Except for `let` values that are reassigned and closed over by a function, but we
+   * handle this explicitly with StoreContext/LoadContext.
+   */
+  | {kind: 'Freeze'; value: Place; reason: ValueReason}
+  /**
+   * Mutate the value and any direct aliases (not captures). Errors if the value is not mutable.
+   */
+  | {kind: 'Mutate'; value: Place}
+  /**
+   * Mutate the value and any direct aliases (not captures), but only if the value is known mutable.
+   * This should be rare.
+   *
+   * TODO: this is only used for IteratorNext, but even then MutateTransitiveConditionally is more
+   * correct for iterators of unknown types.
+   */
+  | {kind: 'MutateConditionally'; value: Place}
+  /**
+   * Mutate the value, any direct aliases, and any transitive captures. Errors if the value is not mutable.
+   */
+  | {kind: 'MutateTransitive'; value: Place}
+  /**
+   * Mutates any of the value, its direct aliases, and its transitive captures that are mutable.
+   */
+  | {kind: 'MutateTransitiveConditionally'; value: Place}
+  /**
+   * Records information flow from `from` to `into` in cases where local mutation of the destination
+   * will *not* mutate the source:
+   *
+   * - Capture a -> b and Mutate(b) X=> (does not imply) Mutate(a)
+   * - Capture a -> b and MutateTransitive(b) => (does imply) Mutate(a)
+   *
+   * Example: `array.push(item)`. Information from item is captured into array, but there is not a
+   * direct aliasing, and local mutations of array will not modify item.
+   */
+  | {kind: 'Capture'; from: Place; into: Place}
+  /**
+   * Records information flow from `from` to `into` in cases where local mutation of the destination
+   * *will* mutate the source:
+   *
+   * - Alias a -> b and Mutate(b) => (does imply) Mutate(a)
+   * - Alias a -> b and MutateTransitive(b) => (does imply) Mutate(a)
+   *
+   * Example: `c = identity(a)`. We don't know what `identity()` returns so we can't use Assign.
+   * But we have to assume that it _could_ be returning its input, such that a local mutation of
+   * c could be mutating a.
+   */
+  | {kind: 'Alias'; from: Place; into: Place}
+  /**
+   * Records direct assignment: `into = from`.
+   */
+  | {kind: 'Assign'; from: Place; into: Place}
+  /**
+   * Creates a value of the given type at the given place
+   */
+  | {kind: 'Create'; into: Place; value: ValueKind; reason: ValueReason}
+  /**
+   * Creates a new value with the same kind as the starting value.
+   */
+  | {kind: 'CreateFrom'; from: Place; into: Place}
+  /**
+   * Immutable data flow, used for escape analysis. Does not influence mutable range analysis:
+   */
+  | {kind: 'ImmutableCapture'; from: Place; into: Place}
+  /**
+   * Calls the function at the given place with the given arguments either captured or aliased,
+   * and captures/aliases the result into the given place.
+   */
+  | {
+      kind: 'Apply';
+      receiver: Place;
+      function: Place;
+      mutatesFunction: boolean;
+      args: Array<Place | SpreadPattern | Hole>;
+      into: Place;
+      signature: FunctionSignature | null;
+      loc: SourceLocation;
+    }
+  /**
+   * Constructs a function value with the given captures. The mutability of the function
+   * will be determined by the mutability of the capture values when evaluated.
+   */
+  | {
+      kind: 'CreateFunction';
+      captures: Array<Place>;
+      function: FunctionExpression | ObjectMethod;
+      into: Place;
+    }
+  /**
+   * Mutation of a value known to be immutable
+   */
+  | {kind: 'MutateFrozen'; place: Place; error: CompilerErrorDetailOptions}
+  /**
+   * Mutation of a global
+   */
+  | {
+      kind: 'MutateGlobal';
+      place: Place;
+      error: CompilerErrorDetailOptions;
+    }
+  /**
+   * Indicates a side-effect that is not safe during render
+   */
+  | {kind: 'Impure'; place: Place; error: CompilerErrorDetailOptions}
+  /**
+   * Indicates that a given place is accessed during render. Used to distingush
+   * hook arguments that are known to be called immediately vs those used for
+   * event handlers/effects, and for JSX values known to be called during render
+   * (tags, children) vs those that may be events/effect (other props).
+   */
+  | {
+      kind: 'Render';
+      place: Place;
+    };
+
+export function hashEffect(effect: AliasingEffect): string {
+  switch (effect.kind) {
+    case 'Apply': {
+      return [
+        effect.kind,
+        effect.receiver.identifier.id,
+        effect.function.identifier.id,
+        effect.mutatesFunction,
+        effect.args
+          .map(a => {
+            if (a.kind === 'Hole') {
+              return '';
+            } else if (a.kind === 'Identifier') {
+              return a.identifier.id;
+            } else {
+              return `...${a.place.identifier.id}`;
+            }
+          })
+          .join(','),
+        effect.into.identifier.id,
+      ].join(':');
+    }
+    case 'CreateFrom':
+    case 'ImmutableCapture':
+    case 'Assign':
+    case 'Alias':
+    case 'Capture': {
+      return [
+        effect.kind,
+        effect.from.identifier.id,
+        effect.into.identifier.id,
+      ].join(':');
+    }
+    case 'Create': {
+      return [
+        effect.kind,
+        effect.into.identifier.id,
+        effect.value,
+        effect.reason,
+      ].join(':');
+    }
+    case 'Freeze': {
+      return [effect.kind, effect.value.identifier.id, effect.reason].join(':');
+    }
+    case 'Impure':
+    case 'Render':
+    case 'MutateFrozen':
+    case 'MutateGlobal': {
+      return [effect.kind, effect.place.identifier.id].join(':');
+    }
+    case 'Mutate':
+    case 'MutateConditionally':
+    case 'MutateTransitive':
+    case 'MutateTransitiveConditionally': {
+      return [effect.kind, effect.value.identifier.id].join(':');
+    }
+    case 'CreateFunction': {
+      return [
+        effect.kind,
+        effect.into.identifier.id,
+        // return places are a unique way to identify functions themselves
+        effect.function.loweredFunc.func.returns.identifier.id,
+        effect.captures.map(p => p.identifier.id).join(','),
+      ].join(':');
+    }
+  }
+}
+
+export type AliasingSignature = {
+  receiver: IdentifierId;
+  params: Array<IdentifierId>;
+  rest: IdentifierId | null;
+  returns: IdentifierId;
+  effects: Array<AliasingEffect>;
+  temporaries: Array<Place>;
+};

compiler/packages/babel-plugin-react-compiler/src/Inference/AnalyseFunctions.ts

@@ -10,6 +10,7 @@ import {
   Effect,
   HIRFunction,
   Identifier,
+  IdentifierId,
   LoweredFunction,
   isRefOrRefValue,
   makeInstructionId,
@@ -19,6 +20,10 @@ import {inferReactiveScopeVariables} from '../ReactiveScopes';
 import {rewriteInstructionKindsBasedOnReassignment} from '../SSA';
 import {inferMutableRanges} from './InferMutableRanges';
 import inferReferenceEffects from './InferReferenceEffects';
+import {assertExhaustive} from '../Utils/utils';
+import {inferMutationAliasingEffects} from './InferMutationAliasingEffects';
+import {inferMutationAliasingFunctionEffects} from './InferMutationAliasingFunctionEffects';
+import {inferMutationAliasingRanges} from './InferMutationAliasingRanges';
 
 export default function analyseFunctions(func: HIRFunction): void {
   for (const [_, block] of func.body.blocks) {
@@ -26,15 +31,27 @@ export default function analyseFunctions(func: HIRFunction): void {
       switch (instr.value.kind) {
         case 'ObjectMethod':
         case 'FunctionExpression': {
-          lower(instr.value.loweredFunc.func);
-          infer(instr.value.loweredFunc);
+          if (!func.env.config.enableNewMutationAliasingModel) {
+            lower(instr.value.loweredFunc.func);
+            infer(instr.value.loweredFunc);
+          } else {
+            lowerWithMutationAliasing(instr.value.loweredFunc.func);
+          }
 
           /**
            * Reset mutable range for outer inferReferenceEffects
            */
           for (const operand of instr.value.loweredFunc.func.context) {
-            operand.identifier.mutableRange.start = makeInstructionId(0);
-            operand.identifier.mutableRange.end = makeInstructionId(0);
+            /**
+             * NOTE: inferReactiveScopeVariables makes identifiers in the scope
+             * point to the *same* mutableRange instance. Resetting start/end
+             * here is insufficient, because a later mutation of the range
+             * for any one identifier could affect the range for other identifiers.
+             */
+            operand.identifier.mutableRange = {
+              start: makeInstructionId(0),
+              end: makeInstructionId(0),
+            };
             operand.identifier.scope = null;
           }
           break;
@@ -44,6 +61,87 @@ export default function analyseFunctions(func: HIRFunction): void {
   }
 }
 
+function lowerWithMutationAliasing(fn: HIRFunction): void {
+  /**
+   * Phase 1: similar to lower(), but using the new mutation/aliasing inference
+   */
+  analyseFunctions(fn);
+  inferMutationAliasingEffects(fn, {isFunctionExpression: true});
+  deadCodeElimination(fn);
+  inferMutationAliasingRanges(fn, {isFunctionExpression: true});
+  rewriteInstructionKindsBasedOnReassignment(fn);
+  inferReactiveScopeVariables(fn);
+  const effects = inferMutationAliasingFunctionEffects(fn);
+  fn.env.logger?.debugLogIRs?.({
+    kind: 'hir',
+    name: 'AnalyseFunction (inner)',
+    value: fn,
+  });
+  if (effects != null) {
+    fn.aliasingEffects ??= [];
+    fn.aliasingEffects?.push(...effects);
+  }
+
+  /**
+   * Phase 2: populate the Effect of each context variable to use in inferring
+   * the outer function. For example, InferMutationAliasingEffects uses context variable
+   * effects to decide if the function may be mutable or not.
+   */
+  const capturedOrMutated = new Set<IdentifierId>();
+  for (const effect of effects ?? []) {
+    switch (effect.kind) {
+      case 'Assign':
+      case 'Alias':
+      case 'Capture':
+      case 'CreateFrom': {
+        capturedOrMutated.add(effect.from.identifier.id);
+        break;
+      }
+      case 'Apply': {
+        CompilerError.invariant(false, {
+          reason: `[AnalyzeFunctions] Expected Apply effects to be replaced with more precise effects`,
+          loc: effect.function.loc,
+        });
+      }
+      case 'Mutate':
+      case 'MutateConditionally':
+      case 'MutateTransitive':
+      case 'MutateTransitiveConditionally': {
+        capturedOrMutated.add(effect.value.identifier.id);
+        break;
+      }
+      case 'Impure':
+      case 'Render':
+      case 'MutateFrozen':
+      case 'MutateGlobal':
+      case 'CreateFunction':
+      case 'Create':
+      case 'Freeze':
+      case 'ImmutableCapture': {
+        // no-op
+        break;
+      }
+      default: {
+        assertExhaustive(
+          effect,
+          `Unexpected effect kind ${(effect as any).kind}`,
+        );
+      }
+    }
+  }
+
+  for (const operand of fn.context) {
+    if (
+      capturedOrMutated.has(operand.identifier.id) ||
+      operand.effect === Effect.Capture
+    ) {
+      operand.effect = Effect.Capture;
+    } else {
+      operand.effect = Effect.Read;
+    }
+  }
+}
+
 function lower(func: HIRFunction): void {
   analyseFunctions(func);
   inferReferenceEffects(func, {isFunctionExpression: true});

compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts

@@ -197,6 +197,7 @@ function makeManualMemoizationMarkers(
         deps: depsList,
         loc: fnExpr.loc,
       },
+      effects: null,
       loc: fnExpr.loc,
     },
     {
@@ -208,6 +209,7 @@ function makeManualMemoizationMarkers(
         decl: {...memoDecl},
         loc: fnExpr.loc,
       },
+      effects: null,
       loc: fnExpr.loc,
     },
   ];

compiler/packages/babel-plugin-react-compiler/src/Inference/InerAliasForUncalledFunctions.ts

@@ -0,0 +1,134 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {
+  Effect,
+  HIRFunction,
+  Identifier,
+  isMutableEffect,
+  isRefOrRefLikeMutableType,
+  makeInstructionId,
+} from '../HIR/HIR';
+import {eachInstructionValueOperand} from '../HIR/visitors';
+import {isMutable} from '../ReactiveScopes/InferReactiveScopeVariables';
+import DisjointSet from '../Utils/DisjointSet';
+
+/**
+ * If a function captures a mutable value but never gets called, we don't infer a
+ * mutable range for that function. This means that we also don't alias the function
+ * with its mutable captures.
+ *
+ * This case is tricky, because we don't generally know for sure what is a mutation
+ * and what may just be a normal function call. For example:
+ *
+ * ```
+ * hook useFoo() {
+ *   const x = makeObject();
+ *   return () => {
+ *     return readObject(x); // could be a mutation!
+ *   }
+ * }
+ * ```
+ *
+ * If we pessimistically assume that all such cases are mutations, we'd have to group
+ * lots of memo scopes together unnecessarily. However, if there is definitely a mutation:
+ *
+ * ```
+ * hook useFoo(createEntryForKey) {
+ *   const cache = new WeakMap();
+ *   return (key) => {
+ *     let entry = cache.get(key);
+ *     if (entry == null) {
+ *       entry = createEntryForKey(key);
+ *       cache.set(key, entry); // known mutation!
+ *     }
+ *     return entry;
+ *   }
+ * }
+ * ```
+ *
+ * Then we have to ensure that the function and its mutable captures alias together and
+ * end up in the same scope. However, aliasing together isn't enough if the function
+ * and operands all have empty mutable ranges (end = start + 1).
+ *
+ * This pass finds function expressions and object methods that have an empty mutable range
+ * and known-mutable operands which also don't have a mutable range, and ensures that the
+ * function and those operands are aliased together *and* that their ranges are updated to
+ * end after the function expression. This is sufficient to ensure that a reactive scope is
+ * created for the alias set.
+ */
+export function inferAliasForUncalledFunctions(
+  fn: HIRFunction,
+  aliases: DisjointSet<Identifier>,
+): void {
+  for (const block of fn.body.blocks.values()) {
+    instrs: for (const instr of block.instructions) {
+      const {lvalue, value} = instr;
+      if (
+        value.kind !== 'ObjectMethod' &&
+        value.kind !== 'FunctionExpression'
+      ) {
+        continue;
+      }
+      /*
+       * If the function is known to be mutated, we will have
+       * already aliased any mutable operands with it
+       */
+      const range = lvalue.identifier.mutableRange;
+      if (range.end > range.start + 1) {
+        continue;
+      }
+      /*
+       * If the function already has operands with an active mutable range,
+       * then we don't need to do anything — the function will have already
+       * been visited and included in some mutable alias set. This case can
+       * also occur due to visiting the same function in an earlier iteration
+       * of the outer fixpoint loop.
+       */
+      for (const operand of eachInstructionValueOperand(value)) {
+        if (isMutable(instr, operand)) {
+          continue instrs;
+        }
+      }
+      const operands: Set<Identifier> = new Set();
+      for (const effect of value.loweredFunc.func.effects ?? []) {
+        if (effect.kind !== 'ContextMutation') {
+          continue;
+        }
+        /*
+         * We're looking for known-mutations only, so we look at the effects
+         * rather than function context
+         */
+        if (effect.effect === Effect.Store || effect.effect === Effect.Mutate) {
+          for (const operand of effect.places) {
+            /*
+             * It's possible that function effect analysis thinks there was a context mutation,
+             * but then InferReferenceEffects figures out some operands are globals and therefore
+             * creates a non-mutable effect for those operands.
+             * We should change InferReferenceEffects to swap the ContextMutation for a global
+             * mutation in that case, but for now we just filter them out here
+             */
+            if (
+              isMutableEffect(operand.effect, operand.loc) &&
+              !isRefOrRefLikeMutableType(operand.identifier.type)
+            ) {
+              operands.add(operand.identifier);
+            }
+          }
+        }
+      }
+      if (operands.size !== 0) {
+        operands.add(lvalue.identifier);
+        aliases.union([...operands]);
+        // Update mutable ranges, if the ranges are empty then a reactive scope isn't created
+        for (const operand of operands) {
+          operand.mutableRange.end = makeInstructionId(instr.id + 1);
+        }
+      }
+    }
+  }
+}

compiler/packages/babel-plugin-react-compiler/src/Inference/InferEffectDependencies.ts

@@ -1,8 +1,15 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import * as t from '@babel/types';
 import {CompilerError, SourceLocation} from '..';
 import {
   ArrayExpression,
   Effect,
-  Environment,
   FunctionExpression,
   GeneratedSource,
   HIRFunction,
@@ -14,17 +21,41 @@ import {
   ScopeId,
   ReactiveScopeDependency,
   Place,
+  ReactiveScope,
   ReactiveScopeDependencies,
+  Terminal,
   isUseRefType,
   isSetStateType,
+  isFireFunctionType,
+  makeScopeId,
+  HIR,
+  BasicBlock,
+  BlockId,
+  isEffectEventFunctionType,
 } from '../HIR';
+import {collectHoistablePropertyLoadsInInnerFn} from '../HIR/CollectHoistablePropertyLoads';
+import {collectOptionalChainSidemap} from '../HIR/CollectOptionalChainDependencies';
+import {ReactiveScopeDependencyTreeHIR} from '../HIR/DeriveMinimalDependenciesHIR';
 import {DEFAULT_EXPORT} from '../HIR/Environment';
 import {
   createTemporaryPlace,
   fixScopeAndIdentifierRanges,
   markInstructionIds,
+  markPredecessors,
+  reversePostorderBlocks,
 } from '../HIR/HIRBuilder';
-import {eachInstructionOperand, eachTerminalOperand} from '../HIR/visitors';
+import {
+  collectTemporariesSidemap,
+  DependencyCollectionContext,
+  handleInstruction,
+} from '../HIR/PropagateScopeDependenciesHIR';
+import {buildDependencyInstructions} from '../HIR/ScopeDependencyUtils';
+import {
+  eachInstructionOperand,
+  eachTerminalOperand,
+  terminalFallthrough,
+} from '../HIR/visitors';
+import {empty} from '../Utils/Stack';
 import {getOrInsertWith} from '../Utils/utils';
 
 /**
@@ -32,7 +63,6 @@ import {getOrInsertWith} from '../Utils/utils';
  * a second argument to the useEffect call if no dependency array is provided.
  */
 export function inferEffectDependencies(fn: HIRFunction): void {
-  let hasRewrite = false;
   const fnExpressions = new Map<
     IdentifierId,
     TInstruction<FunctionExpression>
@@ -53,10 +83,7 @@ export function inferEffectDependencies(fn: HIRFunction): void {
   const autodepFnLoads = new Map<IdentifierId, number>();
   const autodepModuleLoads = new Map<IdentifierId, Map<string, number>>();
 
-  const scopeInfos = new Map<
-    ScopeId,
-    {pruned: boolean; deps: ReactiveScopeDependencies; hasSingleInstr: boolean}
-  >();
+  const scopeInfos = new Map<ScopeId, ReactiveScopeDependencies>();
 
   const loadGlobals = new Set<IdentifierId>();
 
@@ -68,23 +95,23 @@ export function inferEffectDependencies(fn: HIRFunction): void {
    * reactive(Identifier i) = Union_{reference of i}(reactive(reference))
    */
   const reactiveIds = inferReactiveIdentifiers(fn);
+  const rewriteBlocks: Array<BasicBlock> = [];
 
   for (const [, block] of fn.body.blocks) {
-    if (
-      block.terminal.kind === 'scope' ||
-      block.terminal.kind === 'pruned-scope'
-    ) {
+    if (block.terminal.kind === 'scope') {
       const scopeBlock = fn.body.blocks.get(block.terminal.block)!;
-      scopeInfos.set(block.terminal.scope.id, {
-        pruned: block.terminal.kind === 'pruned-scope',
-        deps: block.terminal.scope.dependencies,
-        hasSingleInstr:
-          scopeBlock.instructions.length === 1 &&
-          scopeBlock.terminal.kind === 'goto' &&
-          scopeBlock.terminal.block === block.terminal.fallthrough,
-      });
+      if (
+        scopeBlock.instructions.length === 1 &&
+        scopeBlock.terminal.kind === 'goto' &&
+        scopeBlock.terminal.block === block.terminal.fallthrough
+      ) {
+        scopeInfos.set(
+          block.terminal.scope.id,
+          block.terminal.scope.dependencies,
+        );
+      }
     }
-    const rewriteInstrs = new Map<InstructionId, Array<Instruction>>();
+    const rewriteInstrs: Array<SpliceInfo> = [];
     for (const instr of block.instructions) {
       const {value, lvalue} = instr;
       if (value.kind === 'FunctionExpression') {
@@ -148,7 +175,6 @@ export function inferEffectDependencies(fn: HIRFunction): void {
         ) {
           // We have a useEffect call with no deps array, so we need to infer the deps
           const effectDeps: Array<Place> = [];
-          const newInstructions: Array<Instruction> = [];
           const deps: ArrayExpression = {
             kind: 'ArrayExpression',
             elements: effectDeps,
@@ -164,22 +190,12 @@ export function inferEffectDependencies(fn: HIRFunction): void {
               fnExpr.lvalue.identifier.scope != null
                 ? scopeInfos.get(fnExpr.lvalue.identifier.scope.id)
                 : null;
-            CompilerError.invariant(scopeInfo != null, {
-              reason: 'Expected function expression scope to exist',
-              loc: value.loc,
-            });
-            if (scopeInfo.pruned || !scopeInfo.hasSingleInstr) {
-              /**
-               * TODO: retry pipeline that ensures effect function expressions
-               * are placed into their own scope
-               */
-              CompilerError.throwTodo({
-                reason:
-                  '[InferEffectDependencies] Expected effect function to have non-pruned scope and its scope to have exactly one instruction',
-                loc: fnExpr.loc,
-              });
+            let minimalDeps: Set<ReactiveScopeDependency>;
+            if (scopeInfo != null) {
+              minimalDeps = new Set(scopeInfo);
+            } else {
+              minimalDeps = inferMinimalDependencies(fnExpr);
             }
-
             /**
              * Step 1: push dependencies to the effect deps array
              *
@@ -187,128 +203,267 @@ export function inferEffectDependencies(fn: HIRFunction): void {
              * the `infer-effect-deps/pruned-nonreactive-obj` fixture for an
              * explanation.
              */
-            for (const dep of scopeInfo.deps) {
+
+            const usedDeps = [];
+            for (const maybeDep of minimalDeps) {
               if (
-                (isUseRefType(dep.identifier) ||
-                  isSetStateType(dep.identifier)) &&
-                !reactiveIds.has(dep.identifier.id)
+                ((isUseRefType(maybeDep.identifier) ||
+                  isSetStateType(maybeDep.identifier)) &&
+                  !reactiveIds.has(maybeDep.identifier.id)) ||
+                isFireFunctionType(maybeDep.identifier) ||
+                isEffectEventFunctionType(maybeDep.identifier)
               ) {
                 // exclude non-reactive hook results, which will never be in a memo block
                 continue;
               }
 
-              const {place, instructions} = writeDependencyToInstructions(
+              const dep = truncateDepAtCurrent(maybeDep);
+              const {place, value, exitBlockId} = buildDependencyInstructions(
                 dep,
-                reactiveIds.has(dep.identifier.id),
                 fn.env,
-                fnExpr.loc,
               );
-              newInstructions.push(...instructions);
+              rewriteInstrs.push({
+                kind: 'block',
+                location: instr.id,
+                value,
+                exitBlockId: exitBlockId,
+              });
               effectDeps.push(place);
+              usedDeps.push(dep);
             }
 
-            newInstructions.push({
-              id: makeInstructionId(0),
-              loc: GeneratedSource,
-              lvalue: {...depsPlace, effect: Effect.Mutate},
-              value: deps,
-            });
+            // For LSP autodeps feature.
+            const decorations: Array<t.SourceLocation> = [];
+            for (const loc of collectDepUsages(usedDeps, fnExpr.value)) {
+              if (typeof loc === 'symbol') {
+                continue;
+              }
+              decorations.push(loc);
+            }
+            if (typeof value.loc !== 'symbol') {
+              fn.env.logger?.logEvent(fn.env.filename, {
+                kind: 'AutoDepsDecorations',
+                fnLoc: value.loc,
+                decorations,
+              });
+            }
 
             // Step 2: push the inferred deps array as an argument of the useEffect
-            value.args.push({...depsPlace, effect: Effect.Freeze});
-            rewriteInstrs.set(instr.id, newInstructions);
-          } else if (loadGlobals.has(value.args[0].identifier.id)) {
-            // Global functions have no reactive dependencies, so we can insert an empty array
-            newInstructions.push({
-              id: makeInstructionId(0),
-              loc: GeneratedSource,
-              lvalue: {...depsPlace, effect: Effect.Mutate},
-              value: deps,
+            rewriteInstrs.push({
+              kind: 'instr',
+              location: instr.id,
+              value: {
+                id: makeInstructionId(0),
+                loc: GeneratedSource,
+                lvalue: {...depsPlace, effect: Effect.Mutate},
+                value: deps,
+                effects: null,
+              },
             });
             value.args.push({...depsPlace, effect: Effect.Freeze});
-            rewriteInstrs.set(instr.id, newInstructions);
+            fn.env.inferredEffectLocations.add(callee.loc);
+          } else if (loadGlobals.has(value.args[0].identifier.id)) {
+            // Global functions have no reactive dependencies, so we can insert an empty array
+            rewriteInstrs.push({
+              kind: 'instr',
+              location: instr.id,
+              value: {
+                id: makeInstructionId(0),
+                loc: GeneratedSource,
+                lvalue: {...depsPlace, effect: Effect.Mutate},
+                value: deps,
+                effects: null,
+              },
+            });
+            value.args.push({...depsPlace, effect: Effect.Freeze});
+            fn.env.inferredEffectLocations.add(callee.loc);
+          }
+        } else if (
+          value.args.length >= 2 &&
+          value.args.length - 1 === autodepFnLoads.get(callee.identifier.id) &&
+          value.args[0] != null &&
+          value.args[0].kind === 'Identifier'
+        ) {
+          const penultimateArg = value.args[value.args.length - 2];
+          const depArrayArg = value.args[value.args.length - 1];
+          if (
+            depArrayArg.kind !== 'Spread' &&
+            penultimateArg.kind !== 'Spread' &&
+            typeof depArrayArg.loc !== 'symbol' &&
+            typeof penultimateArg.loc !== 'symbol' &&
+            typeof value.loc !== 'symbol'
+          ) {
+            fn.env.logger?.logEvent(fn.env.filename, {
+              kind: 'AutoDepsEligible',
+              fnLoc: value.loc,
+              depArrayLoc: {
+                ...depArrayArg.loc,
+                start: penultimateArg.loc.end,
+                end: depArrayArg.loc.end,
+              },
+            });
           }
         }
       }
     }
-    if (rewriteInstrs.size > 0) {
-      hasRewrite = true;
-      const newInstrs = [];
-      for (const instr of block.instructions) {
-        const newInstr = rewriteInstrs.get(instr.id);
-        if (newInstr != null) {
-          newInstrs.push(...newInstr, instr);
-        } else {
-          newInstrs.push(instr);
-        }
-      }
-      block.instructions = newInstrs;
-    }
+    rewriteSplices(block, rewriteInstrs, rewriteBlocks);
   }
-  if (hasRewrite) {
+
+  if (rewriteBlocks.length > 0) {
+    for (const block of rewriteBlocks) {
+      fn.body.blocks.set(block.id, block);
+    }
+
+    /**
+     * Fixup the HIR to restore RPO, ensure correct predecessors, and renumber
+     * instructions.
+     */
+    reversePostorderBlocks(fn.body);
+    markPredecessors(fn.body);
     // Renumber instructions and fix scope ranges
     markInstructionIds(fn.body);
     fixScopeAndIdentifierRanges(fn.body);
+
+    fn.env.hasInferredEffect = true;
   }
 }
 
-function writeDependencyToInstructions(
+function truncateDepAtCurrent(
   dep: ReactiveScopeDependency,
-  reactive: boolean,
-  env: Environment,
-  loc: SourceLocation,
-): {place: Place; instructions: Array<Instruction>} {
-  const instructions: Array<Instruction> = [];
-  let currValue = createTemporaryPlace(env, GeneratedSource);
-  currValue.reactive = reactive;
-  instructions.push({
-    id: makeInstructionId(0),
-    loc: GeneratedSource,
-    lvalue: {...currValue, effect: Effect.Mutate},
-    value: {
-      kind: 'LoadLocal',
-      place: {
-        kind: 'Identifier',
-        identifier: dep.identifier,
-        effect: Effect.Capture,
-        reactive,
-        loc: loc,
-      },
-      loc: loc,
-    },
-  });
-  for (const path of dep.path) {
-    if (path.optional) {
-      /**
-       * TODO: instead of truncating optional paths, reuse
-       * instructions from hoisted dependencies block(s)
-       */
-      break;
-    }
-    if (path.property === 'current') {
-      /*
-       * Prune ref.current accesses. This may over-capture for non-ref values with
-       * a current property, but that's fine.
-       */
-      break;
-    }
-    const nextValue = createTemporaryPlace(env, GeneratedSource);
-    nextValue.reactive = reactive;
-    instructions.push({
-      id: makeInstructionId(0),
-      loc: GeneratedSource,
-      lvalue: {...nextValue, effect: Effect.Mutate},
-      value: {
-        kind: 'PropertyLoad',
-        object: {...currValue, effect: Effect.Capture},
-        property: path.property,
-        loc: loc,
-      },
-    });
-    currValue = nextValue;
+): ReactiveScopeDependency {
+  const idx = dep.path.findIndex(path => path.property === 'current');
+  if (idx === -1) {
+    return dep;
+  } else {
+    return {...dep, path: dep.path.slice(0, idx)};
   }
-  currValue.effect = Effect.Freeze;
-  return {place: currValue, instructions};
+}
+
+type SpliceInfo =
+  | {kind: 'instr'; location: InstructionId; value: Instruction}
+  | {
+      kind: 'block';
+      location: InstructionId;
+      value: HIR;
+      exitBlockId: BlockId;
+    };
+
+function rewriteSplices(
+  originalBlock: BasicBlock,
+  splices: Array<SpliceInfo>,
+  rewriteBlocks: Array<BasicBlock>,
+): void {
+  if (splices.length === 0) {
+    return;
+  }
+  /**
+   * Splice instructions or value blocks into the original block.
+   * --- original block ---
+   * bb_original
+   *   instr1
+   *   ...
+   *   instr2 <-- splice location
+   *   instr3
+   *   ...
+   *   <original terminal>
+   *
+   * If there is more than one block in the splice, this means that we're
+   * splicing in a set of value-blocks of the following structure:
+   * --- blocks we're splicing in ---
+   * bb_entry:
+   *   instrEntry
+   *   ...
+   *   <splice terminal> fallthrough=bb_exit
+   *
+   * bb1(value):
+   *   ...
+   *
+   * bb_exit:
+   *   instrExit
+   *   ...
+   *   <synthetic terminal>
+   *
+   *
+   * --- rewritten blocks ---
+   * bb_original
+   *   instr1
+   *   ... (original instructions)
+   *   instr2
+   *   instrEntry
+   *   ... (spliced instructions)
+   *   <splice terminal> fallthrough=bb_exit
+   *
+   * bb1(value):
+   *   ...
+   *
+   * bb_exit:
+   *   instrExit
+   *   ... (spliced instructions)
+   *   instr3
+   *   ... (original instructions)
+   *   <original terminal>
+   */
+  const originalInstrs = originalBlock.instructions;
+  let currBlock: BasicBlock = {...originalBlock, instructions: []};
+  rewriteBlocks.push(currBlock);
+
+  let cursor = 0;
+  for (const rewrite of splices) {
+    while (originalInstrs[cursor].id < rewrite.location) {
+      CompilerError.invariant(
+        originalInstrs[cursor].id < originalInstrs[cursor + 1].id,
+        {
+          reason:
+            '[InferEffectDependencies] Internal invariant broken: expected block instructions to be sorted',
+          loc: originalInstrs[cursor].loc,
+        },
+      );
+      currBlock.instructions.push(originalInstrs[cursor]);
+      cursor++;
+    }
+    CompilerError.invariant(originalInstrs[cursor].id === rewrite.location, {
+      reason:
+        '[InferEffectDependencies] Internal invariant broken: splice location not found',
+      loc: originalInstrs[cursor].loc,
+    });
+
+    if (rewrite.kind === 'instr') {
+      currBlock.instructions.push(rewrite.value);
+    } else {
+      const {entry, blocks} = rewrite.value;
+      const entryBlock = blocks.get(entry)!;
+      // splice in all instructions from the entry block
+      currBlock.instructions.push(...entryBlock.instructions);
+      if (blocks.size > 1) {
+        /**
+         * We're splicing in a set of value-blocks, which means we need
+         * to push new blocks and update terminals.
+         */
+        CompilerError.invariant(
+          terminalFallthrough(entryBlock.terminal) === rewrite.exitBlockId,
+          {
+            reason:
+              '[InferEffectDependencies] Internal invariant broken: expected entry block to have a fallthrough',
+            loc: entryBlock.terminal.loc,
+          },
+        );
+        const originalTerminal = currBlock.terminal;
+        currBlock.terminal = entryBlock.terminal;
+
+        for (const [id, block] of blocks) {
+          if (id === entry) {
+            continue;
+          }
+          if (id === rewrite.exitBlockId) {
+            block.terminal = originalTerminal;
+            currBlock = block;
+          }
+          rewriteBlocks.push(block);
+        }
+      }
+    }
+  }
+  currBlock.instructions.push(...originalInstrs.slice(cursor));
 }
 
 function inferReactiveIdentifiers(fn: HIRFunction): Set<IdentifierId> {
@@ -335,3 +490,163 @@ function inferReactiveIdentifiers(fn: HIRFunction): Set<IdentifierId> {
   }
   return reactiveIds;
 }
+
+function collectDepUsages(
+  deps: Array<ReactiveScopeDependency>,
+  fnExpr: FunctionExpression,
+): Array<SourceLocation> {
+  const identifiers: Map<IdentifierId, ReactiveScopeDependency> = new Map();
+  const loadedDeps: Set<IdentifierId> = new Set();
+  const sourceLocations = [];
+  for (const dep of deps) {
+    identifiers.set(dep.identifier.id, dep);
+  }
+
+  for (const [, block] of fnExpr.loweredFunc.func.body.blocks) {
+    for (const instr of block.instructions) {
+      if (
+        instr.value.kind === 'LoadLocal' &&
+        identifiers.has(instr.value.place.identifier.id)
+      ) {
+        loadedDeps.add(instr.lvalue.identifier.id);
+      }
+      for (const place of eachInstructionOperand(instr)) {
+        if (loadedDeps.has(place.identifier.id)) {
+          // TODO(@jbrown215): handle member exprs!!
+          sourceLocations.push(place.identifier.loc);
+        }
+      }
+    }
+  }
+
+  return sourceLocations;
+}
+
+function inferMinimalDependencies(
+  fnInstr: TInstruction<FunctionExpression>,
+): Set<ReactiveScopeDependency> {
+  const fn = fnInstr.value.loweredFunc.func;
+
+  const temporaries = collectTemporariesSidemap(fn, new Set());
+  const {
+    hoistableObjects,
+    processedInstrsInOptional,
+    temporariesReadInOptional,
+  } = collectOptionalChainSidemap(fn);
+
+  const hoistablePropertyLoads = collectHoistablePropertyLoadsInInnerFn(
+    fnInstr,
+    temporaries,
+    hoistableObjects,
+  );
+  const hoistableToFnEntry = hoistablePropertyLoads.get(fn.body.entry);
+  CompilerError.invariant(hoistableToFnEntry != null, {
+    reason:
+      '[InferEffectDependencies] Internal invariant broken: missing entry block',
+    loc: fnInstr.loc,
+  });
+
+  const dependencies = inferDependencies(
+    fnInstr,
+    new Map([...temporaries, ...temporariesReadInOptional]),
+    processedInstrsInOptional,
+  );
+
+  const tree = new ReactiveScopeDependencyTreeHIR(
+    [...hoistableToFnEntry.assumedNonNullObjects].map(o => o.fullPath),
+  );
+  for (const dep of dependencies) {
+    tree.addDependency({...dep});
+  }
+
+  return tree.deriveMinimalDependencies();
+}
+
+function inferDependencies(
+  fnInstr: TInstruction<FunctionExpression>,
+  temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>,
+  processedInstrsInOptional: ReadonlySet<Instruction | Terminal>,
+): Set<ReactiveScopeDependency> {
+  const fn = fnInstr.value.loweredFunc.func;
+  const context = new DependencyCollectionContext(
+    new Set(),
+    temporaries,
+    processedInstrsInOptional,
+  );
+  for (const dep of fn.context) {
+    context.declare(dep.identifier, {
+      id: makeInstructionId(0),
+      scope: empty(),
+    });
+  }
+  const placeholderScope: ReactiveScope = {
+    id: makeScopeId(0),
+    range: {
+      start: fnInstr.id,
+      end: makeInstructionId(fnInstr.id + 1),
+    },
+    dependencies: new Set(),
+    reassignments: new Set(),
+    declarations: new Map(),
+    earlyReturnValue: null,
+    merged: new Set(),
+    loc: GeneratedSource,
+  };
+  context.enterScope(placeholderScope);
+  inferDependenciesInFn(fn, context, temporaries);
+  context.exitScope(placeholderScope, false);
+  const resultUnfiltered = context.deps.get(placeholderScope);
+  CompilerError.invariant(resultUnfiltered != null, {
+    reason:
+      '[InferEffectDependencies] Internal invariant broken: missing scope dependencies',
+    loc: fn.loc,
+  });
+
+  const fnContext = new Set(fn.context.map(dep => dep.identifier.id));
+  const result = new Set<ReactiveScopeDependency>();
+  for (const dep of resultUnfiltered) {
+    if (fnContext.has(dep.identifier.id)) {
+      result.add(dep);
+    }
+  }
+
+  return result;
+}
+
+function inferDependenciesInFn(
+  fn: HIRFunction,
+  context: DependencyCollectionContext,
+  temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>,
+): void {
+  for (const [, block] of fn.body.blocks) {
+    // Record referenced optional chains in phis
+    for (const phi of block.phis) {
+      for (const operand of phi.operands) {
+        const maybeOptionalChain = temporaries.get(operand[1].identifier.id);
+        if (maybeOptionalChain) {
+          context.visitDependency(maybeOptionalChain);
+        }
+      }
+    }
+    for (const instr of block.instructions) {
+      if (
+        instr.value.kind === 'FunctionExpression' ||
+        instr.value.kind === 'ObjectMethod'
+      ) {
+        context.declare(instr.lvalue.identifier, {
+          id: instr.id,
+          scope: context.currentScope,
+        });
+        /**
+         * Recursively visit the inner function to extract dependencies
+         */
+        const innerFn = instr.value.loweredFunc.func;
+        context.enterInnerFn(instr as TInstruction<FunctionExpression>, () => {
+          inferDependenciesInFn(innerFn, context, temporaries);
+        });
+      } else {
+        handleInstruction(instr, context);
+      }
+    }
+  }
+}

compiler/packages/babel-plugin-react-compiler/src/Inference/InferFunctionEffects.ts

@@ -324,7 +324,7 @@ function isEffectSafeOutsideRender(effect: FunctionEffect): boolean {
   return effect.kind === 'GlobalMutation';
 }
 
-function getWriteErrorReason(abstractValue: AbstractValue): string {
+export function getWriteErrorReason(abstractValue: AbstractValue): string {
   if (abstractValue.reason.has(ValueReason.Global)) {
     return 'Writing to a variable defined outside a component or hook is not allowed. Consider using an effect';
   } else if (abstractValue.reason.has(ValueReason.JsxCaptured)) {
@@ -339,6 +339,8 @@ function getWriteErrorReason(abstractValue: AbstractValue): string {
     return "Mutating a value returned from 'useState()', which should not be mutated. Use the setter function to update instead";
   } else if (abstractValue.reason.has(ValueReason.ReducerState)) {
     return "Mutating a value returned from 'useReducer()', which should not be mutated. Use the dispatch function to update instead";
+  } else if (abstractValue.reason.has(ValueReason.Effect)) {
+    return 'Updating a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the mutation before calling useEffect()';
   } else {
     return 'This mutates a variable that React considers immutable';
   }

compiler/packages/babel-plugin-react-compiler/src/Inference/InferMutableLifetimes.ts

@@ -11,7 +11,10 @@ import {
   Identifier,
   InstructionId,
   InstructionKind,
+  isArrayType,
+  isMapType,
   isRefOrRefValue,
+  isSetType,
   makeInstructionId,
   Place,
 } from '../HIR/HIR';
@@ -90,6 +93,17 @@ function inferPlace(
         infer(place, instrId);
       }
       return;
+    case Effect.ConditionallyMutateIterator: {
+      const identifier = place.identifier;
+      if (
+        !isArrayType(identifier) &&
+        !isSetType(identifier) &&
+        !isMapType(identifier)
+      ) {
+        infer(place, instrId);
+      }
+      return;
+    }
     case Effect.ConditionallyMutate:
     case Effect.Mutate: {
       infer(place, instrId);
@@ -162,9 +176,15 @@ export function inferMutableLifetimes(
       if (
         instr.value.kind === 'DeclareContext' ||
         (instr.value.kind === 'StoreContext' &&
-          instr.value.lvalue.kind !== InstructionKind.Reassign)
+          instr.value.lvalue.kind !== InstructionKind.Reassign &&
+          !contextVariableDeclarationInstructions.has(
+            instr.value.lvalue.place.identifier,
+          ))
       ) {
-        // Save declarations of context variables
+        /**
+         * Save declarations of context variables if they hasn't already been
+         * declared (due to hoisted declarations).
+         */
         contextVariableDeclarationInstructions.set(
           instr.value.lvalue.place.identifier,
           instr.id,

compiler/packages/babel-plugin-react-compiler/src/Inference/InferMutableRanges.ts

@@ -6,6 +6,7 @@
  */
 
 import {HIRFunction, Identifier} from '../HIR/HIR';
+import {inferAliasForUncalledFunctions} from './InerAliasForUncalledFunctions';
 import {inferAliases} from './InferAlias';
 import {inferAliasForPhis} from './InferAliasForPhis';
 import {inferAliasForStores} from './InferAliasForStores';
@@ -76,6 +77,7 @@ export function inferMutableRanges(ir: HIRFunction): void {
   while (true) {
     inferMutableRangesForAlias(ir, aliases);
     inferAliasForPhis(ir, aliases);
+    inferAliasForUncalledFunctions(ir, aliases);
     const nextAliases = aliases.canonicalize();
     if (areEqualMaps(prevAliases, nextAliases)) {
       break;
@@ -84,7 +86,7 @@ export function inferMutableRanges(ir: HIRFunction): void {
   }
 }
 
-function areEqualMaps<T>(a: Map<T, T>, b: Map<T, T>): boolean {
+function areEqualMaps<T, U>(a: Map<T, U>, b: Map<T, U>): boolean {
   if (a.size !== b.size) {
     return false;
   }

compiler/packages/babel-plugin-react-compiler/src/Inference/InferMutationAliasingFunctionEffects.ts

@@ -0,0 +1,206 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {HIRFunction, IdentifierId, Place, ValueKind, ValueReason} from '../HIR';
+import {getOrInsertDefault} from '../Utils/utils';
+import {AliasingEffect} from './AliasingEffects';
+
+/**
+ * This function tracks data flow within an inner function expression in order to
+ * compute a set of data-flow aliasing effects describing data flow between the function's
+ * params, context variables, and return value.
+ *
+ * For example, consider the following function expression:
+ *
+ * ```
+ * (x) => { return [x, y] }
+ * ```
+ *
+ * This function captures both param `x` and context variable `y` into the return value.
+ * Unlike our previous inference which counted this as a mutation of x and y, we want to
+ * build a signature for the function that describes the data flow. We would infer
+ * `Capture x -> return, Capture y -> return` effects for this function.
+ *
+ * This function *also* propagates more ambient-style effects (MutateFrozen, MutateGlobal, Impure, Render)
+ * from instructions within the function up to the function itself.
+ */
+export function inferMutationAliasingFunctionEffects(
+  fn: HIRFunction,
+): Array<AliasingEffect> | null {
+  const effects: Array<AliasingEffect> = [];
+
+  /**
+   * Map used to identify tracked variables: params, context vars, return value
+   * This is used to detect mutation/capturing/aliasing of params/context vars
+   */
+  const tracked = new Map<IdentifierId, Place>();
+  tracked.set(fn.returns.identifier.id, fn.returns);
+  for (const operand of [...fn.context, ...fn.params]) {
+    const place = operand.kind === 'Identifier' ? operand : operand.place;
+    tracked.set(place.identifier.id, place);
+  }
+
+  /**
+   * Track capturing/aliasing of context vars and params into each other and into the return.
+   * We don't need to track locals and intermediate values, since we're only concerned with effects
+   * as they relate to arguments visible outside the function.
+   *
+   * For each aliased identifier we track capture/alias/createfrom and then merge this with how
+   * the value is used. Eg capturing an alias => capture. See joinEffects() helper.
+   */
+  type AliasedIdentifier = {
+    kind: AliasingKind;
+    place: Place;
+  };
+  const dataFlow = new Map<IdentifierId, Array<AliasedIdentifier>>();
+
+  /*
+   * Check for aliasing of tracked values. Also joins the effects of how the value is
+   * used (@param kind) with the aliasing type of each value
+   */
+  function lookup(
+    place: Place,
+    kind: AliasedIdentifier['kind'],
+  ): Array<AliasedIdentifier> | null {
+    if (tracked.has(place.identifier.id)) {
+      return [{kind, place}];
+    }
+    return (
+      dataFlow.get(place.identifier.id)?.map(aliased => ({
+        kind: joinEffects(aliased.kind, kind),
+        place: aliased.place,
+      })) ?? null
+    );
+  }
+
+  // todo: fixpoint
+  for (const block of fn.body.blocks.values()) {
+    for (const phi of block.phis) {
+      const operands: Array<AliasedIdentifier> = [];
+      for (const operand of phi.operands.values()) {
+        const inputs = lookup(operand, 'Alias');
+        if (inputs != null) {
+          operands.push(...inputs);
+        }
+      }
+      if (operands.length !== 0) {
+        dataFlow.set(phi.place.identifier.id, operands);
+      }
+    }
+    for (const instr of block.instructions) {
+      if (instr.effects == null) continue;
+      for (const effect of instr.effects) {
+        if (
+          effect.kind === 'Assign' ||
+          effect.kind === 'Capture' ||
+          effect.kind === 'Alias' ||
+          effect.kind === 'CreateFrom'
+        ) {
+          const from = lookup(effect.from, effect.kind);
+          if (from == null) {
+            continue;
+          }
+          const into = lookup(effect.into, 'Alias');
+          if (into == null) {
+            getOrInsertDefault(dataFlow, effect.into.identifier.id, []).push(
+              ...from,
+            );
+          } else {
+            for (const aliased of into) {
+              getOrInsertDefault(
+                dataFlow,
+                aliased.place.identifier.id,
+                [],
+              ).push(...from);
+            }
+          }
+        } else if (
+          effect.kind === 'Create' ||
+          effect.kind === 'CreateFunction'
+        ) {
+          getOrInsertDefault(dataFlow, effect.into.identifier.id, [
+            {kind: 'Alias', place: effect.into},
+          ]);
+        } else if (
+          effect.kind === 'MutateFrozen' ||
+          effect.kind === 'MutateGlobal' ||
+          effect.kind === 'Impure' ||
+          effect.kind === 'Render'
+        ) {
+          effects.push(effect);
+        }
+      }
+    }
+    if (block.terminal.kind === 'return') {
+      const from = lookup(block.terminal.value, 'Alias');
+      if (from != null) {
+        getOrInsertDefault(dataFlow, fn.returns.identifier.id, []).push(
+          ...from,
+        );
+      }
+    }
+  }
+
+  // Create aliasing effects based on observed data flow
+  let hasReturn = false;
+  for (const [into, from] of dataFlow) {
+    const input = tracked.get(into);
+    if (input == null) {
+      continue;
+    }
+    for (const aliased of from) {
+      if (
+        aliased.place.identifier.id === input.identifier.id ||
+        !tracked.has(aliased.place.identifier.id)
+      ) {
+        continue;
+      }
+      const effect = {kind: aliased.kind, from: aliased.place, into: input};
+      effects.push(effect);
+      if (
+        into === fn.returns.identifier.id &&
+        (aliased.kind === 'Assign' || aliased.kind === 'CreateFrom')
+      ) {
+        hasReturn = true;
+      }
+    }
+  }
+  // TODO: more precise return effect inference
+  if (!hasReturn) {
+    effects.unshift({
+      kind: 'Create',
+      into: fn.returns,
+      value:
+        fn.returnType.kind === 'Primitive'
+          ? ValueKind.Primitive
+          : ValueKind.Mutable,
+      reason: ValueReason.KnownReturnSignature,
+    });
+  }
+
+  return effects;
+}
+
+export enum MutationKind {
+  None = 0,
+  Conditional = 1,
+  Definite = 2,
+}
+
+type AliasingKind = 'Alias' | 'Capture' | 'CreateFrom' | 'Assign';
+function joinEffects(
+  effect1: AliasingKind,
+  effect2: AliasingKind,
+): AliasingKind {
+  if (effect1 === 'Capture' || effect2 === 'Capture') {
+    return 'Capture';
+  } else if (effect1 === 'Assign' || effect2 === 'Assign') {
+    return 'Assign';
+  } else {
+    return 'Alias';
+  }
+}

compiler/packages/babel-plugin-react-compiler/src/Inference/InferMutationAliasingRanges.ts

@@ -0,0 +1,737 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import prettyFormat from 'pretty-format';
+import {CompilerError, SourceLocation} from '..';
+import {
+  BlockId,
+  Effect,
+  HIRFunction,
+  Identifier,
+  IdentifierId,
+  InstructionId,
+  makeInstructionId,
+  Place,
+} from '../HIR/HIR';
+import {
+  eachInstructionLValue,
+  eachInstructionValueOperand,
+  eachTerminalOperand,
+} from '../HIR/visitors';
+import {assertExhaustive, getOrInsertWith} from '../Utils/utils';
+import {printFunction} from '../HIR';
+import {printIdentifier, printPlace} from '../HIR/PrintHIR';
+import {MutationKind} from './InferMutationAliasingFunctionEffects';
+import {Result} from '../Utils/Result';
+
+const DEBUG = false;
+const VERBOSE = false;
+
+/**
+ * Infers mutable ranges for all values in the program, using previously inferred
+ * mutation/aliasing effects. This pass builds a data flow graph using the effects,
+ * tracking an abstract notion of "when" each effect occurs relative to the others.
+ * It then walks each mutation effect against the graph, updating the range of each
+ * node that would be reachable at the "time" that the effect occurred.
+ *
+ * This pass also validates against invalid effects: any function that is reachable
+ * by being called, or via a Render effect, is validated against mutating globals
+ * or calling impure code.
+ *
+ * Note that this function also populates the outer function's aliasing effects with
+ * any mutations that apply to its params or context variables. For example, a
+ * function expression such as the following:
+ *
+ * ```
+ * (x) => { x.y = true }
+ * ```
+ *
+ * Would populate a `Mutate x` aliasing effect on the outer function.
+ */
+export function inferMutationAliasingRanges(
+  fn: HIRFunction,
+  {isFunctionExpression}: {isFunctionExpression: boolean},
+): Result<void, CompilerError> {
+  if (VERBOSE) {
+    console.log();
+    console.log(printFunction(fn));
+  }
+  /**
+   * Part 1: Infer mutable ranges for values. We build an abstract model of
+   * values, the alias/capture edges between them, and the set of mutations.
+   * Edges and mutations are ordered, with mutations processed against the
+   * abstract model only after it is fully constructed by visiting all blocks
+   * _and_ connecting phis. Phis are considered ordered at the time of the
+   * phi node.
+   *
+   * This should (may?) mean that mutations are able to see the full state
+   * of the graph and mark all the appropriate identifiers as mutated at
+   * the correct point, accounting for both backward and forward edges.
+   * Ie a mutation of x accounts for both values that flowed into x,
+   * and values that x flowed into.
+   */
+  const state = new AliasingState();
+  type PendingPhiOperand = {from: Place; into: Place; index: number};
+  const pendingPhis = new Map<BlockId, Array<PendingPhiOperand>>();
+  const mutations: Array<{
+    index: number;
+    id: InstructionId;
+    transitive: boolean;
+    kind: MutationKind;
+    place: Place;
+  }> = [];
+  const renders: Array<{index: number; place: Place}> = [];
+
+  let index = 0;
+
+  const errors = new CompilerError();
+
+  for (const param of [...fn.params, ...fn.context, fn.returns]) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    state.create(place, {kind: 'Object'});
+  }
+  const seenBlocks = new Set<BlockId>();
+  for (const block of fn.body.blocks.values()) {
+    for (const phi of block.phis) {
+      state.create(phi.place, {kind: 'Phi'});
+      for (const [pred, operand] of phi.operands) {
+        if (!seenBlocks.has(pred)) {
+          // NOTE: annotation required to actually typecheck and not silently infer `any`
+          const blockPhis = getOrInsertWith<BlockId, Array<PendingPhiOperand>>(
+            pendingPhis,
+            pred,
+            () => [],
+          );
+          blockPhis.push({from: operand, into: phi.place, index: index++});
+        } else {
+          state.assign(index++, operand, phi.place);
+        }
+      }
+    }
+    seenBlocks.add(block.id);
+
+    for (const instr of block.instructions) {
+      if (
+        instr.value.kind === 'FunctionExpression' ||
+        instr.value.kind === 'ObjectMethod'
+      ) {
+        state.create(instr.lvalue, {
+          kind: 'Function',
+          function: instr.value.loweredFunc.func,
+        });
+      } else {
+        for (const lvalue of eachInstructionLValue(instr)) {
+          state.create(lvalue, {kind: 'Object'});
+        }
+      }
+
+      if (instr.effects == null) continue;
+      for (const effect of instr.effects) {
+        if (effect.kind === 'Create') {
+          state.create(effect.into, {kind: 'Object'});
+        } else if (effect.kind === 'CreateFunction') {
+          state.create(effect.into, {
+            kind: 'Function',
+            function: effect.function.loweredFunc.func,
+          });
+        } else if (effect.kind === 'CreateFrom') {
+          state.createFrom(index++, effect.from, effect.into);
+        } else if (effect.kind === 'Assign') {
+          if (!state.nodes.has(effect.into.identifier)) {
+            state.create(effect.into, {kind: 'Object'});
+          }
+          state.assign(index++, effect.from, effect.into);
+        } else if (effect.kind === 'Alias') {
+          state.assign(index++, effect.from, effect.into);
+        } else if (effect.kind === 'Capture') {
+          state.capture(index++, effect.from, effect.into);
+        } else if (
+          effect.kind === 'MutateTransitive' ||
+          effect.kind === 'MutateTransitiveConditionally'
+        ) {
+          mutations.push({
+            index: index++,
+            id: instr.id,
+            transitive: true,
+            kind:
+              effect.kind === 'MutateTransitive'
+                ? MutationKind.Definite
+                : MutationKind.Conditional,
+            place: effect.value,
+          });
+        } else if (
+          effect.kind === 'Mutate' ||
+          effect.kind === 'MutateConditionally'
+        ) {
+          mutations.push({
+            index: index++,
+            id: instr.id,
+            transitive: false,
+            kind:
+              effect.kind === 'Mutate'
+                ? MutationKind.Definite
+                : MutationKind.Conditional,
+            place: effect.value,
+          });
+        } else if (
+          effect.kind === 'MutateFrozen' ||
+          effect.kind === 'MutateGlobal' ||
+          effect.kind === 'Impure'
+        ) {
+          errors.push(effect.error);
+        } else if (effect.kind === 'Render') {
+          renders.push({index: index++, place: effect.place});
+        }
+      }
+    }
+    const blockPhis = pendingPhis.get(block.id);
+    if (blockPhis != null) {
+      for (const {from, into, index} of blockPhis) {
+        state.assign(index, from, into);
+      }
+    }
+    if (block.terminal.kind === 'return') {
+      state.assign(index++, block.terminal.value, fn.returns);
+    }
+
+    if (
+      (block.terminal.kind === 'maybe-throw' ||
+        block.terminal.kind === 'return') &&
+      block.terminal.effects != null
+    ) {
+      for (const effect of block.terminal.effects) {
+        if (effect.kind === 'Alias') {
+          state.assign(index++, effect.from, effect.into);
+        } else {
+          CompilerError.invariant(effect.kind === 'Freeze', {
+            reason: `Unexpected '${effect.kind}' effect for MaybeThrow terminal`,
+            loc: block.terminal.loc,
+          });
+        }
+      }
+    }
+  }
+
+  if (VERBOSE) {
+    console.log(state.debug());
+    console.log(pretty(mutations));
+  }
+  for (const mutation of mutations) {
+    state.mutate(
+      mutation.index,
+      mutation.place.identifier,
+      makeInstructionId(mutation.id + 1),
+      mutation.transitive,
+      mutation.kind,
+      mutation.place.loc,
+      errors,
+    );
+  }
+  for (const render of renders) {
+    state.render(render.index, render.place.identifier, errors);
+  }
+  if (DEBUG) {
+    console.log(pretty([...state.nodes.keys()]));
+  }
+  fn.aliasingEffects ??= [];
+  for (const param of [...fn.context, ...fn.params]) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    const node = state.nodes.get(place.identifier);
+    if (node == null) {
+      continue;
+    }
+    let mutated = false;
+    if (node.local != null) {
+      if (node.local.kind === MutationKind.Conditional) {
+        mutated = true;
+        fn.aliasingEffects.push({
+          kind: 'MutateConditionally',
+          value: {...place, loc: node.local.loc},
+        });
+      } else if (node.local.kind === MutationKind.Definite) {
+        mutated = true;
+        fn.aliasingEffects.push({
+          kind: 'Mutate',
+          value: {...place, loc: node.local.loc},
+        });
+      }
+    }
+    if (node.transitive != null) {
+      if (node.transitive.kind === MutationKind.Conditional) {
+        mutated = true;
+        fn.aliasingEffects.push({
+          kind: 'MutateTransitiveConditionally',
+          value: {...place, loc: node.transitive.loc},
+        });
+      } else if (node.transitive.kind === MutationKind.Definite) {
+        mutated = true;
+        fn.aliasingEffects.push({
+          kind: 'MutateTransitive',
+          value: {...place, loc: node.transitive.loc},
+        });
+      }
+    }
+    if (mutated) {
+      place.effect = Effect.Capture;
+    }
+  }
+
+  /**
+   * Part 2
+   * Add legacy operand-specific effects based on instruction effects and mutable ranges.
+   * Also fixes up operand mutable ranges, making sure that start is non-zero if the value
+   * is mutated (depended on by later passes like InferReactiveScopeVariables which uses this
+   * to filter spurious mutations of globals, which we now guard against more precisely)
+   */
+  for (const block of fn.body.blocks.values()) {
+    for (const phi of block.phis) {
+      // TODO: we don't actually set these effects today!
+      phi.place.effect = Effect.Store;
+      const isPhiMutatedAfterCreation: boolean =
+        phi.place.identifier.mutableRange.end >
+        (block.instructions.at(0)?.id ?? block.terminal.id);
+      for (const operand of phi.operands.values()) {
+        operand.effect = isPhiMutatedAfterCreation
+          ? Effect.Capture
+          : Effect.Read;
+      }
+      if (
+        isPhiMutatedAfterCreation &&
+        phi.place.identifier.mutableRange.start === 0
+      ) {
+        /*
+         * TODO: ideally we'd construct a precise start range, but what really
+         * matters is that the phi's range appears mutable (end > start + 1)
+         * so we just set the start to the previous instruction before this block
+         */
+        const firstInstructionIdOfBlock =
+          block.instructions.at(0)?.id ?? block.terminal.id;
+        phi.place.identifier.mutableRange.start = makeInstructionId(
+          firstInstructionIdOfBlock - 1,
+        );
+      }
+    }
+    for (const instr of block.instructions) {
+      for (const lvalue of eachInstructionLValue(instr)) {
+        lvalue.effect = Effect.ConditionallyMutate;
+        if (lvalue.identifier.mutableRange.start === 0) {
+          lvalue.identifier.mutableRange.start = instr.id;
+        }
+        if (lvalue.identifier.mutableRange.end === 0) {
+          lvalue.identifier.mutableRange.end = makeInstructionId(
+            Math.max(instr.id + 1, lvalue.identifier.mutableRange.end),
+          );
+        }
+      }
+      for (const operand of eachInstructionValueOperand(instr.value)) {
+        operand.effect = Effect.Read;
+      }
+      if (instr.effects == null) {
+        continue;
+      }
+      const operandEffects = new Map<IdentifierId, Effect>();
+      for (const effect of instr.effects) {
+        switch (effect.kind) {
+          case 'Assign':
+          case 'Alias':
+          case 'Capture':
+          case 'CreateFrom': {
+            const isMutatedOrReassigned =
+              effect.into.identifier.mutableRange.end > instr.id;
+            if (isMutatedOrReassigned) {
+              operandEffects.set(effect.from.identifier.id, Effect.Capture);
+              operandEffects.set(effect.into.identifier.id, Effect.Store);
+            } else {
+              operandEffects.set(effect.from.identifier.id, Effect.Read);
+              operandEffects.set(effect.into.identifier.id, Effect.Store);
+            }
+            break;
+          }
+          case 'CreateFunction':
+          case 'Create': {
+            break;
+          }
+          case 'Mutate': {
+            operandEffects.set(effect.value.identifier.id, Effect.Store);
+            break;
+          }
+          case 'Apply': {
+            CompilerError.invariant(false, {
+              reason: `[AnalyzeFunctions] Expected Apply effects to be replaced with more precise effects`,
+              loc: effect.function.loc,
+            });
+          }
+          case 'MutateTransitive':
+          case 'MutateConditionally':
+          case 'MutateTransitiveConditionally': {
+            operandEffects.set(
+              effect.value.identifier.id,
+              Effect.ConditionallyMutate,
+            );
+            break;
+          }
+          case 'Freeze': {
+            operandEffects.set(effect.value.identifier.id, Effect.Freeze);
+            break;
+          }
+          case 'ImmutableCapture': {
+            // no-op, Read is the default
+            break;
+          }
+          case 'Impure':
+          case 'Render':
+          case 'MutateFrozen':
+          case 'MutateGlobal': {
+            // no-op
+            break;
+          }
+          default: {
+            assertExhaustive(
+              effect,
+              `Unexpected effect kind ${(effect as any).kind}`,
+            );
+          }
+        }
+      }
+      for (const lvalue of eachInstructionLValue(instr)) {
+        const effect =
+          operandEffects.get(lvalue.identifier.id) ??
+          Effect.ConditionallyMutate;
+        lvalue.effect = effect;
+      }
+      for (const operand of eachInstructionValueOperand(instr.value)) {
+        if (
+          operand.identifier.mutableRange.end > instr.id &&
+          operand.identifier.mutableRange.start === 0
+        ) {
+          operand.identifier.mutableRange.start = instr.id;
+        }
+        const effect = operandEffects.get(operand.identifier.id) ?? Effect.Read;
+        operand.effect = effect;
+      }
+
+      /**
+       * This case is targeted at hoisted functions like:
+       *
+       * ```
+       * x();
+       * function x() { ... }
+       * ```
+       *
+       * Which turns into:
+       *
+       * t0 = DeclareContext HoistedFunction x
+       * t1 = LoadContext x
+       * t2 = CallExpression t1 ( )
+       * t3 = FunctionExpression ...
+       * t4 = StoreContext Function x = t3
+       *
+       * If the function had captured mutable values, it would already have its
+       * range extended to include the StoreContext. But if the function doesn't
+       * capture any mutable values its range won't have been extended yet. We
+       * want to ensure that the value is memoized along with the context variable,
+       * not independently of it (bc of the way we do codegen for hoisted functions).
+       * So here we check for StoreContext rvalues and if they haven't already had
+       * their range extended to at least this instruction, we extend it.
+       */
+      if (
+        instr.value.kind === 'StoreContext' &&
+        instr.value.value.identifier.mutableRange.end <= instr.id
+      ) {
+        instr.value.value.identifier.mutableRange.end = makeInstructionId(
+          instr.id + 1,
+        );
+      }
+    }
+    if (block.terminal.kind === 'return') {
+      block.terminal.value.effect = isFunctionExpression
+        ? Effect.Read
+        : Effect.Freeze;
+    } else {
+      for (const operand of eachTerminalOperand(block.terminal)) {
+        operand.effect = Effect.Read;
+      }
+    }
+  }
+
+  if (VERBOSE) {
+    console.log(printFunction(fn));
+  }
+  return errors.asResult();
+}
+
+function appendFunctionErrors(errors: CompilerError, fn: HIRFunction): void {
+  for (const effect of fn.aliasingEffects ?? []) {
+    switch (effect.kind) {
+      case 'Impure':
+      case 'MutateFrozen':
+      case 'MutateGlobal': {
+        errors.push(effect.error);
+        break;
+      }
+    }
+  }
+}
+
+type Node = {
+  id: Identifier;
+  createdFrom: Map<Identifier, number>;
+  captures: Map<Identifier, number>;
+  aliases: Map<Identifier, number>;
+  edges: Array<{index: number; node: Identifier; kind: 'capture' | 'alias'}>;
+  transitive: {kind: MutationKind; loc: SourceLocation} | null;
+  local: {kind: MutationKind; loc: SourceLocation} | null;
+  value:
+    | {kind: 'Object'}
+    | {kind: 'Phi'}
+    | {kind: 'Function'; function: HIRFunction};
+};
+class AliasingState {
+  nodes: Map<Identifier, Node> = new Map();
+
+  create(place: Place, value: Node['value']): void {
+    this.nodes.set(place.identifier, {
+      id: place.identifier,
+      createdFrom: new Map(),
+      captures: new Map(),
+      aliases: new Map(),
+      edges: [],
+      transitive: null,
+      local: null,
+      value,
+    });
+  }
+
+  createFrom(index: number, from: Place, into: Place): void {
+    this.create(into, {kind: 'Object'});
+    const fromNode = this.nodes.get(from.identifier);
+    const toNode = this.nodes.get(into.identifier);
+    if (fromNode == null || toNode == null) {
+      if (VERBOSE) {
+        console.log(
+          `skip: createFrom ${printPlace(from)}${!!fromNode} -> ${printPlace(into)}${!!toNode}`,
+        );
+      }
+      return;
+    }
+    fromNode.edges.push({index, node: into.identifier, kind: 'alias'});
+    if (!toNode.createdFrom.has(from.identifier)) {
+      toNode.createdFrom.set(from.identifier, index);
+    }
+  }
+
+  capture(index: number, from: Place, into: Place): void {
+    const fromNode = this.nodes.get(from.identifier);
+    const toNode = this.nodes.get(into.identifier);
+    if (fromNode == null || toNode == null) {
+      if (VERBOSE) {
+        console.log(
+          `skip: capture ${printPlace(from)}${!!fromNode} -> ${printPlace(into)}${!!toNode}`,
+        );
+      }
+      return;
+    }
+    fromNode.edges.push({index, node: into.identifier, kind: 'capture'});
+    if (!toNode.captures.has(from.identifier)) {
+      toNode.captures.set(from.identifier, index);
+    }
+  }
+
+  assign(index: number, from: Place, into: Place): void {
+    const fromNode = this.nodes.get(from.identifier);
+    const toNode = this.nodes.get(into.identifier);
+    if (fromNode == null || toNode == null) {
+      if (VERBOSE) {
+        console.log(
+          `skip: assign ${printPlace(from)}${!!fromNode} -> ${printPlace(into)}${!!toNode}`,
+        );
+      }
+      return;
+    }
+    fromNode.edges.push({index, node: into.identifier, kind: 'alias'});
+    if (!toNode.aliases.has(from.identifier)) {
+      toNode.aliases.set(from.identifier, index);
+    }
+  }
+
+  render(index: number, start: Identifier, errors: CompilerError): void {
+    const seen = new Set<Identifier>();
+    const queue: Array<Identifier> = [start];
+    while (queue.length !== 0) {
+      const current = queue.pop()!;
+      if (seen.has(current)) {
+        continue;
+      }
+      seen.add(current);
+      const node = this.nodes.get(current);
+      if (node == null || node.transitive != null || node.local != null) {
+        continue;
+      }
+      if (node.value.kind === 'Function') {
+        appendFunctionErrors(errors, node.value.function);
+      }
+      for (const [alias, when] of node.createdFrom) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(alias);
+      }
+      for (const [alias, when] of node.aliases) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(alias);
+      }
+      for (const [capture, when] of node.captures) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(capture);
+      }
+    }
+  }
+
+  mutate(
+    index: number,
+    start: Identifier,
+    end: InstructionId,
+    transitive: boolean,
+    kind: MutationKind,
+    loc: SourceLocation,
+    errors: CompilerError,
+  ): void {
+    if (DEBUG) {
+      console.log(
+        `mutate ix=${index} start=$${start.id} end=[${end}]${transitive ? ' transitive' : ''} kind=${kind}`,
+      );
+    }
+    const seen = new Set<Identifier>();
+    const queue: Array<{
+      place: Identifier;
+      transitive: boolean;
+      direction: 'backwards' | 'forwards';
+    }> = [{place: start, transitive, direction: 'backwards'}];
+    while (queue.length !== 0) {
+      const {place: current, transitive, direction} = queue.pop()!;
+      if (seen.has(current)) {
+        continue;
+      }
+      seen.add(current);
+      const node = this.nodes.get(current);
+      if (node == null) {
+        if (DEBUG) {
+          console.log(
+            `no node! ${printIdentifier(start)} for identifier ${printIdentifier(current)}`,
+          );
+        }
+        continue;
+      }
+      if (DEBUG) {
+        console.log(
+          `  mutate $${node.id.id} transitive=${transitive} direction=${direction}`,
+        );
+      }
+      node.id.mutableRange.end = makeInstructionId(
+        Math.max(node.id.mutableRange.end, end),
+      );
+      if (
+        node.value.kind === 'Function' &&
+        node.transitive == null &&
+        node.local == null
+      ) {
+        appendFunctionErrors(errors, node.value.function);
+      }
+      if (transitive) {
+        if (node.transitive == null || node.transitive.kind < kind) {
+          node.transitive = {kind, loc};
+        }
+      } else {
+        if (node.local == null || node.local.kind < kind) {
+          node.local = {kind, loc};
+        }
+      }
+      /**
+       * all mutations affect "forward" edges by the rules:
+       * - Capture a -> b, mutate(a) => mutate(b)
+       * - Alias a -> b, mutate(a) => mutate(b)
+       */
+      for (const edge of node.edges) {
+        if (edge.index >= index) {
+          break;
+        }
+        queue.push({place: edge.node, transitive, direction: 'forwards'});
+      }
+      for (const [alias, when] of node.createdFrom) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push({place: alias, transitive: true, direction: 'backwards'});
+      }
+      if (direction === 'backwards' || node.value.kind !== 'Phi') {
+        /**
+         * all mutations affect backward alias edges by the rules:
+         * - Alias a -> b, mutate(b) => mutate(a)
+         * - Alias a -> b, mutateTransitive(b) => mutate(a)
+         *
+         * However, if we reached a phi because one of its inputs was mutated
+         * (and we're advancing "forwards" through that node's edges), then
+         * we know we've already processed the mutation at its source. The
+         * phi's other inputs can't be affected.
+         */
+        for (const [alias, when] of node.aliases) {
+          if (when >= index) {
+            continue;
+          }
+          queue.push({place: alias, transitive, direction: 'backwards'});
+        }
+      }
+      /**
+       * but only transitive mutations affect captures
+       */
+      if (transitive) {
+        for (const [capture, when] of node.captures) {
+          if (when >= index) {
+            continue;
+          }
+          queue.push({place: capture, transitive, direction: 'backwards'});
+        }
+      }
+    }
+    if (DEBUG) {
+      const nodes = new Map();
+      for (const id of seen) {
+        const node = this.nodes.get(id);
+        nodes.set(id.id, node);
+      }
+      console.log(pretty(nodes));
+    }
+  }
+
+  debug(): string {
+    return pretty(this.nodes);
+  }
+}
+
+export function pretty(v: any): string {
+  return prettyFormat(v, {
+    plugins: [
+      {
+        test: v =>
+          v !== null && typeof v === 'object' && v.kind === 'Identifier',
+        serialize: v => printPlace(v),
+      },
+      {
+        test: v =>
+          v !== null &&
+          typeof v === 'object' &&
+          typeof v.declarationId === 'number',
+        serialize: v =>
+          `${printIdentifier(v)}:${v.mutableRange.start}:${v.mutableRange.end}`,
+      },
+    ],
+  });
+}

compiler/packages/babel-plugin-react-compiler/src/Inference/InferReactivePlaces.ts

@@ -9,18 +9,24 @@ import {CompilerError} from '..';
 import {
   BlockId,
   Effect,
+  Environment,
   HIRFunction,
   Identifier,
   IdentifierId,
+  Instruction,
   Place,
   computePostDominatorTree,
+  evaluatesToStableTypeOrContainer,
   getHookKind,
   isStableType,
+  isStableTypeContainer,
   isUseOperator,
+  isUseRefType,
 } from '../HIR';
 import {PostDominator} from '../HIR/Dominator';
 import {
   eachInstructionLValue,
+  eachInstructionOperand,
   eachInstructionValueOperand,
   eachTerminalOperand,
 } from '../HIR/visitors';
@@ -31,6 +37,103 @@ import {
 import DisjointSet from '../Utils/DisjointSet';
 import {assertExhaustive} from '../Utils/utils';
 
+/**
+ * Side map to track and propagate sources of stability (i.e. hook calls such as
+ * `useRef()` and property reads such as `useState()[1]). Note that this
+ * requires forward data flow analysis since stability is not part of React
+ * Compiler's type system.
+ */
+class StableSidemap {
+  map: Map<IdentifierId, {isStable: boolean}> = new Map();
+  env: Environment;
+
+  constructor(env: Environment) {
+    this.env = env;
+  }
+
+  handleInstruction(instr: Instruction): void {
+    const {value, lvalue} = instr;
+
+    switch (value.kind) {
+      case 'CallExpression':
+      case 'MethodCall': {
+        /**
+         * Sources of stability are known hook calls
+         */
+        if (evaluatesToStableTypeOrContainer(this.env, instr)) {
+          if (isStableType(lvalue.identifier)) {
+            this.map.set(lvalue.identifier.id, {
+              isStable: true,
+            });
+          } else {
+            this.map.set(lvalue.identifier.id, {
+              isStable: false,
+            });
+          }
+        } else if (
+          this.env.config.enableTreatRefLikeIdentifiersAsRefs &&
+          isUseRefType(lvalue.identifier)
+        ) {
+          this.map.set(lvalue.identifier.id, {
+            isStable: true,
+          });
+        }
+        break;
+      }
+
+      case 'Destructure':
+      case 'PropertyLoad': {
+        /**
+         * PropertyLoads may from stable containers may also produce stable
+         * values. ComputedLoads are technically safe for now (as all stable
+         * containers have differently-typed elements), but are not handled as
+         * they should be rare anyways.
+         */
+        const source =
+          value.kind === 'Destructure'
+            ? value.value.identifier.id
+            : value.object.identifier.id;
+        const entry = this.map.get(source);
+        if (entry) {
+          for (const lvalue of eachInstructionLValue(instr)) {
+            if (isStableTypeContainer(lvalue.identifier)) {
+              this.map.set(lvalue.identifier.id, {
+                isStable: false,
+              });
+            } else if (isStableType(lvalue.identifier)) {
+              this.map.set(lvalue.identifier.id, {
+                isStable: true,
+              });
+            }
+          }
+        }
+        break;
+      }
+
+      case 'StoreLocal': {
+        const entry = this.map.get(value.value.identifier.id);
+        if (entry) {
+          this.map.set(lvalue.identifier.id, entry);
+          this.map.set(value.lvalue.place.identifier.id, entry);
+        }
+        break;
+      }
+
+      case 'LoadLocal': {
+        const entry = this.map.get(value.place.identifier.id);
+        if (entry) {
+          this.map.set(lvalue.identifier.id, entry);
+        }
+        break;
+      }
+    }
+  }
+
+  isStable(id: IdentifierId): boolean {
+    const entry = this.map.get(id);
+    return entry != null ? entry.isStable : false;
+  }
+}
 /*
  * Infers which `Place`s are reactive, ie may *semantically* change
  * over the course of the component/hook's lifetime. Places are reactive
@@ -111,6 +214,7 @@ import {assertExhaustive} from '../Utils/utils';
  */
 export function inferReactivePlaces(fn: HIRFunction): void {
   const reactiveIdentifiers = new ReactivityMap(findDisjointMutableValues(fn));
+  const stableIdentifierSources = new StableSidemap(fn.env);
   for (const param of fn.params) {
     const place = param.kind === 'Identifier' ? param : param.place;
     reactiveIdentifiers.markReactive(place);
@@ -184,11 +288,12 @@ export function inferReactivePlaces(fn: HIRFunction): void {
         }
       }
       for (const instruction of block.instructions) {
+        stableIdentifierSources.handleInstruction(instruction);
         const {value} = instruction;
         let hasReactiveInput = false;
         /*
          * NOTE: we want to mark all operands as reactive or not, so we
-         * avoid short-circuting here
+         * avoid short-circuiting here
          */
         for (const operand of eachInstructionValueOperand(value)) {
           const reactive = reactiveIdentifiers.isReactive(operand);
@@ -218,7 +323,13 @@ export function inferReactivePlaces(fn: HIRFunction): void {
 
         if (hasReactiveInput) {
           for (const lvalue of eachInstructionLValue(instruction)) {
-            if (isStableType(lvalue.identifier)) {
+            /**
+             * Note that it's not correct to mark all stable-typed identifiers
+             * as non-reactive, since ternaries and other value blocks can
+             * produce reactive identifiers typed as these.
+             * (e.g. `props.cond ? setState1 : setState2`)
+             */
+            if (stableIdentifierSources.isStable(lvalue.identifier.id)) {
               continue;
             }
             reactiveIdentifiers.markReactive(lvalue);
@@ -230,6 +341,7 @@ export function inferReactivePlaces(fn: HIRFunction): void {
               case Effect.Capture:
               case Effect.Store:
               case Effect.ConditionallyMutate:
+              case Effect.ConditionallyMutateIterator:
               case Effect.Mutate: {
                 if (isMutable(instruction, operand)) {
                   reactiveIdentifiers.markReactive(operand);
@@ -264,6 +376,41 @@ export function inferReactivePlaces(fn: HIRFunction): void {
       }
     }
   } while (reactiveIdentifiers.snapshot());
+
+  function propagateReactivityToInnerFunctions(
+    fn: HIRFunction,
+    isOutermost: boolean,
+  ): void {
+    for (const [, block] of fn.body.blocks) {
+      for (const instr of block.instructions) {
+        if (!isOutermost) {
+          for (const operand of eachInstructionOperand(instr)) {
+            reactiveIdentifiers.isReactive(operand);
+          }
+        }
+        if (
+          instr.value.kind === 'ObjectMethod' ||
+          instr.value.kind === 'FunctionExpression'
+        ) {
+          propagateReactivityToInnerFunctions(
+            instr.value.loweredFunc.func,
+            false,
+          );
+        }
+      }
+      if (!isOutermost) {
+        for (const operand of eachTerminalOperand(block.terminal)) {
+          reactiveIdentifiers.isReactive(operand);
+        }
+      }
+    }
+  }
+
+  /**
+   * Propagate reactivity for inner functions, as we eventually hoist and dedupe
+   * dependency instructions for scopes.
+   */
+  propagateReactivityToInnerFunctions(fn, true);
 }
 
 /*

compiler/packages/babel-plugin-react-compiler/src/Inference/InferReferenceEffects.ts

@@ -12,6 +12,7 @@ import {
   BasicBlock,
   BlockId,
   CallExpression,
+  NewExpression,
   Effect,
   FunctionEffect,
   GeneratedSource,
@@ -23,12 +24,15 @@ import {
   Phi,
   Place,
   SpreadPattern,
+  TInstruction,
   Type,
   ValueKind,
   ValueReason,
   isArrayType,
+  isMapType,
   isMutableEffect,
   isObjectType,
+  isSetType,
 } from '../HIR/HIR';
 import {FunctionSignature} from '../HIR/ObjectShape';
 import {
@@ -38,14 +42,13 @@ import {
   printSourceLocation,
 } from '../HIR/PrintHIR';
 import {
-  eachCallArgument,
   eachInstructionOperand,
   eachInstructionValueOperand,
   eachPatternOperand,
   eachTerminalOperand,
   eachTerminalSuccessor,
 } from '../HIR/visitors';
-import {assertExhaustive} from '../Utils/utils';
+import {assertExhaustive, Set_isSuperset} from '../Utils/utils';
 import {
   inferTerminalFunctionEffects,
   inferInstructionFunctionEffects,
@@ -108,7 +111,10 @@ export default function inferReferenceEffects(
    * Initial state contains function params
    * TODO: include module declarations here as well
    */
-  const initialState = InferenceState.empty(fn.env);
+  const initialState = InferenceState.empty(
+    fn.env,
+    options.isFunctionExpression,
+  );
   const value: InstructionValue = {
     kind: 'Primitive',
     loc: fn.loc,
@@ -251,7 +257,8 @@ type FreezeAction = {values: Set<InstructionValue>; reason: Set<ValueReason>};
 
 // Maintains a mapping of top-level variables to the kind of value they hold
 class InferenceState {
-  #env: Environment;
+  env: Environment;
+  #isFunctionExpression: boolean;
 
   // The kind of each value, based on its allocation site
   #values: Map<InstructionValue, AbstractValue>;
@@ -264,16 +271,25 @@ class InferenceState {
 
   constructor(
     env: Environment,
+    isFunctionExpression: boolean,
     values: Map<InstructionValue, AbstractValue>,
     variables: Map<IdentifierId, Set<InstructionValue>>,
   ) {
-    this.#env = env;
+    this.env = env;
+    this.#isFunctionExpression = isFunctionExpression;
     this.#values = values;
     this.#variables = variables;
   }
 
-  static empty(env: Environment): InferenceState {
-    return new InferenceState(env, new Map(), new Map());
+  static empty(
+    env: Environment,
+    isFunctionExpression: boolean,
+  ): InferenceState {
+    return new InferenceState(env, isFunctionExpression, new Map(), new Map());
+  }
+
+  get isFunctionExpression(): boolean {
+    return this.#isFunctionExpression;
   }
 
   // (Re)initializes a @param value with its default @param kind.
@@ -391,9 +407,14 @@ class InferenceState {
 
   freezeValues(values: Set<InstructionValue>, reason: Set<ValueReason>): void {
     for (const value of values) {
-      if (value.kind === 'DeclareContext') {
+      if (
+        value.kind === 'DeclareContext' ||
+        (value.kind === 'StoreContext' &&
+          (value.lvalue.kind === InstructionKind.Let ||
+            value.lvalue.kind === InstructionKind.Const))
+      ) {
         /**
-         * Avoid freezing hoisted context declarations
+         * Avoid freezing context variable declarations, hoisted or otherwise
          * function Component() {
          *   const cb = useBar(() => foo(2)); // produces a hoisted context declaration
          *   const foo = useFoo();            // reassigns to the context variable
@@ -409,8 +430,8 @@ class InferenceState {
       });
       if (
         value.kind === 'FunctionExpression' &&
-        (this.#env.config.enablePreserveExistingMemoizationGuarantees ||
-          this.#env.config.enableTransitivelyFreezeFunctionExpressions)
+        (this.env.config.enablePreserveExistingMemoizationGuarantees ||
+          this.env.config.enableTransitivelyFreezeFunctionExpressions)
       ) {
         for (const operand of value.loweredFunc.func.context) {
           const operandValues = this.#variables.get(operand.identifier.id);
@@ -468,6 +489,25 @@ class InferenceState {
         }
         break;
       }
+      case Effect.ConditionallyMutateIterator: {
+        if (
+          valueKind.kind === ValueKind.Mutable ||
+          valueKind.kind === ValueKind.Context
+        ) {
+          if (
+            isArrayType(place.identifier) ||
+            isSetType(place.identifier) ||
+            isMapType(place.identifier)
+          ) {
+            effect = Effect.Capture;
+          } else {
+            effect = Effect.ConditionallyMutate;
+          }
+        } else {
+          effect = Effect.Read;
+        }
+        break;
+      }
       case Effect.Mutate: {
         effect = Effect.Mutate;
         break;
@@ -590,7 +630,8 @@ class InferenceState {
       return null;
     } else {
       return new InferenceState(
-        this.#env,
+        this.env,
+        this.#isFunctionExpression,
         nextValues ?? new Map(this.#values),
         nextVariables ?? new Map(this.#variables),
       );
@@ -604,7 +645,8 @@ class InferenceState {
    */
   clone(): InferenceState {
     return new InferenceState(
-      this.#env,
+      this.env,
+      this.#isFunctionExpression,
       new Map(this.#values),
       new Map(this.#variables),
     );
@@ -737,7 +779,7 @@ function inferParam(
  * │         Mutable          │───┘
  * └──────────────────────────┘
  */
-function mergeValues(a: ValueKind, b: ValueKind): ValueKind {
+export function mergeValueKinds(a: ValueKind, b: ValueKind): ValueKind {
   if (a === b) {
     return a;
   } else if (a === ValueKind.MaybeFrozen || b === ValueKind.MaybeFrozen) {
@@ -779,28 +821,16 @@ function mergeValues(a: ValueKind, b: ValueKind): ValueKind {
   }
 }
 
-/**
- * @returns `true` if `a` is a superset of `b`.
- */
-function isSuperset<T>(a: ReadonlySet<T>, b: ReadonlySet<T>): boolean {
-  for (const v of b) {
-    if (!a.has(v)) {
-      return false;
-    }
-  }
-  return true;
-}
-
 function mergeAbstractValues(
   a: AbstractValue,
   b: AbstractValue,
 ): AbstractValue {
-  const kind = mergeValues(a.kind, b.kind);
+  const kind = mergeValueKinds(a.kind, b.kind);
   if (
     kind === a.kind &&
     kind === b.kind &&
-    isSuperset(a.reason, b.reason) &&
-    isSuperset(a.context, b.context)
+    Set_isSuperset(a.reason, b.reason) &&
+    Set_isSuperset(a.context, b.context)
   ) {
     return a;
   }
@@ -879,9 +909,7 @@ function inferBlock(
             state.referenceAndRecordEffects(
               freezeActions,
               element.place,
-              isArrayType(element.place.identifier)
-                ? Effect.Capture
-                : Effect.ConditionallyMutate,
+              Effect.ConditionallyMutateIterator,
               ValueReason.Other,
             );
           } else if (element.kind === 'Identifier') {
@@ -904,43 +932,12 @@ function inferBlock(
         break;
       }
       case 'NewExpression': {
-        /**
-         * For new expressions, we infer a `read` effect on the Class / Function type
-         * to avoid extending mutable ranges of locally created classes, e.g.
-         * ```js
-         * const MyClass = getClass();
-         * const value = new MyClass(val1, val2)
-         *                   ^ (read)   ^ (conditionally mutate)
-         * ```
-         *
-         * Risks:
-         * Classes / functions created during render could technically capture and
-         * mutate their enclosing scope, which we currently do not detect.
-         */
-        const valueKind: AbstractValue = {
-          kind: ValueKind.Mutable,
-          reason: new Set([ValueReason.Other]),
-          context: new Set(),
-        };
-        state.referenceAndRecordEffects(
+        inferCallEffects(
+          state,
+          instr as TInstruction<NewExpression>,
           freezeActions,
-          instrValue.callee,
-          Effect.Read,
-          ValueReason.Other,
+          getFunctionCallSignature(env, instrValue.callee.identifier.type),
         );
-
-        for (const operand of eachCallArgument(instrValue.args)) {
-          state.referenceAndRecordEffects(
-            freezeActions,
-            operand,
-            Effect.ConditionallyMutate,
-            ValueReason.Other,
-          );
-        }
-
-        state.initialize(instrValue, valueKind);
-        state.define(instr.lvalue, instrValue);
-        instr.lvalue.effect = Effect.ConditionallyMutate;
         continuation = {kind: 'funeffects'};
         break;
       }
@@ -1238,62 +1235,12 @@ function inferBlock(
         break;
       }
       case 'CallExpression': {
-        const signature = getFunctionCallSignature(
-          env,
-          instrValue.callee.identifier.type,
+        inferCallEffects(
+          state,
+          instr as TInstruction<CallExpression>,
+          freezeActions,
+          getFunctionCallSignature(env, instrValue.callee.identifier.type),
         );
-
-        const effects =
-          signature !== null ? getFunctionEffects(instrValue, signature) : null;
-        const returnValueKind: AbstractValue =
-          signature !== null
-            ? {
-                kind: signature.returnValueKind,
-                reason: new Set([
-                  signature.returnValueReason ??
-                    ValueReason.KnownReturnSignature,
-                ]),
-                context: new Set(),
-              }
-            : {
-                kind: ValueKind.Mutable,
-                reason: new Set([ValueReason.Other]),
-                context: new Set(),
-              };
-        let hasCaptureArgument = false;
-        for (let i = 0; i < instrValue.args.length; i++) {
-          const arg = instrValue.args[i];
-          const place = arg.kind === 'Identifier' ? arg : arg.place;
-          state.referenceAndRecordEffects(
-            freezeActions,
-            place,
-            getArgumentEffect(effects != null ? effects[i] : null, arg),
-            ValueReason.Other,
-          );
-          hasCaptureArgument ||= place.effect === Effect.Capture;
-        }
-        if (signature !== null) {
-          state.referenceAndRecordEffects(
-            freezeActions,
-            instrValue.callee,
-            signature.calleeEffect,
-            ValueReason.Other,
-          );
-        } else {
-          state.referenceAndRecordEffects(
-            freezeActions,
-            instrValue.callee,
-            Effect.ConditionallyMutate,
-            ValueReason.Other,
-          );
-        }
-        hasCaptureArgument ||= instrValue.callee.effect === Effect.Capture;
-
-        state.initialize(instrValue, returnValueKind);
-        state.define(instr.lvalue, instrValue);
-        instr.lvalue.effect = hasCaptureArgument
-          ? Effect.Store
-          : Effect.ConditionallyMutate;
         continuation = {kind: 'funeffects'};
         break;
       }
@@ -1311,102 +1258,12 @@ function inferBlock(
           Effect.Read,
           ValueReason.Other,
         );
-
-        const signature = getFunctionCallSignature(
-          env,
-          instrValue.property.identifier.type,
+        inferCallEffects(
+          state,
+          instr as TInstruction<MethodCall>,
+          freezeActions,
+          getFunctionCallSignature(env, instrValue.property.identifier.type),
         );
-
-        const returnValueKind: AbstractValue =
-          signature !== null
-            ? {
-                kind: signature.returnValueKind,
-                reason: new Set([
-                  signature.returnValueReason ??
-                    ValueReason.KnownReturnSignature,
-                ]),
-                context: new Set(),
-              }
-            : {
-                kind: ValueKind.Mutable,
-                reason: new Set([ValueReason.Other]),
-                context: new Set(),
-              };
-
-        if (
-          signature !== null &&
-          signature.mutableOnlyIfOperandsAreMutable &&
-          areArgumentsImmutableAndNonMutating(state, instrValue.args)
-        ) {
-          /*
-           * None of the args are mutable or mutate their params, we can downgrade to
-           * treating as all reads (except that the receiver may be captured)
-           */
-          for (const arg of instrValue.args) {
-            const place = arg.kind === 'Identifier' ? arg : arg.place;
-            state.referenceAndRecordEffects(
-              freezeActions,
-              place,
-              Effect.Read,
-              ValueReason.Other,
-            );
-          }
-          state.referenceAndRecordEffects(
-            freezeActions,
-            instrValue.receiver,
-            Effect.Capture,
-            ValueReason.Other,
-          );
-          state.initialize(instrValue, returnValueKind);
-          state.define(instr.lvalue, instrValue);
-          instr.lvalue.effect =
-            instrValue.receiver.effect === Effect.Capture
-              ? Effect.Store
-              : Effect.ConditionallyMutate;
-          continuation = {kind: 'funeffects'};
-          break;
-        }
-
-        const effects =
-          signature !== null ? getFunctionEffects(instrValue, signature) : null;
-        let hasCaptureArgument = false;
-        for (let i = 0; i < instrValue.args.length; i++) {
-          const arg = instrValue.args[i];
-          const place = arg.kind === 'Identifier' ? arg : arg.place;
-          /*
-           * If effects are inferred for an argument, we should fail invalid
-           * mutating effects
-           */
-          state.referenceAndRecordEffects(
-            freezeActions,
-            place,
-            getArgumentEffect(effects != null ? effects[i] : null, arg),
-            ValueReason.Other,
-          );
-          hasCaptureArgument ||= place.effect === Effect.Capture;
-        }
-        if (signature !== null) {
-          state.referenceAndRecordEffects(
-            freezeActions,
-            instrValue.receiver,
-            signature.calleeEffect,
-            ValueReason.Other,
-          );
-        } else {
-          state.referenceAndRecordEffects(
-            freezeActions,
-            instrValue.receiver,
-            Effect.ConditionallyMutate,
-            ValueReason.Other,
-          );
-        }
-        hasCaptureArgument ||= instrValue.receiver.effect === Effect.Capture;
-
-        state.initialize(instrValue, returnValueKind);
-        state.define(instr.lvalue, instrValue);
-        instr.lvalue.effect = hasCaptureArgument
-          ? Effect.Store
-          : Effect.ConditionallyMutate;
         continuation = {kind: 'funeffects'};
         break;
       }
@@ -1742,6 +1599,14 @@ function inferBlock(
         );
 
         const lvalue = instr.lvalue;
+        if (instrValue.lvalue.kind !== InstructionKind.Reassign) {
+          state.initialize(instrValue, {
+            kind: ValueKind.Mutable,
+            reason: new Set([ValueReason.Other]),
+            context: new Set(),
+          });
+          state.define(instrValue.lvalue.place, instrValue);
+        }
         state.alias(lvalue, instrValue.value);
         lvalue.effect = Effect.Store;
         continuation = {kind: 'funeffects'};
@@ -1813,7 +1678,13 @@ function inferBlock(
           kind === ValueKind.Mutable || kind === ValueKind.Context;
         let effect;
         let valueKind: AbstractValue;
-        if (!isMutable || isArrayType(instrValue.collection.identifier)) {
+        const iterator = instrValue.collection.identifier;
+        if (
+          !isMutable ||
+          isArrayType(iterator) ||
+          isMapType(iterator) ||
+          isSetType(iterator)
+        ) {
           // Case 1, assume iterator is a separate mutable object
           effect = {
             kind: Effect.Read,
@@ -1854,7 +1725,7 @@ function inferBlock(
         state.referenceAndRecordEffects(
           freezeActions,
           instrValue.iterator,
-          Effect.ConditionallyMutate,
+          Effect.ConditionallyMutateIterator,
           ValueReason.Other,
         );
         /**
@@ -1926,8 +1797,15 @@ function inferBlock(
     if (block.terminal.kind === 'return' || block.terminal.kind === 'throw') {
       if (
         state.isDefined(operand) &&
-        state.kind(operand).kind === ValueKind.Context
+        ((operand.identifier.type.kind === 'Function' &&
+          state.isFunctionExpression) ||
+          state.kind(operand).kind === ValueKind.Context)
       ) {
+        /**
+         * Returned values should only be typed as 'frozen' if they are both (1)
+         * local and (2) not a function expression which may capture and mutate
+         * this function's outer context.
+         */
         effect = Effect.ConditionallyMutate;
       } else {
         effect = Effect.Freeze;
@@ -1983,7 +1861,7 @@ export function getFunctionCallSignature(
  * @returns Inferred effects of function arguments, or null if inference fails.
  */
 export function getFunctionEffects(
-  fn: MethodCall | CallExpression,
+  fn: MethodCall | CallExpression | NewExpression,
   sig: FunctionSignature,
 ): Array<Effect> | null {
   const results = [];
@@ -2012,6 +1890,33 @@ export function getFunctionEffects(
   return results;
 }
 
+export function isKnownMutableEffect(effect: Effect): boolean {
+  switch (effect) {
+    case Effect.Store:
+    case Effect.ConditionallyMutate:
+    case Effect.ConditionallyMutateIterator:
+    case Effect.Mutate: {
+      return true;
+    }
+
+    case Effect.Unknown: {
+      CompilerError.invariant(false, {
+        reason: 'Unexpected unknown effect',
+        description: null,
+        loc: GeneratedSource,
+        suggestions: null,
+      });
+    }
+    case Effect.Read:
+    case Effect.Capture:
+    case Effect.Freeze: {
+      return false;
+    }
+    default: {
+      assertExhaustive(effect, `Unexpected effect \`${effect}\``);
+    }
+  }
+}
 /**
  * Returns true if all of the arguments are both non-mutable (immutable or frozen)
  * _and_ are not functions which might mutate their arguments. Note that function
@@ -2023,10 +1928,20 @@ function areArgumentsImmutableAndNonMutating(
   args: MethodCall['args'],
 ): boolean {
   for (const arg of args) {
+    if (arg.kind === 'Identifier' && arg.identifier.type.kind === 'Function') {
+      const fnShape = state.env.getFunctionSignature(arg.identifier.type);
+      if (fnShape != null) {
+        return (
+          !fnShape.positionalParams.some(isKnownMutableEffect) &&
+          (fnShape.restParam == null ||
+            !isKnownMutableEffect(fnShape.restParam))
+        );
+      }
+    }
     const place = arg.kind === 'Identifier' ? arg : arg.place;
+
     const kind = state.kind(place).kind;
     switch (kind) {
-      case ValueKind.Global:
       case ValueKind.Primitive:
       case ValueKind.Frozen: {
         /*
@@ -2037,6 +1952,10 @@ function areArgumentsImmutableAndNonMutating(
         break;
       }
       default: {
+        /**
+         * Globals, module locals, and other locally defined functions may
+         * mutate their arguments.
+         */
         return false;
       }
     }
@@ -2058,7 +1977,7 @@ function areArgumentsImmutableAndNonMutating(
   return true;
 }
 
-function getArgumentEffect(
+export function getArgumentEffect(
   signatureEffect: Effect | null,
   arg: Place | SpreadPattern,
 ): Effect {
@@ -2079,9 +1998,128 @@ function getArgumentEffect(
         });
       }
       // effects[i] is Effect.Capture | Effect.Read | Effect.Store
-      return Effect.ConditionallyMutate;
+      return Effect.ConditionallyMutateIterator;
     }
   } else {
     return Effect.ConditionallyMutate;
   }
 }
+
+function inferCallEffects(
+  state: InferenceState,
+  instr:
+    | TInstruction<CallExpression>
+    | TInstruction<MethodCall>
+    | TInstruction<NewExpression>,
+  freezeActions: Array<FreezeAction>,
+  signature: FunctionSignature | null,
+): void {
+  const instrValue = instr.value;
+  const returnValueKind: AbstractValue =
+    signature !== null
+      ? {
+          kind: signature.returnValueKind,
+          reason: new Set([
+            signature.returnValueReason ?? ValueReason.KnownReturnSignature,
+          ]),
+          context: new Set(),
+        }
+      : {
+          kind: ValueKind.Mutable,
+          reason: new Set([ValueReason.Other]),
+          context: new Set(),
+        };
+
+  if (
+    instrValue.kind === 'MethodCall' &&
+    signature !== null &&
+    signature.mutableOnlyIfOperandsAreMutable &&
+    areArgumentsImmutableAndNonMutating(state, instrValue.args)
+  ) {
+    /*
+     * None of the args are mutable or mutate their params, we can downgrade to
+     * treating as all reads (except that the receiver may be captured)
+     */
+    for (const arg of instrValue.args) {
+      const place = arg.kind === 'Identifier' ? arg : arg.place;
+      state.referenceAndRecordEffects(
+        freezeActions,
+        place,
+        Effect.Read,
+        ValueReason.Other,
+      );
+    }
+    state.referenceAndRecordEffects(
+      freezeActions,
+      instrValue.receiver,
+      Effect.Capture,
+      ValueReason.Other,
+    );
+    state.initialize(instrValue, returnValueKind);
+    state.define(instr.lvalue, instrValue);
+    instr.lvalue.effect =
+      instrValue.receiver.effect === Effect.Capture
+        ? Effect.Store
+        : Effect.ConditionallyMutate;
+    return;
+  }
+
+  const effects =
+    signature !== null ? getFunctionEffects(instrValue, signature) : null;
+  let hasCaptureArgument = false;
+  for (let i = 0; i < instrValue.args.length; i++) {
+    const arg = instrValue.args[i];
+    const place = arg.kind === 'Identifier' ? arg : arg.place;
+    /*
+     * If effects are inferred for an argument, we should fail invalid
+     * mutating effects
+     */
+    state.referenceAndRecordEffects(
+      freezeActions,
+      place,
+      getArgumentEffect(effects != null ? effects[i] : null, arg),
+      ValueReason.Other,
+    );
+    hasCaptureArgument ||= place.effect === Effect.Capture;
+  }
+  const callee =
+    instrValue.kind === 'MethodCall' ? instrValue.receiver : instrValue.callee;
+  if (signature !== null) {
+    state.referenceAndRecordEffects(
+      freezeActions,
+      callee,
+      signature.calleeEffect,
+      ValueReason.Other,
+    );
+  } else {
+    /**
+     * For new expressions, we infer a `read` effect on the Class / Function type
+     * to avoid extending mutable ranges of locally created classes, e.g.
+     * ```js
+     * const MyClass = getClass();
+     * const value = new MyClass(val1, val2)
+     *                   ^ (read)   ^ (conditionally mutate)
+     * ```
+     *
+     * Risks:
+     * Classes / functions created during render could technically capture and
+     * mutate their enclosing scope, which we currently do not detect.
+     */
+
+    state.referenceAndRecordEffects(
+      freezeActions,
+      callee,
+      instrValue.kind === 'NewExpression'
+        ? Effect.Read
+        : Effect.ConditionallyMutate,
+      ValueReason.Other,
+    );
+  }
+  hasCaptureArgument ||= callee.effect === Effect.Capture;
+
+  state.initialize(instrValue, returnValueKind);
+  state.define(instr.lvalue, instrValue);
+  instr.lvalue.effect = hasCaptureArgument
+    ? Effect.Store
+    : Effect.ConditionallyMutate;
+}

compiler/packages/babel-plugin-react-compiler/src/Inference/InlineImmediatelyInvokedFunctionExpressions.ts

@@ -17,6 +17,7 @@ import {
   InstructionKind,
   LabelTerminal,
   Place,
+  isStatementBlockKind,
   makeInstructionId,
   promoteTemporary,
   reversePostorderBlocks,
@@ -90,100 +91,106 @@ export function inlineImmediatelyInvokedFunctionExpressions(
    */
   const queue = Array.from(fn.body.blocks.values());
   queue: for (const block of queue) {
-    for (let ii = 0; ii < block.instructions.length; ii++) {
-      const instr = block.instructions[ii]!;
-      switch (instr.value.kind) {
-        case 'FunctionExpression': {
-          if (instr.lvalue.identifier.name === null) {
-            functions.set(instr.lvalue.identifier.id, instr.value);
+    /*
+     * We can't handle labels inside expressions yet, so we don't inline IIFEs if they are in an
+     * expression block.
+     */
+    if (isStatementBlockKind(block.kind)) {
+      for (let ii = 0; ii < block.instructions.length; ii++) {
+        const instr = block.instructions[ii]!;
+        switch (instr.value.kind) {
+          case 'FunctionExpression': {
+            if (instr.lvalue.identifier.name === null) {
+              functions.set(instr.lvalue.identifier.id, instr.value);
+            }
+            break;
           }
-          break;
-        }
-        case 'CallExpression': {
-          if (instr.value.args.length !== 0) {
-            // We don't support inlining when there are arguments
-            continue;
+          case 'CallExpression': {
+            if (instr.value.args.length !== 0) {
+              // We don't support inlining when there are arguments
+              continue;
+            }
+            const body = functions.get(instr.value.callee.identifier.id);
+            if (body === undefined) {
+              // Not invoking a local function expression, can't inline
+              continue;
+            }
+
+            if (
+              body.loweredFunc.func.params.length > 0 ||
+              body.loweredFunc.func.async ||
+              body.loweredFunc.func.generator
+            ) {
+              // Can't inline functions with params, or async/generator functions
+              continue;
+            }
+
+            // We know this function is used for an IIFE and can prune it later
+            inlinedFunctions.add(instr.value.callee.identifier.id);
+
+            // Create a new block which will contain code following the IIFE call
+            const continuationBlockId = fn.env.nextBlockId;
+            const continuationBlock: BasicBlock = {
+              id: continuationBlockId,
+              instructions: block.instructions.slice(ii + 1),
+              kind: block.kind,
+              phis: new Set(),
+              preds: new Set(),
+              terminal: block.terminal,
+            };
+            fn.body.blocks.set(continuationBlockId, continuationBlock);
+
+            /*
+             * Trim the original block to contain instructions up to (but not including)
+             * the IIFE
+             */
+            block.instructions.length = ii;
+
+            /*
+             * To account for complex control flow within the lambda, we treat the lambda
+             * as if it were a single labeled statement, and replace all returns with gotos
+             * to the label fallthrough.
+             */
+            const newTerminal: LabelTerminal = {
+              block: body.loweredFunc.func.body.entry,
+              id: makeInstructionId(0),
+              kind: 'label',
+              fallthrough: continuationBlockId,
+              loc: block.terminal.loc,
+            };
+            block.terminal = newTerminal;
+
+            // We store the result in the IIFE temporary
+            const result = instr.lvalue;
+
+            // Declare the IIFE temporary
+            declareTemporary(fn.env, block, result);
+
+            // Promote the temporary with a name as we require this to persist
+            promoteTemporary(result.identifier);
+
+            /*
+             * Rewrite blocks from the lambda to replace any `return` with a
+             * store to the result and `goto` the continuation block
+             */
+            for (const [id, block] of body.loweredFunc.func.body.blocks) {
+              block.preds.clear();
+              rewriteBlock(fn.env, block, continuationBlockId, result);
+              fn.body.blocks.set(id, block);
+            }
+
+            /*
+             * Ensure we visit the continuation block, since there may have been
+             * sequential IIFEs that need to be visited.
+             */
+            queue.push(continuationBlock);
+            continue queue;
           }
-          const body = functions.get(instr.value.callee.identifier.id);
-          if (body === undefined) {
-            // Not invoking a local function expression, can't inline
-            continue;
-          }
-
-          if (
-            body.loweredFunc.func.params.length > 0 ||
-            body.loweredFunc.func.async ||
-            body.loweredFunc.func.generator
-          ) {
-            // Can't inline functions with params, or async/generator functions
-            continue;
-          }
-
-          // We know this function is used for an IIFE and can prune it later
-          inlinedFunctions.add(instr.value.callee.identifier.id);
-
-          // Create a new block which will contain code following the IIFE call
-          const continuationBlockId = fn.env.nextBlockId;
-          const continuationBlock: BasicBlock = {
-            id: continuationBlockId,
-            instructions: block.instructions.slice(ii + 1),
-            kind: block.kind,
-            phis: new Set(),
-            preds: new Set(),
-            terminal: block.terminal,
-          };
-          fn.body.blocks.set(continuationBlockId, continuationBlock);
-
-          /*
-           * Trim the original block to contain instructions up to (but not including)
-           * the IIFE
-           */
-          block.instructions.length = ii;
-
-          /*
-           * To account for complex control flow within the lambda, we treat the lambda
-           * as if it were a single labeled statement, and replace all returns with gotos
-           * to the label fallthrough.
-           */
-          const newTerminal: LabelTerminal = {
-            block: body.loweredFunc.func.body.entry,
-            id: makeInstructionId(0),
-            kind: 'label',
-            fallthrough: continuationBlockId,
-            loc: block.terminal.loc,
-          };
-          block.terminal = newTerminal;
-
-          // We store the result in the IIFE temporary
-          const result = instr.lvalue;
-
-          // Declare the IIFE temporary
-          declareTemporary(fn.env, block, result);
-
-          // Promote the temporary with a name as we require this to persist
-          promoteTemporary(result.identifier);
-
-          /*
-           * Rewrite blocks from the lambda to replace any `return` with a
-           * store to the result and `goto` the continuation block
-           */
-          for (const [id, block] of body.loweredFunc.func.body.blocks) {
-            block.preds.clear();
-            rewriteBlock(fn.env, block, continuationBlockId, result);
-            fn.body.blocks.set(id, block);
-          }
-
-          /*
-           * Ensure we visit the continuation block, since there may have been
-           * sequential IIFEs that need to be visited.
-           */
-          queue.push(continuationBlock);
-          continue queue;
-        }
-        default: {
-          for (const place of eachInstructionValueOperand(instr.value)) {
-            // Any other use of a function expression means it isn't an IIFE
-            functions.delete(place.identifier.id);
+          default: {
+            for (const place of eachInstructionValueOperand(instr.value)) {
+              // Any other use of a function expression means it isn't an IIFE
+              functions.delete(place.identifier.id);
+            }
           }
         }
       }
@@ -235,6 +242,7 @@ function rewriteBlock(
       type: null,
       loc: terminal.loc,
     },
+    effects: null,
   });
   block.terminal = {
     kind: 'goto',
@@ -263,5 +271,6 @@ function declareTemporary(
       type: null,
       loc: result.loc,
     },
+    effects: null,
   });
 }

compiler/packages/babel-plugin-react-compiler/src/Optimization/ConstantPropagation.ts

@@ -327,6 +327,23 @@ function evaluateInstruction(
           }
           return null;
         }
+        case '-': {
+          const operand = read(constants, value.value);
+          if (
+            operand !== null &&
+            operand.kind === 'Primitive' &&
+            typeof operand.value === 'number'
+          ) {
+            const result: Primitive = {
+              kind: 'Primitive',
+              value: operand.value * -1,
+              loc: value.loc,
+            };
+            instr.value = result;
+            return result;
+          }
+          return null;
+        }
         default:
           return null;
       }
@@ -492,6 +509,73 @@ function evaluateInstruction(
       }
       return null;
     }
+    case 'TemplateLiteral': {
+      if (value.subexprs.length === 0) {
+        const result: InstructionValue = {
+          kind: 'Primitive',
+          value: value.quasis.map(q => q.cooked).join(''),
+          loc: value.loc,
+        };
+        instr.value = result;
+        return result;
+      }
+
+      if (value.subexprs.length !== value.quasis.length - 1) {
+        return null;
+      }
+
+      if (value.quasis.some(q => q.cooked === undefined)) {
+        return null;
+      }
+
+      let quasiIndex = 0;
+      let resultString = value.quasis[quasiIndex].cooked as string;
+      ++quasiIndex;
+
+      for (const subExpr of value.subexprs) {
+        const subExprValue = read(constants, subExpr);
+        if (!subExprValue || subExprValue.kind !== 'Primitive') {
+          return null;
+        }
+
+        const expressionValue = subExprValue.value;
+        if (
+          typeof expressionValue !== 'number' &&
+          typeof expressionValue !== 'string' &&
+          typeof expressionValue !== 'boolean' &&
+          !(typeof expressionValue === 'object' && expressionValue === null)
+        ) {
+          // value is not supported (function, object) or invalid (symbol), or something else
+          return null;
+        }
+
+        const suffix = value.quasis[quasiIndex].cooked;
+        ++quasiIndex;
+
+        if (suffix === undefined) {
+          return null;
+        }
+
+        /*
+         * Spec states that concat calls ToString(argument) internally on its parameters
+         * -> we don't have to implement ToString(argument) ourselves and just use the engine implementation
+         * Refs:
+         *  - https://tc39.es/ecma262/2024/#sec-tostring
+         *  - https://tc39.es/ecma262/2024/#sec-string.prototype.concat
+         *  - https://tc39.es/ecma262/2024/#sec-template-literals-runtime-semantics-evaluation
+         */
+        resultString = resultString.concat(expressionValue as string, suffix);
+      }
+
+      const result: InstructionValue = {
+        kind: 'Primitive',
+        value: resultString,
+        loc: value.loc,
+      };
+
+      instr.value = result;
+      return result;
+    }
     case 'LoadLocal': {
       const placeValue = read(constants, value.place);
       if (placeValue !== null) {

compiler/packages/babel-plugin-react-compiler/src/Optimization/InlineJsxTransform.ts

@@ -151,6 +151,7 @@ export function inlineJsxTransform(
               type: null,
               loc: instr.value.loc,
             },
+            effects: null,
             loc: instr.loc,
           };
           currentBlockInstructions.push(varInstruction);
@@ -167,6 +168,7 @@ export function inlineJsxTransform(
               },
               loc: instr.value.loc,
             },
+            effects: null,
             loc: instr.loc,
           };
           currentBlockInstructions.push(devGlobalInstruction);
@@ -220,6 +222,7 @@ export function inlineJsxTransform(
               type: null,
               loc: instr.value.loc,
             },
+            effects: null,
             loc: instr.loc,
           };
           thenBlockInstructions.push(reassignElseInstruction);
@@ -292,6 +295,7 @@ export function inlineJsxTransform(
               ],
               loc: instr.value.loc,
             },
+            effects: null,
             loc: instr.loc,
           };
           elseBlockInstructions.push(reactElementInstruction);
@@ -309,6 +313,7 @@ export function inlineJsxTransform(
               type: null,
               loc: instr.value.loc,
             },
+            effects: null,
             loc: instr.loc,
           };
           elseBlockInstructions.push(reassignConditionalInstruction);
@@ -436,6 +441,7 @@ function createSymbolProperty(
       binding: {kind: 'Global', name: 'Symbol'},
       loc: instr.value.loc,
     },
+    effects: null,
     loc: instr.loc,
   };
   nextInstructions.push(symbolInstruction);
@@ -450,6 +456,7 @@ function createSymbolProperty(
       property: makePropertyLiteral('for'),
       loc: instr.value.loc,
     },
+    effects: null,
     loc: instr.loc,
   };
   nextInstructions.push(symbolForInstruction);
@@ -463,6 +470,7 @@ function createSymbolProperty(
       value: symbolName,
       loc: instr.value.loc,
     },
+    effects: null,
     loc: instr.loc,
   };
   nextInstructions.push(symbolValueInstruction);
@@ -478,6 +486,7 @@ function createSymbolProperty(
       args: [symbolValueInstruction.lvalue],
       loc: instr.value.loc,
     },
+    effects: null,
     loc: instr.loc,
   };
   const $$typeofProperty: ObjectProperty = {
@@ -508,6 +517,7 @@ function createTagProperty(
           value: componentTag.name,
           loc: instr.value.loc,
         },
+        effects: null,
         loc: instr.loc,
       };
       tagProperty = {
@@ -634,6 +644,7 @@ function createPropsProperties(
           elements: [...children],
           loc: instr.value.loc,
         },
+        effects: null,
         loc: instr.loc,
       };
       nextInstructions.push(childrenPropInstruction);
@@ -657,6 +668,7 @@ function createPropsProperties(
         value: null,
         loc: instr.value.loc,
       },
+      effects: null,
       loc: instr.loc,
     };
     refProperty = {
@@ -678,6 +690,7 @@ function createPropsProperties(
         value: null,
         loc: instr.value.loc,
       },
+      effects: null,
       loc: instr.loc,
     };
     keyProperty = {
@@ -711,6 +724,7 @@ function createPropsProperties(
         properties: props,
         loc: instr.value.loc,
       },
+      effects: null,
       loc: instr.loc,
     };
     propsProperty = {

compiler/packages/babel-plugin-react-compiler/src/Optimization/LowerContextAccess.ts

@@ -18,6 +18,7 @@ import {
   Instruction,
   LoadGlobal,
   LoadLocal,
+  NonLocalImportSpecifier,
   Place,
   PropertyLoad,
   isUseContextHookType,
@@ -35,7 +36,7 @@ import {inferTypes} from '../TypeInference';
 
 export function lowerContextAccess(
   fn: HIRFunction,
-  loweredContextCallee: ExternalFunction,
+  loweredContextCalleeConfig: ExternalFunction,
 ): void {
   const contextAccess: Map<IdentifierId, CallExpression> = new Map();
   const contextKeys: Map<IdentifierId, Array<string>> = new Map();
@@ -79,6 +80,8 @@ export function lowerContextAccess(
     }
   }
 
+  let importLoweredContextCallee: NonLocalImportSpecifier | null = null;
+
   if (contextAccess.size > 0 && contextKeys.size > 0) {
     for (const [, block] of fn.body.blocks) {
       let nextInstructions: Array<Instruction> | null = null;
@@ -91,9 +94,13 @@ export function lowerContextAccess(
           isUseContextHookType(value.callee.identifier) &&
           contextKeys.has(lvalue.identifier.id)
         ) {
+          importLoweredContextCallee ??=
+            fn.env.programContext.addImportSpecifier(
+              loweredContextCalleeConfig,
+            );
           const loweredContextCalleeInstr = emitLoadLoweredContextCallee(
             fn.env,
-            loweredContextCallee,
+            importLoweredContextCallee,
           );
 
           if (nextInstructions === null) {
@@ -122,21 +129,16 @@ export function lowerContextAccess(
     }
     markInstructionIds(fn.body);
     inferTypes(fn);
-    fn.env.hasLoweredContextAccess = true;
   }
 }
 
 function emitLoadLoweredContextCallee(
   env: Environment,
-  loweredContextCallee: ExternalFunction,
+  importedLowerContextCallee: NonLocalImportSpecifier,
 ): Instruction {
   const loadGlobal: LoadGlobal = {
     kind: 'LoadGlobal',
-    binding: {
-      kind: 'ImportNamespace',
-      module: loweredContextCallee.source,
-      name: loweredContextCallee.importSpecifierName,
-    },
+    binding: {...importedLowerContextCallee},
     loc: GeneratedSource,
   };
 
@@ -144,6 +146,7 @@ function emitLoadLoweredContextCallee(
     id: makeInstructionId(0),
     loc: GeneratedSource,
     lvalue: createTemporaryPlace(env, GeneratedSource),
+    effects: null,
     value: loadGlobal,
   };
 }
@@ -190,6 +193,7 @@ function emitPropertyLoad(
     lvalue: object,
     value: loadObj,
     id: makeInstructionId(0),
+    effects: null,
     loc: GeneratedSource,
   };
 
@@ -204,6 +208,7 @@ function emitPropertyLoad(
     lvalue: element,
     value: loadProp,
     id: makeInstructionId(0),
+    effects: null,
     loc: GeneratedSource,
   };
   return {
@@ -235,6 +240,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
       kind: 'return',
       loc: GeneratedSource,
       value: arrayInstr.lvalue,
+      effects: null,
     },
     preds: new Set(),
     phis: new Set(),
@@ -248,6 +254,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
     params: [obj],
     returnTypeAnnotation: null,
     returnType: makeType(),
+    returns: createTemporaryPlace(env, GeneratedSource),
     context: [],
     effects: null,
     body: {
@@ -276,6 +283,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
       loc: GeneratedSource,
     },
     lvalue: createTemporaryPlace(env, GeneratedSource),
+    effects: null,
     loc: GeneratedSource,
   };
   return fnInstr;
@@ -292,6 +300,7 @@ function emitArrayInstr(elements: Array<Place>, env: Environment): Instruction {
     id: makeInstructionId(0),
     value: array,
     lvalue: arrayLvalue,
+    effects: null,
     loc: GeneratedSource,
   };
   return arrayInstr;

compiler/packages/babel-plugin-react-compiler/src/Optimization/OutlineJsx.ts

@@ -196,7 +196,7 @@ function process(
     return null;
   }
 
-  const props = collectProps(jsx);
+  const props = collectProps(fn.env, jsx);
   if (!props) return null;
 
   const outlinedTag = fn.env.generateGloballyUniqueIdentifierName(null).value;
@@ -217,6 +217,7 @@ type OutlinedJsxAttribute = {
 };
 
 function collectProps(
+  env: Environment,
   instructions: Array<JsxInstruction>,
 ): Array<OutlinedJsxAttribute> | null {
   let id = 1;
@@ -227,6 +228,7 @@ function collectProps(
       newName = `${oldName}${id++}`;
     }
     seen.add(newName);
+    env.programContext.addNewReference(newName);
     return newName;
   }
 
@@ -295,6 +297,7 @@ function emitOutlinedJsx(
       },
       loc: GeneratedSource,
     },
+    effects: null,
   };
   promoteTemporaryJsxTag(loadJsx.lvalue.identifier);
   const jsxExpr: Instruction = {
@@ -310,6 +313,7 @@ function emitOutlinedJsx(
       openingLoc: GeneratedSource,
       closingLoc: GeneratedSource,
     },
+    effects: null,
   };
 
   return [loadJsx, jsxExpr];
@@ -351,6 +355,7 @@ function emitOutlinedFn(
       kind: 'return',
       loc: GeneratedSource,
       value: instructions.at(-1)!.lvalue,
+      effects: null,
     },
     preds: new Set(),
     phis: new Set(),
@@ -364,6 +369,7 @@ function emitOutlinedFn(
     params: [propsObj],
     returnTypeAnnotation: null,
     returnType: makeType(),
+    returns: createTemporaryPlace(env, GeneratedSource),
     context: [],
     effects: null,
     body: {
@@ -515,6 +521,7 @@ function emitDestructureProps(
       loc: GeneratedSource,
       value: propsObj,
     },
+    effects: null,
   };
   return destructurePropsInstr;
 }

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts

@@ -14,7 +14,7 @@ import {
   renameVariables,
 } from '.';
 import {CompilerError, ErrorSeverity} from '../CompilerError';
-import {Environment, EnvironmentConfig, ExternalFunction} from '../HIR';
+import {Environment, ExternalFunction} from '../HIR';
 import {
   ArrayPattern,
   BlockId,
@@ -44,7 +44,7 @@ import {
   getHookKind,
   makeIdentifierName,
 } from '../HIR/HIR';
-import {printIdentifier, printPlace} from '../HIR/PrintHIR';
+import {printIdentifier, printInstruction, printPlace} from '../HIR/PrintHIR';
 import {eachPatternOperand} from '../HIR/visitors';
 import {Err, Ok, Result} from '../Utils/Result';
 import {GuardKind} from '../Utils/RuntimeDiagnosticConstants';
@@ -52,7 +52,8 @@ import {assertExhaustive} from '../Utils/utils';
 import {buildReactiveFunction} from './BuildReactiveFunction';
 import {SINGLE_CHILD_FBT_TAGS} from './MemoizeFbtAndMacroOperandsInSameScope';
 import {ReactiveFunctionVisitor, visitReactiveFunction} from './visitors';
-import {ReactFunctionType} from '../HIR/Environment';
+import {EMIT_FREEZE_GLOBAL_GATING, ReactFunctionType} from '../HIR/Environment';
+import {ProgramContext} from '../Entrypoint';
 
 export const MEMO_CACHE_SENTINEL = 'react.memo_cache_sentinel';
 export const EARLY_RETURN_SENTINEL = 'react.early_return_sentinel';
@@ -100,9 +101,10 @@ export type CodegenFunction = {
   }>;
 
   /**
-   * This is true if the compiler has the lowered useContext calls.
+   * This is true if the compiler has compiled inferred effect dependencies
    */
-  hasLoweredContextAccess: boolean;
+  hasInferredEffect: boolean;
+  inferredEffectLocations: Set<SourceLocation>;
 
   /**
    * This is true if the compiler has compiled a fire to a useFire call
@@ -156,10 +158,11 @@ export function codegenFunction(
   const compiled = compileResult.unwrap();
 
   const hookGuard = fn.env.config.enableEmitHookGuards;
-  if (hookGuard != null) {
+  if (hookGuard != null && fn.env.isInferredMemoEnabled) {
     compiled.body = t.blockStatement([
       createHookGuard(
         hookGuard,
+        fn.env.programContext,
         compiled.body.body,
         GuardKind.PushHookGuard,
         GuardKind.PopHookGuard,
@@ -170,13 +173,15 @@ export function codegenFunction(
   const cacheCount = compiled.memoSlotsUsed;
   if (cacheCount !== 0) {
     const preface: Array<t.Statement> = [];
+    const useMemoCacheIdentifier =
+      fn.env.programContext.addMemoCacheImport().name;
 
     // The import declaration for `useMemoCache` is inserted in the Babel plugin
     preface.push(
       t.variableDeclaration('const', [
         t.variableDeclarator(
           t.identifier(cx.synthesizeName('$')),
-          t.callExpression(t.identifier(fn.env.useMemoCacheIdentifier), [
+          t.callExpression(t.identifier(useMemoCacheIdentifier), [
             t.numericLiteral(cacheCount),
           ]),
         ),
@@ -250,39 +255,63 @@ export function codegenFunction(
   }
 
   const emitInstrumentForget = fn.env.config.enableEmitInstrumentForget;
-  if (emitInstrumentForget != null && fn.id != null) {
+  if (
+    emitInstrumentForget != null &&
+    fn.id != null &&
+    fn.env.isInferredMemoEnabled
+  ) {
     /*
      * Technically, this is a conditional hook call. However, we expect
      * __DEV__ and gating identifier to be runtime constants
      */
-    let gating: t.Expression;
-    if (
-      emitInstrumentForget.gating != null &&
+    const gating =
+      emitInstrumentForget.gating != null
+        ? t.identifier(
+            fn.env.programContext.addImportSpecifier(
+              emitInstrumentForget.gating,
+            ).name,
+          )
+        : null;
+
+    const globalGating =
       emitInstrumentForget.globalGating != null
-    ) {
-      gating = t.logicalExpression(
-        '&&',
-        t.identifier(emitInstrumentForget.globalGating),
-        t.identifier(emitInstrumentForget.gating.importSpecifierName),
+        ? t.identifier(emitInstrumentForget.globalGating)
+        : null;
+
+    if (emitInstrumentForget.globalGating != null) {
+      const assertResult = fn.env.programContext.assertGlobalBinding(
+        emitInstrumentForget.globalGating,
       );
-    } else if (emitInstrumentForget.gating != null) {
-      gating = t.identifier(emitInstrumentForget.gating.importSpecifierName);
+      if (assertResult.isErr()) {
+        return assertResult;
+      }
+    }
+
+    let ifTest: t.Expression;
+    if (gating != null && globalGating != null) {
+      ifTest = t.logicalExpression('&&', globalGating, gating);
+    } else if (gating != null) {
+      ifTest = gating;
     } else {
-      CompilerError.invariant(emitInstrumentForget.globalGating != null, {
+      CompilerError.invariant(globalGating != null, {
         reason:
           'Bad config not caught! Expected at least one of gating or globalGating',
         loc: null,
         suggestions: null,
       });
-      gating = t.identifier(emitInstrumentForget.globalGating);
+      ifTest = globalGating;
     }
+
+    const instrumentFnIdentifier = fn.env.programContext.addImportSpecifier(
+      emitInstrumentForget.fn,
+    ).name;
     const test: t.IfStatement = t.ifStatement(
-      gating,
+      ifTest,
       t.expressionStatement(
-        t.callExpression(
-          t.identifier(emitInstrumentForget.fn.importSpecifierName),
-          [t.stringLiteral(fn.id), t.stringLiteral(fn.env.filename ?? '')],
-        ),
+        t.callExpression(t.identifier(instrumentFnIdentifier), [
+          t.stringLiteral(fn.id),
+          t.stringLiteral(fn.env.filename ?? ''),
+        ]),
       ),
     );
     compiled.body.body.unshift(test);
@@ -359,8 +388,9 @@ function codegenReactiveFunction(
     prunedMemoBlocks: countMemoBlockVisitor.prunedMemoBlocks,
     prunedMemoValues: countMemoBlockVisitor.prunedMemoValues,
     outlined: [],
-    hasLoweredContextAccess: fn.env.hasLoweredContextAccess,
     hasFireRewrite: fn.env.hasFireRewrite,
+    hasInferredEffect: fn.env.hasInferredEffect,
+    inferredEffectLocations: fn.env.inferredEffectLocations,
   });
 }
 
@@ -548,14 +578,19 @@ function codegenBlockNoReset(
 }
 
 function wrapCacheDep(cx: Context, value: t.Expression): t.Expression {
-  if (cx.env.config.enableEmitFreeze != null) {
-    // The import declaration for emitFreeze is inserted in the Babel plugin
+  if (cx.env.config.enableEmitFreeze != null && cx.env.isInferredMemoEnabled) {
+    const emitFreezeIdentifier = cx.env.programContext.addImportSpecifier(
+      cx.env.config.enableEmitFreeze,
+    ).name;
+    cx.env.programContext
+      .assertGlobalBinding(EMIT_FREEZE_GLOBAL_GATING, cx.env.scope)
+      .unwrap();
     return t.conditionalExpression(
-      t.identifier('__DEV__'),
-      t.callExpression(
-        t.identifier(cx.env.config.enableEmitFreeze.importSpecifierName),
-        [value, t.stringLiteral(cx.fnName)],
-      ),
+      t.identifier(EMIT_FREEZE_GLOBAL_GATING),
+      t.callExpression(t.identifier(emitFreezeIdentifier), [
+        value,
+        t.stringLiteral(cx.fnName),
+      ]),
       value,
     );
   } else {
@@ -709,16 +744,14 @@ function codegenReactiveScope(
   let computationBlock = codegenBlock(cx, block);
 
   let memoStatement;
-  if (
-    cx.env.config.enableChangeDetectionForDebugging != null &&
-    changeExpressions.length > 0
-  ) {
+  const detectionFunction = cx.env.config.enableChangeDetectionForDebugging;
+  if (detectionFunction != null && changeExpressions.length > 0) {
     const loc =
       typeof scope.loc === 'symbol'
         ? 'unknown location'
         : `(${scope.loc.start.line}:${scope.loc.end.line})`;
-    const detectionFunction =
-      cx.env.config.enableChangeDetectionForDebugging.importSpecifierName;
+    const importedDetectionFunctionIdentifier =
+      cx.env.programContext.addImportSpecifier(detectionFunction).name;
     const cacheLoadOldValueStatements: Array<t.Statement> = [];
     const changeDetectionStatements: Array<t.Statement> = [];
     const idempotenceDetectionStatements: Array<t.Statement> = [];
@@ -740,7 +773,7 @@ function codegenReactiveScope(
       );
       changeDetectionStatements.push(
         t.expressionStatement(
-          t.callExpression(t.identifier(detectionFunction), [
+          t.callExpression(t.identifier(importedDetectionFunctionIdentifier), [
             t.identifier(loadName),
             t.cloneNode(name, true),
             t.stringLiteral(name.name),
@@ -752,7 +785,7 @@ function codegenReactiveScope(
       );
       idempotenceDetectionStatements.push(
         t.expressionStatement(
-          t.callExpression(t.identifier(detectionFunction), [
+          t.callExpression(t.identifier(importedDetectionFunctionIdentifier), [
             t.cloneNode(slot, true),
             t.cloneNode(name, true),
             t.stringLiteral(name.name),
@@ -967,6 +1000,14 @@ function codegenTerminal(
           lval = codegenLValue(cx, iterableItem.value.lvalue.pattern);
           break;
         }
+        case 'StoreContext': {
+          CompilerError.throwTodo({
+            reason: 'Support non-trivial for..in inits',
+            description: null,
+            loc: terminal.init.loc,
+            suggestions: null,
+          });
+        }
         default:
           CompilerError.invariant(false, {
             reason: `Expected a StoreLocal or Destructure to be assigned to the collection`,
@@ -1059,6 +1100,14 @@ function codegenTerminal(
           lval = codegenLValue(cx, iterableItem.value.lvalue.pattern);
           break;
         }
+        case 'StoreContext': {
+          CompilerError.throwTodo({
+            reason: 'Support non-trivial for..of inits',
+            description: null,
+            loc: terminal.init.loc,
+            suggestions: null,
+          });
+        }
         default:
           CompilerError.invariant(false, {
             reason: `Expected a StoreLocal or Destructure to be assigned to the collection`,
@@ -1261,7 +1310,7 @@ function codegenInstructionNullable(
         });
         CompilerError.invariant(value?.type === 'FunctionExpression', {
           reason: 'Expected a function as a function declaration value',
-          description: null,
+          description: `Got ${value == null ? String(value) : value.type} at ${printInstruction(instr)}`,
           loc: instr.value.loc,
           suggestions: null,
         });
@@ -1514,15 +1563,15 @@ const createStringLiteral = withLoc(t.stringLiteral);
 
 function createHookGuard(
   guard: ExternalFunction,
+  context: ProgramContext,
   stmts: Array<t.Statement>,
   before: GuardKind,
   after: GuardKind,
 ): t.TryStatement {
+  const guardFnName = context.addImportSpecifier(guard).name;
   function createHookGuardImpl(kind: number): t.ExpressionStatement {
     return t.expressionStatement(
-      t.callExpression(t.identifier(guard.importSpecifierName), [
-        t.numericLiteral(kind),
-      ]),
+      t.callExpression(t.identifier(guardFnName), [t.numericLiteral(kind)]),
     );
   }
 
@@ -1553,7 +1602,7 @@ function createHookGuard(
  * ```
  */
 function createCallExpression(
-  config: EnvironmentConfig,
+  env: Environment,
   callee: t.Expression,
   args: Array<t.Expression | t.SpreadElement>,
   loc: SourceLocation | null,
@@ -1564,14 +1613,15 @@ function createCallExpression(
     callExpr.loc = loc;
   }
 
-  const hookGuard = config.enableEmitHookGuards;
-  if (hookGuard != null && isHook) {
+  const hookGuard = env.config.enableEmitHookGuards;
+  if (hookGuard != null && isHook && env.isInferredMemoEnabled) {
     const iife = t.functionExpression(
       null,
       [],
       t.blockStatement([
         createHookGuard(
           hookGuard,
+          env.programContext,
           [t.returnStatement(callExpr)],
           GuardKind.AllowHook,
           GuardKind.DisallowHook,
@@ -1676,7 +1726,7 @@ function codegenInstructionValue(
     }
     case 'UnaryExpression': {
       value = t.unaryExpression(
-        instrValue.operator as 'throw', // todo
+        instrValue.operator,
         codegenPlaceToExpression(cx, instrValue.value),
       );
       break;
@@ -1701,7 +1751,7 @@ function codegenInstructionValue(
       const callee = codegenPlaceToExpression(cx, instrValue.callee);
       const args = instrValue.args.map(arg => codegenArgument(cx, arg));
       value = createCallExpression(
-        cx.env.config,
+        cx.env,
         callee,
         args,
         instrValue.loc,
@@ -1791,7 +1841,7 @@ function codegenInstructionValue(
       );
       const args = instrValue.args.map(arg => codegenArgument(cx, arg));
       value = createCallExpression(
-        cx.env.config,
+        cx.env,
         memberExpr,
         args,
         instrValue.loc,
@@ -2081,10 +2131,17 @@ function codegenInstructionValue(
     }
     case 'TypeCastExpression': {
       if (t.isTSType(instrValue.typeAnnotation)) {
-        value = t.tsAsExpression(
-          codegenPlaceToExpression(cx, instrValue.value),
-          instrValue.typeAnnotation,
-        );
+        if (instrValue.typeAnnotationKind === 'satisfies') {
+          value = t.tsSatisfiesExpression(
+            codegenPlaceToExpression(cx, instrValue.value),
+            instrValue.typeAnnotation,
+          );
+        } else {
+          value = t.tsAsExpression(
+            codegenPlaceToExpression(cx, instrValue.value),
+            instrValue.typeAnnotation,
+          );
+        }
       } else {
         value = t.typeCastExpression(
           codegenPlaceToExpression(cx, instrValue.value),
@@ -2270,9 +2327,12 @@ function codegenInstructionValue(
  * u0080 to u009F: C1 control codes
  * u00A0 to uFFFF: All non-basic Latin characters
  * https://en.wikipedia.org/wiki/List_of_Unicode_characters#Control_codes
+ *
+ * u010000 to u10FFFF: Astral plane characters
+ * https://mathiasbynens.be/notes/javascript-unicode
  */
 const STRING_REQUIRES_EXPR_CONTAINER_PATTERN =
-  /[\u{0000}-\u{001F}\u{007F}\u{0080}-\u{FFFF}]|"|\\/u;
+  /[\u{0000}-\u{001F}\u{007F}\u{0080}-\u{FFFF}\u{010000}-\u{10FFFF}]|"|\\/u;
 function codegenJsxAttribute(
   cx: Context,
   attribute: JsxAttribute,
@@ -2522,7 +2582,16 @@ function codegenValue(
   value: boolean | number | string | null | undefined,
 ): t.Expression {
   if (typeof value === 'number') {
-    return t.numericLiteral(value);
+    if (value < 0) {
+      /**
+       * Babel's code generator produces invalid JS for negative numbers when
+       * run with { compact: true }.
+       * See repro https://codesandbox.io/p/devbox/5d47fr
+       */
+      return t.unaryExpression('-', t.numericLiteral(-value), false);
+    } else {
+      return t.numericLiteral(value);
+    }
   } else if (typeof value === 'boolean') {
     return t.booleanLiteral(value);
   } else if (typeof value === 'string') {

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/MergeReactiveScopesThatInvalidateTogether.ts

@@ -456,6 +456,7 @@ function canMergeScopes(
       new Set(
         [...current.scope.declarations.values()].map(declaration => ({
           identifier: declaration.identifier,
+          reactive: true,
           path: [],
         })),
       ),

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PrintReactiveFunction.ts

@@ -255,6 +255,12 @@ function writeReactiveValue(writer: Writer, value: ReactiveValue): void {
   }
 }
 
+export function printReactiveTerminal(terminal: ReactiveTerminal): string {
+  const writer = new Writer();
+  writeTerminal(writer, terminal);
+  return writer.complete();
+}
+
 function writeTerminal(writer: Writer, terminal: ReactiveTerminal): void {
   switch (terminal.kind) {
     case 'break': {