[compiler][bugfix] expand StoreContext to const / let / function variants

```js
function Component() {
  useEffect(() => {
    let hasCleanedUp = false;
    document.addEventListener(..., () => hasCleanedUp ? foo() : bar());
    // effect return values shouldn't be typed as frozen
    return () => {
      hasCleanedUp = true;
    }
  };
}
```
### Problem
`PruneHoistedContexts` currently strips hoisted declarations and rewrites the first `StoreContext` reassignment to a declaration. For example, in the following example, instruction 0 is removed while a synthetic `DeclareContext let` is inserted before instruction 1.

```js
// source
const cb = () => x; // reference that causes x to be hoisted

let x = 4;
x = 5;

// React Compiler IR
[0] DeclareContext HoistedLet 'x'
...
[1] StoreContext reassign 'x' = 4
[2] StoreContext reassign 'x' = 5
```

Currently, we don't account for `DeclareContext let`. As a result, we're rewriting to insert duplicate declarations.
```js
// source
const cb = () => x; // reference that causes x to be hoisted

let x;
x = 5;

// React Compiler IR
[0] DeclareContext HoistedLet 'x'
...
[1] DeclareContext Let 'x'
[2] StoreContext reassign 'x' = 5
```

### Solution

Instead of always lowering context variables to a DeclareContext followed by a StoreContext reassign, we can keep `kind: 'Const' | 'Let' | 'Reassign' | etc` on StoreContext.
Pros:
- retain more information in HIR, so we can codegen easily `const` and `let` context variable declarations back
- pruning hoisted `DeclareContext` instructions is simple.

Cons:
- passes are more verbose as we need to check for both `DeclareContext` and `StoreContext` declarations

~(note: also see alternative implementation in https://github.com/facebook/react/pull/32745)~

### Testing
Context variables are tricky. I synced and diffed changes in a large meta codebase and feel pretty confident about landing this. About 0.01% of compiled files changed. Among these changes, ~25% were [direct bugfixes](https://www.internalfb.com/phabricator/paste/view/P1800029094). The [other changes](https://www.internalfb.com/phabricator/paste/view/P1800028575) were primarily due to changed (corrected) mutable ranges from https://github.com/facebook/react/pull/33047. I tried to represent most interesting changes in new test fixtures

`

.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

@@ -336,11 +336,11 @@ module.exports = {
         'packages/react-devtools-extensions/**/*.js',
         'packages/react-devtools-timeline/**/*.js',
         'packages/react-native-renderer/**/*.js',
+        'packages/eslint-plugin-react-hooks/**/*.js',
         'packages/jest-react/**/*.js',
         'packages/internal-test-utils/**/*.js',
         'packages/**/__tests__/*.js',
         'packages/**/npm/*.js',
-        'compiler/packages/eslint-plugin-react-hooks/**/*.js',
       ],
       rules: {
         'react-internal/prod-error-codes': OFF,
@@ -515,7 +515,7 @@ module.exports = {
       },
     },
     {
-      files: ['compiler/packages/eslint-plugin-react-hooks/src/**/*'],
+      files: ['packages/eslint-plugin-react-hooks/src/**/*'],
       extends: ['plugin:@typescript-eslint/recommended'],
       parser: '@typescript-eslint/parser',
       plugins: ['@typescript-eslint', 'eslint-plugin'],
@@ -615,6 +615,8 @@ module.exports = {
     GetAnimationsOptions: 'readonly',
     Animatable: 'readonly',
     ScrollTimeline: 'readonly',
+    EventListenerOptionsOrUseCapture: 'readonly',
+    FocusOptions: 'readonly',
 
     spyOnDev: 'readonly',
     spyOnDevAndProd: '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 +7,26 @@ on:
       - compiler/**
       - .github/workflows/compiler_**.yml
 
+permissions: {}
+
 jobs:
+  check_access:
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - 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
@@ -282,6 +313,9 @@ 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 }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -302,6 +336,7 @@ jobs:
         with:
           name: _build_${{ matrix.worker_id }}_${{ matrix.release_channel }}
           path: build
+          if-no-files-found: error
 
   test_build:
     name: yarn test-build
@@ -340,9 +375,16 @@ 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 +404,9 @@ 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 }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -381,6 +426,10 @@ jobs:
   process_artifacts_combined:
     name: Process artifacts combined
     needs: [build_and_lint, runtime_node_modules_cache]
+    permissions:
+      # https://github.com/actions/attest-build-provenance
+      id-token: write
+      attestations: write
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -398,6 +447,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ 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 +472,25 @@ 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 +512,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -484,6 +552,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ 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 +588,7 @@ 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 +632,26 @@ 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 +660,6 @@ 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 +671,13 @@ 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 +704,9 @@ jobs:
           path: |
             **/node_modules
           key: runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            runtime-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-node_modules-v6-
       - name: Ensure clean build directory
         run: rm -rf build
       - run: yarn install --frozen-lockfile
@@ -647,6 +728,7 @@ jobs:
         with:
           name: react-devtools-${{ matrix.browser }}-extension
           path: build/devtools/${{ matrix.browser }}-extension.zip
+          if-no-files-found: error
 
   merge_devtools_artifacts:
     name: Merge DevTools artifacts
@@ -679,6 +761,9 @@ 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 +785,10 @@ jobs:
   sizebot:
     if: ${{ github.event_name == 'pull_request' && github.ref_name != 'main' && github.event.pull_request.base.ref == 'main' }}
     name: Run sizebot
-    needs: [build_and_lint, runtime_node_modules_cache]
+    needs: [build_and_lint]
+    permissions:
+      # We use github.token to download the build artifact from a previous runtime_build_and_test.yml run
+      actions: read
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -712,7 +800,7 @@ jobs:
           cache: yarn
           cache-dependency-path: yarn.lock
       - name: Restore cached node_modules
-        uses: actions/cache/restore@v4
+        uses: actions/cache@v4 # note: this does not reuse centralized cache since it has unique cache key
         id: node_modules
         with:
           path: |
@@ -725,21 +813,23 @@ jobs:
       - run: yarn --cwd scripts/release install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
       - name: Download artifacts for base revision
+        # The build could have been generated from a fork, so we must download the build without
+        # any verification. This is safe since we only use this for sizebot calculation and the
+        # unverified artifact is not used. Additionally this workflow runs in the pull_request
+        # trigger so only restricted permissions are available.
         run: |
-          GH_TOKEN=${{ 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 +849,4 @@ 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
@@ -151,9 +173,9 @@ jobs:
           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 +192,20 @@ 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 +217,12 @@ 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 $CURRENT_VERSION_CLASSIC"
@@ -225,12 +252,12 @@ jobs:
             echo "should_commit=false" >> "$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 +271,8 @@ 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 +291,11 @@ 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 +308,10 @@ 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 $CURRENT_VERSION"
@@ -307,10 +337,10 @@ jobs:
             echo "should_commit=false" >> "$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 +7,26 @@ on:
       - compiler/**
       - .github/workflows/compiler_**.yml
 
+permissions: {}
+
 jobs:
+  check_access:
+    runs-on: ubuntu-latest
+    outputs:
+      is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}
+    steps:
+      - 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 +13,34 @@ 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
     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 +58,18 @@ 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: |
-          scripts/release/prepare-release-from-ci.js --skipTests -r ${{ inputs.release_channel }} --commit=${{ inputs.commit_sha }}
+          GH_TOKEN=${{ secrets.GH_TOKEN }} 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 }}
+      - 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

@@ -6,6 +6,8 @@ on:
       prerelease_commit_sha:
         required: true
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 
@@ -14,6 +16,9 @@ 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: ${{ inputs.prerelease_commit_sha }}
       release_channel: stable
@@ -30,10 +35,14 @@ jobs:
       dist_tag: canary,next
     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
@@ -45,3 +54,4 @@ jobs:
       dist_tag: experimental
     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 +14,25 @@ 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
     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 +42,8 @@ jobs:
       commit_sha: ${{ github.sha }}
       release_channel: experimental
       dist_tag: experimental
+      enableFailureNotification: true
     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 +12,23 @@ 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:
+      - 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 +36,11 @@ 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 +6,8 @@ on:
     - cron: '0 * * * *'
   workflow_dispatch:
 
+permissions: {}
+
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 

.nvmrc

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

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
@@ -33,6 +33,7 @@ const canaryChannelLabel = 'canary';
 const rcNumber = 0;
 
 const stablePackages = {
+  'eslint-plugin-react-hooks': '6.1.0',
   'jest-react': '0.17.0',
   react: ReactVersion,
   'react-art': ReactVersion,
@@ -41,12 +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

babel.config-react-compiler.js

@@ -0,0 +1,19 @@
+'use strict';
+
+/**
+ * HACK: @poteto React Compiler inlines Zod in its build artifact. Zod spreads values passed to .map
+ * which causes issues in @babel/plugin-transform-spread in loose mode, as it will result in
+ * {undefined: undefined} which fails to parse.
+ *
+ * [@babel/plugin-transform-block-scoping', {throwIfClosureRequired: true}] also causes issues with
+ * the built version of the compiler. The minimal set of plugins needed for this file is reexported
+ * from babel.config-ts.
+ *
+ * I will remove this hack later when we move eslint-plugin-react-hooks into the compiler directory.
+ **/
+
+const baseConfig = require('./babel.config-ts');
+
+module.exports = {
+  plugins: baseConfig.plugins,
+};

compiler/CHANGELOG.md

@@ -0,0 +1,59 @@
+## 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/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/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": "../../node_modules/eslint-v8/bin/eslint.js src",
-    "watch": "yarn build --watch"
+    "lint": "yarn eslint src",
+    "watch": "yarn build --dts --watch"
   },
   "dependencies": {
     "@babel/types": "^7.26.0"
@@ -43,7 +43,7 @@
     "babel-jest": "^29.0.3",
     "babel-plugin-fbt": "^1.0.0",
     "babel-plugin-fbt-runtime": "^1.0.0",
-    "eslint-v8": "npm:eslint@^8.57.1",
+    "eslint": "^8.57.1",
     "invariant": "^2.2.4",
     "jest": "^29.0.3",
     "jest-environment-jsdom": "^29.0.3",

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 +7,19 @@
 
 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 {CompilerReactTarget} from './Options';
+import {getReactCompilerRuntimeModule} from './Program';
 
 export function validateRestrictedImports(
   path: NodePath<t.Program>,
@@ -42,50 +52,209 @@ 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);
+export class ProgramContext {
+  /* Program and environment context */
+  scope: BabelScope;
+  reactRuntimeModule: string;
+  hookPattern: string | null;
 
-    const importSpecifierNameList = getOrInsertDefault(
-      sortedImports,
-      source,
-      [],
-    );
-    importSpecifierNameList.push(importSpecifierName);
+  // known generated or referenced identifiers in the program
+  knownReferencedNames: Set<string> = new Set();
+  // generated imports
+  imports: Map<string, Map<string, NonLocalImportSpecifier>> = new Map();
+
+  constructor(
+    program: NodePath<t.Program>,
+    reactRuntimeModule: CompilerReactTarget,
+    hookPattern: string | null,
+  ) {
+    this.hookPattern = hookPattern;
+    this.scope = program.scope;
+    this.reactRuntimeModule = getReactCompilerRuntimeModule(reactRuntimeModule);
   }
 
+  isHookName(name: string): boolean {
+    if (this.hookPattern == null) {
+      return isHookName(name);
+    } else {
+      const match = new RegExp(this.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);
+  }
+}
+
+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 +262,12 @@ 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 +275,3 @@ 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

@@ -182,7 +182,9 @@ export type LoggerEvent =
   | CompileDiagnosticEvent
   | CompileSkipEvent
   | PipelineErrorEvent
-  | TimingEvent;
+  | TimingEvent
+  | AutoDepsDecorationsEvent
+  | AutoDepsEligibleEvent;
 
 export type CompileErrorEvent = {
   kind: 'CompileError';
@@ -219,6 +221,16 @@ 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;

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 +100,9 @@ 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';
 
 export type CompilerPipelineValue =
   | {kind: 'ast'; name: string; value: CodegenFunction}
@@ -116,7 +117,7 @@ function run(
   config: EnvironmentConfig,
   fnType: ReactFunctionType,
   mode: CompilerMode,
-  useMemoCacheIdentifier: string,
+  programContext: ProgramContext,
   logger: Logger | null,
   filename: string | null,
   code: string | null,
@@ -131,7 +132,7 @@ function run(
     logger,
     filename,
     code,
-    useMemoCacheIdentifier,
+    programContext,
   );
   env.logger?.debugLogIRs?.({
     kind: 'debug',
@@ -161,7 +162,7 @@ function runWithEnvironment(
   log({kind: 'hir', name: 'PruneMaybeThrows', value: hir});
 
   validateContextVariableLValues(hir);
-  validateUseMemo(hir);
+  validateUseMemo(hir).unwrap();
 
   if (
     env.isInferredMemoEnabled &&
@@ -202,10 +203,10 @@ function runWithEnvironment(
 
   if (env.isInferredMemoEnabled) {
     if (env.config.validateHooksUsage) {
-      validateHooksUsage(hir);
+      validateHooksUsage(hir).unwrap();
     }
     if (env.config.validateNoCapitalizedCalls) {
-      validateNoCapitalizedCalls(hir);
+      validateNoCapitalizedCalls(hir).unwrap();
     }
   }
 
@@ -255,23 +256,23 @@ 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();
     }
   }
 
@@ -293,6 +294,10 @@ 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 +392,11 @@ function runWithEnvironment(
 
   if (env.config.inferEffectDependencies) {
     inferEffectDependencies(hir);
+    log({
+      kind: 'hir',
+      name: 'InferEffectDependencies',
+      value: hir,
+    });
   }
 
   if (env.config.inlineJsxTransform) {
@@ -509,14 +519,14 @@ 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 +557,7 @@ export function compileFn(
   config: EnvironmentConfig,
   fnType: ReactFunctionType,
   mode: CompilerMode,
-  useMemoCacheIdentifier: string,
+  programContext: ProgramContext,
   logger: Logger | null,
   filename: string | null,
   code: string | null,
@@ -557,7 +567,7 @@ export function compileFn(
     config,
     fnType,
     mode,
-    useMemoCacheIdentifier,
+    programContext,
     logger,
     filename,
     code,

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

@@ -12,11 +12,7 @@ import {
   CompilerErrorDetail,
   ErrorSeverity,
 } from '../CompilerError';
-import {
-  EnvironmentConfig,
-  ExternalFunction,
-  ReactFunctionType,
-} from '../HIR/Environment';
+import {EnvironmentConfig, ReactFunctionType} from '../HIR/Environment';
 import {CodegenFunction} from '../ReactiveScopes';
 import {isComponentDeclaration} from '../Utils/ComponentDeclaration';
 import {isHookDeclaration} from '../Utils/HookDeclaration';
@@ -24,16 +20,17 @@ import {assertExhaustive} from '../Utils/utils';
 import {insertGatedFunctionDeclaration} from './Gating';
 import {
   addImportsToProgram,
-  updateMemoCacheFunctionImport,
+  ProgramContext,
   validateRestrictedImports,
 } from './Imports';
-import {PluginOptions} from './Options';
+import {CompilerReactTarget, PluginOptions} from './Options';
 import {compileFn} from './Pipeline';
 import {
   filterSuppressionsThatAffectFunction,
   findProgramSuppressions,
   suppressionsToCompilerError,
 } from './Suppression';
+import {GeneratedSource} from '../HIR';
 
 export type CompilerPass = {
   opts: PluginOptions;
@@ -271,8 +268,9 @@ function isFilePartOfSources(
   return false;
 }
 
-type CompileProgramResult = {
+export type CompileProgramResult = {
   retryErrors: Array<{fn: BabelFn; error: CompilerError}>;
+  inferredEffectLocations: Set<t.SourceLocation>;
 };
 /**
  * `compileProgram` is directly invoked by the react-compiler babel plugin, so
@@ -299,8 +297,12 @@ export function compileProgram(
     handleError(restrictedImportsErr, pass, null);
     return null;
   }
-  const useMemoCacheIdentifier = program.scope.generateUidIdentifier('c');
 
+  const programContext = new ProgramContext(
+    program,
+    pass.opts.target,
+    environment.hookPattern,
+  );
   /*
    * Record lint errors and critical errors as depending on Forget's config,
    * we may still need to run Forget's analysis on every function (even if we
@@ -369,6 +371,7 @@ export function compileProgram(
     },
   );
   const retryErrors: Array<{fn: BabelFn; error: CompilerError}> = [];
+  const inferredEffectLocations = new Set<t.SourceLocation>();
   const processFn = (
     fn: BabelFn,
     fnType: ReactFunctionType,
@@ -410,7 +413,7 @@ export function compileProgram(
             environment,
             fnType,
             'all_features',
-            useMemoCacheIdentifier.name,
+            programContext,
             pass.opts.logger,
             pass.filename,
             pass.code,
@@ -445,12 +448,18 @@ export function compileProgram(
             environment,
             fnType,
             'no_inferred_memo',
-            useMemoCacheIdentifier.name,
+            programContext,
             pass.opts.logger,
             pass.filename,
             pass.code,
           ),
         };
+        if (
+          !compileResult.compiledFn.hasFireRewrite &&
+          !compileResult.compiledFn.hasInferredEffect
+        ) {
+          return null;
+        }
       } catch (err) {
         // TODO: we might want to log error here, but this will also result in duplicate logging
         if (err instanceof CompilerError) {
@@ -460,6 +469,23 @@ export function compileProgram(
       }
     }
 
+    /**
+     * Otherwise if 'use no forget/memo' is present, we still run the code through the compiler
+     * for validation but we don't mutate the babel AST. This allows us to flag if there is an
+     * unused 'use no forget/memo' directive.
+     */
+    if (pass.opts.ignoreUseNoForget === false && optOutDirectives.length > 0) {
+      for (const directive of optOutDirectives) {
+        pass.opts.logger?.logEvent(pass.filename, {
+          kind: 'CompileSkip',
+          fnLoc: fn.node.body.loc ?? null,
+          reason: `Skipped due to '${directive.value.value}' directive.`,
+          loc: directive.loc ?? null,
+        });
+      }
+      return null;
+    }
+
     pass.opts.logger?.logEvent(pass.filename, {
       kind: 'CompileSuccess',
       fnLoc: fn.node.loc ?? null,
@@ -483,26 +509,17 @@ export function compileProgram(
       return null;
     }
 
-    /**
-     * Otherwise if 'use no forget/memo' is present, we still run the code through the compiler
-     * for validation but we don't mutate the babel AST. This allows us to flag if there is an
-     * unused 'use no forget/memo' directive.
-     */
-    if (pass.opts.ignoreUseNoForget === false && optOutDirectives.length > 0) {
-      for (const directive of optOutDirectives) {
-        pass.opts.logger?.logEvent(pass.filename, {
-          kind: 'CompileSkip',
-          fnLoc: fn.node.body.loc ?? null,
-          reason: `Skipped due to '${directive.value.value}' directive.`,
-          loc: directive.loc ?? null,
-        });
-      }
-      return null;
-    }
-
     if (!pass.opts.noEmit) {
       return compileResult.compiledFn;
     }
+    /**
+     * inferEffectDependencies + noEmit is currently only used for linting. In
+     * this mode, add source locations for where the compiler *can* infer effect
+     * dependencies.
+     */
+    for (const loc of compileResult.compiledFn.inferredEffectLocations) {
+      if (loc !== GeneratedSource) inferredEffectLocations.add(loc);
+    }
     return null;
   };
 
@@ -548,79 +565,29 @@ export function compileProgram(
   if (moduleScopeOptOutDirectives.length > 0) {
     return null;
   }
-  let gating: null | {
-    gatingFn: ExternalFunction;
-    referencedBeforeDeclared: Set<CompileResult>;
-  } = null;
-  if (pass.opts.gating != null) {
-    gating = {
-      gatingFn: pass.opts.gating,
-      referencedBeforeDeclared:
-        getFunctionReferencedBeforeDeclarationAtTopLevel(program, compiledFns),
-    };
-  }
-
-  const hasLoweredContextAccess = compiledFns.some(
-    c => c.compiledFn.hasLoweredContextAccess,
-  );
-  const externalFunctions: Array<ExternalFunction> = [];
-  try {
-    // TODO: check for duplicate import specifiers
-    if (gating != null) {
-      externalFunctions.push(gating.gatingFn);
-    }
-
-    const lowerContextAccess = environment.lowerContextAccess;
-    if (lowerContextAccess && hasLoweredContextAccess) {
-      externalFunctions.push(lowerContextAccess);
-    }
-
-    const enableEmitInstrumentForget = environment.enableEmitInstrumentForget;
-    if (enableEmitInstrumentForget != null) {
-      externalFunctions.push(enableEmitInstrumentForget.fn);
-      if (enableEmitInstrumentForget.gating != null) {
-        externalFunctions.push(enableEmitInstrumentForget.gating);
-      }
-    }
-
-    if (environment.enableEmitFreeze != null) {
-      externalFunctions.push(environment.enableEmitFreeze);
-    }
-
-    if (environment.enableEmitHookGuards != null) {
-      externalFunctions.push(environment.enableEmitHookGuards);
-    }
-
-    if (environment.enableChangeDetectionForDebugging != null) {
-      externalFunctions.push(environment.enableChangeDetectionForDebugging);
-    }
-
-    const hasFireRewrite = compiledFns.some(c => c.compiledFn.hasFireRewrite);
-    if (environment.enableFire && hasFireRewrite) {
-      externalFunctions.push({
-        source: getReactCompilerRuntimeModule(pass.opts),
-        importSpecifierName: 'useFire',
-      });
-    }
-  } catch (err) {
-    handleError(err, pass, null);
-    return null;
-  }
-
   /*
    * Only insert Forget-ified functions if we have not encountered a critical
    * error elsewhere in the file, regardless of bailout mode.
    */
+  const referencedBeforeDeclared =
+    pass.opts.gating != null
+      ? getFunctionReferencedBeforeDeclarationAtTopLevel(program, compiledFns)
+      : null;
   for (const result of compiledFns) {
     const {kind, originalFn, compiledFn} = result;
     const transformedFn = createNewFunctionNode(originalFn, compiledFn);
 
-    if (gating != null && kind === 'original') {
+    if (referencedBeforeDeclared != null && kind === 'original') {
+      CompilerError.invariant(pass.opts.gating != null, {
+        reason: "Expected 'gating' import to be present",
+        loc: null,
+      });
       insertGatedFunctionDeclaration(
         originalFn,
         transformedFn,
-        gating.gatingFn,
-        gating.referencedBeforeDeclared.has(result),
+        programContext,
+        pass.opts.gating,
+        referencedBeforeDeclared.has(result),
       );
     } else {
       originalFn.replaceWith(transformedFn);
@@ -629,24 +596,9 @@ export function compileProgram(
 
   // Forget compiled the component, we need to update existing imports of useMemoCache
   if (compiledFns.length > 0) {
-    let needsMemoCacheFunctionImport = false;
-    for (const fn of compiledFns) {
-      if (fn.compiledFn.memoSlotsUsed > 0) {
-        needsMemoCacheFunctionImport = true;
-        break;
-      }
-    }
-
-    if (needsMemoCacheFunctionImport) {
-      updateMemoCacheFunctionImport(
-        program,
-        getReactCompilerRuntimeModule(pass.opts),
-        useMemoCacheIdentifier.name,
-      );
-    }
-    addImportsToProgram(program, externalFunctions);
+    addImportsToProgram(program, programContext);
   }
-  return {retryErrors};
+  return {retryErrors, inferredEffectLocations};
 }
 
 function shouldSkipCompilation(
@@ -677,7 +629,7 @@ function shouldSkipCompilation(
   if (
     hasMemoCacheFunctionImport(
       program,
-      getReactCompilerRuntimeModule(pass.opts),
+      getReactCompilerRuntimeModule(pass.opts.target),
     )
   ) {
     return true;
@@ -1002,31 +954,39 @@ function callsHooksOrCreatesJsx(
   return invokesHooks || createsJsx;
 }
 
+function isNonNode(node?: t.Expression | null): boolean {
+  if (!node) {
+    return true;
+  }
+  switch (node.type) {
+    case 'ObjectExpression':
+    case 'ArrowFunctionExpression':
+    case 'FunctionExpression':
+    case 'BigIntLiteral':
+    case 'ClassExpression':
+    case 'NewExpression': // technically `new Array()` is legit, but unlikely
+      return true;
+  }
+  return false;
+}
+
 function returnsNonNode(
   node: NodePath<
     t.FunctionDeclaration | t.ArrowFunctionExpression | t.FunctionExpression
   >,
 ): boolean {
-  let hasReturn = false;
   let returnsNonNode = false;
+  if (
+    // node.traverse#ArrowFunctionExpression isn't called for the root node
+    node.type === 'ArrowFunctionExpression' &&
+    node.node.body.type !== 'BlockStatement'
+  ) {
+    returnsNonNode = isNonNode(node.node.body);
+  }
 
   node.traverse({
     ReturnStatement(ret) {
-      hasReturn = true;
-      const argument = ret.node.argument;
-      if (argument == null) {
-        returnsNonNode = true;
-      } else {
-        switch (argument.type) {
-          case 'ObjectExpression':
-          case 'ArrowFunctionExpression':
-          case 'FunctionExpression':
-          case 'BigIntLiteral':
-          case 'ClassExpression':
-          case 'NewExpression': // technically `new Array()` is legit, but unlikely
-            returnsNonNode = true;
-        }
-      }
+      returnsNonNode = isNonNode(ret.node.argument);
     },
     // Skip traversing all nested functions and their return statements
     ArrowFunctionExpression: skipNestedFunctions(node),
@@ -1035,7 +995,7 @@ function returnsNonNode(
     ObjectMethod: node => node.skip(),
   });
 
-  return !hasReturn || returnsNonNode;
+  return returnsNonNode;
 }
 
 /*
@@ -1163,16 +1123,18 @@ function getFunctionReferencedBeforeDeclarationAtTopLevel(
   return referencedBeforeDeclaration;
 }
 
-function getReactCompilerRuntimeModule(opts: PluginOptions): string {
-  if (opts.target === '19') {
+export function getReactCompilerRuntimeModule(
+  target: CompilerReactTarget,
+): string {
+  if (target === '19') {
     return 'react/compiler-runtime'; // from react namespace
-  } else if (opts.target === '17' || opts.target === '18') {
+  } else if (target === '17' || target === '18') {
     return 'react-compiler-runtime'; // npm package
   } else {
     CompilerError.invariant(
-      opts.target != null &&
-        opts.target.kind === 'donotuse_meta_internal' &&
-        typeof opts.target.runtimeModule === 'string',
+      target != null &&
+        target.kind === 'donotuse_meta_internal' &&
+        typeof target.runtimeModule === 'string',
       {
         reason: 'Expected target to already be validated',
         description: null,
@@ -1180,6 +1142,6 @@ function getReactCompilerRuntimeModule(opts: PluginOptions): string {
         suggestions: null,
       },
     );
-    return opts.target.runtimeModule;
+    return target.runtimeModule;
   }
 }

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 {CompileProgramResult} 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: CompileProgramResult | 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: CompileProgramResult | 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/BuildHIR.ts

@@ -2406,6 +2406,19 @@ 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 +2430,7 @@ function lowerExpression(
         kind: 'TypeCastExpression',
         value: lowerExpressionToTemporary(builder, expr.get('expression')),
         typeAnnotation: typeAnnotation.node,
+        typeAnnotationKind: 'as',
         type: lowerType(typeAnnotation.node),
         loc: exprLoc,
       };
@@ -3595,31 +3609,40 @@ 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>;

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 {

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

@@ -11,10 +11,12 @@ import {fromZodError} from 'zod-validation-error';
 import {CompilerError} from '../CompilerError';
 import {
   CompilationMode,
+  defaultOptions,
   Logger,
   PanicThresholdOptions,
   parsePluginOptions,
   PluginOptions,
+  ProgramContext,
 } from '../Entrypoint';
 import {Err, Ok, Result} from '../Utils/Result';
 import {
@@ -84,6 +86,8 @@ 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')}),
@@ -330,6 +334,11 @@ 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,
@@ -771,6 +780,7 @@ export function parseConfigPragmaForTests(
   const environment = parseConfigPragmaEnvironmentForTest(pragma);
   let compilationMode: CompilationMode = defaults.compilationMode;
   let panicThreshold: PanicThresholdOptions = 'all_errors';
+  let noEmit: boolean = defaultOptions.noEmit;
   for (const token of pragma.split(' ')) {
     if (!token.startsWith('@')) {
       continue;
@@ -796,12 +806,17 @@ export function parseConfigPragmaForTests(
         panicThreshold = 'none';
         break;
       }
+      case '@noEmit': {
+        noEmit = true;
+        break;
+      }
     }
   }
   return parsePluginOptions({
     environment,
     compilationMode,
     panicThreshold,
+    noEmit,
   });
 }
 
@@ -841,9 +856,10 @@ 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>;
@@ -857,7 +873,7 @@ export class Environment {
     logger: Logger | null,
     filename: string | null,
     code: string | null,
-    useMemoCacheIdentifier: string,
+    programContext: ProgramContext,
   ) {
     this.#scope = scope;
     this.fnType = fnType;
@@ -866,11 +882,11 @@ 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 &&
@@ -932,6 +948,23 @@ 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

@@ -9,8 +9,12 @@ import {Effect, ValueKind, ValueReason} from './HIR';
 import {
   BUILTIN_SHAPES,
   BuiltInArrayId,
+  BuiltInFireFunctionId,
   BuiltInFireId,
+  BuiltInMapId,
   BuiltInMixedReadonlyId,
+  BuiltInObjectId,
+  BuiltInSetId,
   BuiltInUseActionStateId,
   BuiltInUseContextHookId,
   BuiltInUseEffectHookId,
@@ -45,29 +49,23 @@ 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 +73,8 @@ 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 +91,23 @@ 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 +139,7 @@ const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
         'from',
         addFunction(DEFAULT_SHAPES, [], {
           positionalParams: [
-            Effect.ConditionallyMutate,
+            Effect.ConditionallyMutateIterator,
             Effect.ConditionallyMutate,
             Effect.ConditionallyMutate,
           ],
@@ -372,6 +379,118 @@ 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,
+    ),
+  ],
   // TODO: rest of Global objects
 ];
 
@@ -556,7 +675,12 @@ 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,
       },

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

@@ -10,7 +10,7 @@ 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';
 
@@ -746,6 +746,27 @@ 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 +850,13 @@ 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 +901,20 @@ 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 +934,7 @@ export type InstructionValue =
       right: Place;
       loc: SourceLocation;
     }
-  | {
-      kind: 'NewExpression';
-      callee: Place;
-      args: Array<Place | SpreadPattern>;
-      loc: SourceLocation;
-    }
+  | NewExpression
   | CallExpression
   | MethodCall
   | {
@@ -908,13 +943,21 @@ 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 +1208,21 @@ 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
@@ -1394,6 +1440,7 @@ 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 +1459,11 @@ 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 +1477,7 @@ export function isMutableEffect(
     case Effect.Capture:
     case Effect.Store:
     case Effect.ConditionallyMutate:
+    case Effect.ConditionallyMutateIterator:
     case Effect.Mutate: {
       return true;
     }
@@ -1649,6 +1697,14 @@ 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';
 }
@@ -1699,6 +1755,12 @@ 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 isStableType(id: Identifier): boolean {
   return (
     isSetStateType(id) ||
@@ -1709,6 +1771,40 @@ 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

@@ -331,6 +331,7 @@ 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) {

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

@@ -44,6 +44,7 @@ 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 +55,7 @@ export function addFunction(
     kind: 'Function',
     return: fn.returnType,
     shapeId,
+    isConstructor,
   };
 }
 
@@ -73,6 +75,7 @@ export function addHook(
     kind: 'Function',
     return: fn.returnType,
     shapeId,
+    isConstructor: false,
   };
 }
 
@@ -198,6 +201,8 @@ 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 BuiltInFunctionId = 'BuiltInFunction';
 export const BuiltInJsxId = 'BuiltInJsx';
 export const BuiltInObjectId = 'BuiltInObject';
@@ -218,6 +223,7 @@ export const BuiltInUseContextHookId = 'BuiltInUseContextHook';
 export const BuiltInUseTransitionId = 'BuiltInUseTransition';
 export const BuiltInStartTransitionId = 'BuiltInStartTransition';
 export const BuiltInFireId = 'BuiltInFire';
+export const BuiltInFireFunctionId = 'BuiltInFireFunction';
 
 // ShapeRegistry with default definitions for built-ins.
 export const BUILTIN_SHAPES: ShapeRegistry = new Map();
@@ -451,6 +457,313 @@ 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,
+    }),
+  ],
+  [
+    /**
+     * 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, BuiltInUseStateId, [
   ['0', {kind: 'Poly'}],
   [

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;
 }
@@ -371,7 +385,7 @@ type Decl = {
   scope: Stack<ReactiveScope>;
 };
 
-class Context {
+export class DependencyCollectionContext {
   #declarations: Map<DeclarationId, Decl> = new Map();
   #reassignments: Map<Identifier, Decl> = new Map();
 
@@ -464,6 +478,9 @@ 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 {
@@ -638,7 +655,10 @@ 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 +682,21 @@ 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 +708,26 @@ 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 +741,7 @@ 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/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

@@ -32,5 +32,5 @@ 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/Inference/InferEffectDependencies.ts

@@ -1,3 +1,11 @@
+/**
+ * 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,
@@ -14,17 +22,30 @@ import {
   ScopeId,
   ReactiveScopeDependency,
   Place,
+  ReactiveScope,
   ReactiveScopeDependencies,
+  Terminal,
   isUseRefType,
   isSetStateType,
+  isFireFunctionType,
+  makeScopeId,
 } 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,
 } from '../HIR/HIRBuilder';
+import {
+  collectTemporariesSidemap,
+  DependencyCollectionContext,
+  handleInstruction,
+} from '../HIR/PropagateScopeDependenciesHIR';
 import {eachInstructionOperand, eachTerminalOperand} from '../HIR/visitors';
+import {empty} from '../Utils/Stack';
 import {getOrInsertWith} from '../Utils/utils';
 
 /**
@@ -53,10 +74,7 @@ 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>();
 
@@ -70,19 +88,18 @@ export function inferEffectDependencies(fn: HIRFunction): void {
   const reactiveIds = inferReactiveIdentifiers(fn);
 
   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>>();
     for (const instr of block.instructions) {
@@ -164,22 +181,12 @@ 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
              *
@@ -187,11 +194,14 @@ 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 dep of minimalDeps) {
               if (
-                (isUseRefType(dep.identifier) ||
+                ((isUseRefType(dep.identifier) ||
                   isSetStateType(dep.identifier)) &&
-                !reactiveIds.has(dep.identifier.id)
+                  !reactiveIds.has(dep.identifier.id)) ||
+                isFireFunctionType(dep.identifier)
               ) {
                 // exclude non-reactive hook results, which will never be in a memo block
                 continue;
@@ -205,6 +215,23 @@ export function inferEffectDependencies(fn: HIRFunction): void {
               );
               newInstructions.push(...instructions);
               effectDeps.push(place);
+              usedDeps.push(dep);
+            }
+
+            // 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,
+              });
             }
 
             newInstructions.push({
@@ -217,6 +244,7 @@ export function inferEffectDependencies(fn: HIRFunction): void {
             // 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);
+            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
             newInstructions.push({
@@ -227,6 +255,32 @@ export function inferEffectDependencies(fn: HIRFunction): void {
             });
             value.args.push({...depsPlace, effect: Effect.Freeze});
             rewriteInstrs.set(instr.id, newInstructions);
+            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,
+              },
+            });
           }
         }
       }
@@ -249,6 +303,7 @@ export function inferEffectDependencies(fn: HIRFunction): void {
     // Renumber instructions and fix scope ranges
     markInstructionIds(fn.body);
     fixScopeAndIdentifierRanges(fn.body);
+    fn.env.hasInferredEffect = true;
   }
 }
 
@@ -335,3 +390,163 @@ 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/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/InferReactivePlaces.ts

@@ -9,14 +9,19 @@ 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 {
@@ -31,6 +36,103 @@ 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 +213,7 @@ 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);
@@ -184,6 +287,7 @@ export function inferReactivePlaces(fn: HIRFunction): void {
         }
       }
       for (const instruction of block.instructions) {
+        stableIdentifierSources.handleInstruction(instruction);
         const {value} = instruction;
         let hasReactiveInput = false;
         /*
@@ -218,7 +322,13 @@ 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 +340,7 @@ 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);

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 {
@@ -38,7 +42,6 @@ import {
   printSourceLocation,
 } from '../HIR/PrintHIR';
 import {
-  eachCallArgument,
   eachInstructionOperand,
   eachInstructionValueOperand,
   eachPatternOperand,
@@ -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),
     );
@@ -879,9 +921,7 @@ 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 +944,12 @@ 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 +1247,12 @@ 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 +1270,12 @@ 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 +1611,14 @@ 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 +1690,13 @@ 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 +1737,7 @@ function inferBlock(
         state.referenceAndRecordEffects(
           freezeActions,
           instrValue.iterator,
-          Effect.ConditionallyMutate,
+          Effect.ConditionallyMutateIterator,
           ValueReason.Other,
         );
         /**
@@ -1926,8 +1809,15 @@ 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 +1873,7 @@ 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 +1902,33 @@ 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 +1940,20 @@ 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 +1964,10 @@ function areArgumentsImmutableAndNonMutating(
         break;
       }
       default: {
+        /**
+         * Globals, module locals, and other locally defined functions may
+         * mutate their arguments.
+         */
         return false;
       }
     }
@@ -2079,9 +2010,128 @@ 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/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,
   };
 

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;
   }
 

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,
@@ -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`,
@@ -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,
@@ -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),

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

@@ -6,12 +6,15 @@
  */
 
 import {
-  DeclarationId,
+  convertHoistedLValueKind,
+  IdentifierId,
   InstructionKind,
   ReactiveFunction,
   ReactiveInstruction,
+  ReactiveScopeBlock,
   ReactiveStatement,
 } from '../HIR';
+import {empty, Stack} from '../Utils/Stack';
 import {
   ReactiveFunctionTransform,
   Transformed,
@@ -23,76 +26,55 @@ import {
  * original instruction kind.
  */
 export function pruneHoistedContexts(fn: ReactiveFunction): void {
-  const hoistedIdentifiers: HoistedIdentifiers = new Map();
-  visitReactiveFunction(fn, new Visitor(), hoistedIdentifiers);
+  visitReactiveFunction(fn, new Visitor(), {
+    activeScopes: empty(),
+  });
 }
 
-type HoistedIdentifiers = Map<DeclarationId, InstructionKind>;
+type VisitorState = {
+  activeScopes: Stack<Set<IdentifierId>>;
+};
 
-class Visitor extends ReactiveFunctionTransform<HoistedIdentifiers> {
+class Visitor extends ReactiveFunctionTransform<VisitorState> {
+  override visitScope(scope: ReactiveScopeBlock, state: VisitorState): void {
+    state.activeScopes = state.activeScopes.push(
+      new Set(scope.scope.declarations.keys()),
+    );
+    this.traverseScope(scope, state);
+    state.activeScopes.pop();
+  }
   override transformInstruction(
     instruction: ReactiveInstruction,
-    state: HoistedIdentifiers,
+    state: VisitorState,
   ): Transformed<ReactiveStatement> {
     this.visitInstruction(instruction, state);
-    if (
-      instruction.value.kind === 'DeclareContext' &&
-      instruction.value.lvalue.kind === 'HoistedConst'
-    ) {
-      state.set(
-        instruction.value.lvalue.place.identifier.declarationId,
-        InstructionKind.Const,
-      );
-      return {kind: 'remove'};
-    }
 
-    if (
-      instruction.value.kind === 'DeclareContext' &&
-      instruction.value.lvalue.kind === 'HoistedLet'
-    ) {
-      state.set(
-        instruction.value.lvalue.place.identifier.declarationId,
-        InstructionKind.Let,
+    /**
+     * Remove hoisted declarations to preserve TDZ
+     */
+    if (instruction.value.kind === 'DeclareContext') {
+      const maybeNonHoisted = convertHoistedLValueKind(
+        instruction.value.lvalue.kind,
       );
-      return {kind: 'remove'};
+      if (maybeNonHoisted != null) {
+        return {kind: 'remove'};
+      }
     }
-
-    if (
-      instruction.value.kind === 'DeclareContext' &&
-      instruction.value.lvalue.kind === 'HoistedFunction'
-    ) {
-      state.set(
-        instruction.value.lvalue.place.identifier.declarationId,
-        InstructionKind.Function,
-      );
-      return {kind: 'remove'};
-    }
-
     if (
       instruction.value.kind === 'StoreContext' &&
-      state.has(instruction.value.lvalue.place.identifier.declarationId)
+      instruction.value.lvalue.kind !== InstructionKind.Reassign
     ) {
-      const kind = state.get(
-        instruction.value.lvalue.place.identifier.declarationId,
-      )!;
-      return {
-        kind: 'replace',
-        value: {
-          kind: 'instruction',
-          instruction: {
-            ...instruction,
-            value: {
-              ...instruction.value,
-              lvalue: {
-                ...instruction.value.lvalue,
-                kind,
-              },
-              type: null,
-              kind: 'StoreLocal',
-            },
-          },
-        },
-      };
+      /**
+       * Rewrite StoreContexts let/const/functions that will be pre-declared in
+       * codegen to reassignments.
+       */
+      const lvalueId = instruction.value.lvalue.place.identifier.id;
+      const isDeclaredByScope = state.activeScopes.find(scope =>
+        scope.has(lvalueId),
+      );
+      if (isDeclaredByScope) {
+        instruction.value.lvalue.kind = InstructionKind.Reassign;
+      }
     }
 
     return {kind: 'keep'};

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

@@ -5,6 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import {ProgramContext} from '..';
 import {CompilerError} from '../CompilerError';
 import {
   DeclarationId,
@@ -47,7 +48,7 @@ import {ReactiveFunctionVisitor, visitReactiveFunction} from './visitors';
  */
 export function renameVariables(fn: ReactiveFunction): Set<string> {
   const globals = collectReferencedGlobals(fn);
-  const scopes = new Scopes(globals);
+  const scopes = new Scopes(globals, fn.env.programContext);
   renameVariablesImpl(fn, new Visitor(), scopes);
   return new Set([...scopes.names, ...globals]);
 }
@@ -124,10 +125,12 @@ class Scopes {
   #seen: Map<DeclarationId, IdentifierName> = new Map();
   #stack: Array<Map<string, DeclarationId>> = [new Map()];
   #globals: Set<string>;
+  #programContext: ProgramContext;
   names: Set<ValidIdentifierName> = new Set();
 
-  constructor(globals: Set<string>) {
+  constructor(globals: Set<string>, programContext: ProgramContext) {
     this.#globals = globals;
+    this.#programContext = programContext;
   }
 
   visit(identifier: Identifier): void {
@@ -156,6 +159,7 @@ class Scopes {
         name = `${originalName.value}$${id++}`;
       }
     }
+    this.#programContext.addNewReference(name);
     const identifierName = makeIdentifierName(name);
     identifier.name = identifierName;
     this.#seen.set(identifier.declarationId, identifierName);

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/StabilizeBlockIds.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 {
   BlockId,
   ReactiveFunction,

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

@@ -14,7 +14,10 @@ export {extractScopeDeclarationsFromDestructuring} from './ExtractScopeDeclarati
 export {inferReactiveScopeVariables} from './InferReactiveScopeVariables';
 export {memoizeFbtAndMacroOperandsInSameScope} from './MemoizeFbtAndMacroOperandsInSameScope';
 export {mergeReactiveScopesThatInvalidateTogether} from './MergeReactiveScopesThatInvalidateTogether';
-export {printReactiveFunction} from './PrintReactiveFunction';
+export {
+  printReactiveFunction,
+  printReactiveFunctionWithOutlined,
+} from './PrintReactiveFunction';
 export {promoteUsedTemporaries} from './PromoteUsedTemporaries';
 export {propagateEarlyReturns} from './PropagateEarlyReturns';
 export {pruneAllReactiveScopes} from './PruneAllReactiveScopes';

compiler/packages/babel-plugin-react-compiler/src/Transform/TransformFire.ts

@@ -28,14 +28,20 @@ import {
   isUseEffectHookType,
   LoadLocal,
   makeInstructionId,
+  NonLocalImportSpecifier,
   Place,
   promoteTemporary,
 } from '../HIR';
 import {createTemporaryPlace, markInstructionIds} from '../HIR/HIRBuilder';
 import {getOrInsertWith} from '../Utils/utils';
-import {BuiltInFireId, DefaultNonmutatingHook} from '../HIR/ObjectShape';
+import {
+  BuiltInFireFunctionId,
+  BuiltInFireId,
+  DefaultNonmutatingHook,
+} from '../HIR/ObjectShape';
 import {eachInstructionOperand} from '../HIR/visitors';
 import {printSourceLocationLine} from '../HIR/PrintHIR';
+import {USE_FIRE_FUNCTION_NAME} from '../HIR/Environment';
 
 /*
  * TODO(jmbrown):
@@ -56,6 +62,7 @@ export function transformFire(fn: HIRFunction): void {
 }
 
 function replaceFireFunctions(fn: HIRFunction, context: Context): void {
+  let importedUseFire: NonLocalImportSpecifier | null = null;
   let hasRewrite = false;
   for (const [, block] of fn.body.blocks) {
     const rewriteInstrs = new Map<InstructionId, Array<Instruction>>();
@@ -87,7 +94,15 @@ function replaceFireFunctions(fn: HIRFunction, context: Context): void {
           ] of capturedCallees.entries()) {
             if (!context.hasCalleeWithInsertedFire(fireCalleePlace)) {
               context.addCalleeWithInsertedFire(fireCalleePlace);
-              const loadUseFireInstr = makeLoadUseFireInstruction(fn.env);
+
+              importedUseFire ??= fn.env.programContext.addImportSpecifier({
+                source: fn.env.programContext.reactRuntimeModule,
+                importSpecifierName: USE_FIRE_FUNCTION_NAME,
+              });
+              const loadUseFireInstr = makeLoadUseFireInstruction(
+                fn.env,
+                importedUseFire,
+              );
               const loadFireCalleeInstr = makeLoadFireCalleeInstruction(
                 fn.env,
                 fireCalleeInfo.capturedCalleeIdentifier,
@@ -404,18 +419,16 @@ function ensureNoMoreFireUses(fn: HIRFunction, context: Context): void {
   }
 }
 
-function makeLoadUseFireInstruction(env: Environment): Instruction {
+function makeLoadUseFireInstruction(
+  env: Environment,
+  importedLoadUseFire: NonLocalImportSpecifier,
+): Instruction {
   const useFirePlace = createTemporaryPlace(env, GeneratedSource);
   useFirePlace.effect = Effect.Read;
   useFirePlace.identifier.type = DefaultNonmutatingHook;
   const instrValue: InstructionValue = {
     kind: 'LoadGlobal',
-    binding: {
-      kind: 'ImportSpecifier',
-      name: 'useFire',
-      module: 'react',
-      imported: 'useFire',
-    },
+    binding: {...importedLoadUseFire},
     loc: GeneratedSource,
   };
   return {
@@ -624,6 +637,13 @@ class Context {
       () => createTemporaryPlace(this.#env, GeneratedSource),
     );
 
+    fireFunctionBinding.identifier.type = {
+      kind: 'Function',
+      shapeId: BuiltInFireFunctionId,
+      return: {kind: 'Poly'},
+      isConstructor: false,
+    };
+
     this.#capturedCalleeIdentifierIds.set(callee.identifier.id, {
       fireFunctionBinding,
       capturedCalleeIdentifier: callee.identifier,

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

@@ -4,4 +4,5 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
+
 export {transformFire} from './TransformFire';

compiler/packages/babel-plugin-react-compiler/src/TypeInference/InferTypes.ts

@@ -261,6 +261,7 @@ function* generateInstructionTypes(
         kind: 'Function',
         shapeId: null,
         return: returnType,
+        isConstructor: false,
       });
       yield equation(left, returnType);
       break;
@@ -277,6 +278,7 @@ function* generateInstructionTypes(
         kind: 'Function',
         shapeId: null,
         return: returnType,
+        isConstructor: false,
       });
       yield equation(left, returnType);
       break;
@@ -333,6 +335,7 @@ function* generateInstructionTypes(
         kind: 'Function',
         return: returnType,
         shapeId: null,
+        isConstructor: false,
       });
 
       yield equation(left, returnType);
@@ -405,6 +408,7 @@ function* generateInstructionTypes(
         kind: 'Function',
         shapeId: BuiltInFunctionId,
         return: value.loweredFunc.func.returnType,
+        isConstructor: false,
       });
       break;
     }
@@ -425,9 +429,20 @@ function* generateInstructionTypes(
       yield equation(left, {kind: 'Object', shapeId: BuiltInJsxId});
       break;
     }
+    case 'NewExpression': {
+      const returnType = makeType();
+      yield equation(value.callee.identifier.type, {
+        kind: 'Function',
+        return: returnType,
+        shapeId: null,
+        isConstructor: true,
+      });
+
+      yield equation(left, returnType);
+      break;
+    }
     case 'PropertyStore':
     case 'DeclareLocal':
-    case 'NewExpression':
     case 'RegExpLiteral':
     case 'MetaProperty':
     case 'ComputedStore':
@@ -505,7 +520,11 @@ class Unifier {
       return;
     }
 
-    if (tB.kind === 'Function' && tA.kind === 'Function') {
+    if (
+      tB.kind === 'Function' &&
+      tA.kind === 'Function' &&
+      tA.isConstructor === tB.isConstructor
+    ) {
       this.unify(tA.return, tB.return);
       return;
     }
@@ -648,6 +667,7 @@ class Unifier {
           kind: 'Function',
           return: returnType,
           shapeId: type.shapeId,
+          isConstructor: type.isConstructor,
         };
       }
       case 'ObjectMethod':

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateHooksUsage.ts

@@ -26,6 +26,7 @@ import {
   eachTerminalOperand,
 } from '../HIR/visitors';
 import {assertExhaustive} from '../Utils/utils';
+import {Result} from '../Utils/Result';
 
 /**
  * Represents the possible kinds of value which may be stored at a given Place during
@@ -87,7 +88,9 @@ function joinKinds(a: Kind, b: Kind): Kind {
  *   may not appear as the callee of a conditional call.
  *   See the note for Kind.PotentialHook for sources of potential hooks
  */
-export function validateHooksUsage(fn: HIRFunction): void {
+export function validateHooksUsage(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const unconditionalBlocks = computeUnconditionalBlocks(fn);
 
   const errors = new CompilerError();
@@ -423,9 +426,7 @@ export function validateHooksUsage(fn: HIRFunction): void {
   for (const [, error] of errorsByPlace) {
     errors.push(error);
   }
-  if (errors.hasErrors()) {
-    throw errors;
-  }
+  return errors.asResult();
 }
 
 function visitFunctionExpression(errors: CompilerError, fn: HIRFunction): void {

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateMemoizedEffectDependencies.ts

@@ -22,6 +22,7 @@ import {
   ReactiveFunctionVisitor,
   visitReactiveFunction,
 } from '../ReactiveScopes/visitors';
+import {Result} from '../Utils/Result';
 
 /**
  * Validates that all known effect dependencies are memoized. The algorithm checks two things:
@@ -47,12 +48,12 @@ import {
  * mutate(object); // ... mutable range ends here after this mutation
  * ```
  */
-export function validateMemoizedEffectDependencies(fn: ReactiveFunction): void {
+export function validateMemoizedEffectDependencies(
+  fn: ReactiveFunction,
+): Result<void, CompilerError> {
   const errors = new CompilerError();
   visitReactiveFunction(fn, new Visitor(), errors);
-  if (errors.hasErrors()) {
-    throw errors;
-  }
+  return errors.asResult();
 }
 
 class Visitor extends ReactiveFunctionVisitor<CompilerError> {

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoCapitalizedCalls.ts

@@ -4,11 +4,15 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
-import {CompilerError, EnvironmentConfig} from '..';
+
+import {CompilerError, EnvironmentConfig, ErrorSeverity} from '..';
 import {HIRFunction, IdentifierId} from '../HIR';
 import {DEFAULT_GLOBALS} from '../HIR/Globals';
+import {Result} from '../Utils/Result';
 
-export function validateNoCapitalizedCalls(fn: HIRFunction): void {
+export function validateNoCapitalizedCalls(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const envConfig: EnvironmentConfig = fn.env.config;
   const ALLOW_LIST = new Set([
     ...DEFAULT_GLOBALS.keys(),
@@ -26,6 +30,7 @@ export function validateNoCapitalizedCalls(fn: HIRFunction): void {
     );
   };
 
+  const errors = new CompilerError();
   const capitalLoadGlobals = new Map<IdentifierId, string>();
   const capitalizedProperties = new Map<IdentifierId, string>();
   const reason =
@@ -73,7 +78,8 @@ export function validateNoCapitalizedCalls(fn: HIRFunction): void {
           const propertyIdentifier = value.property.identifier.id;
           const propertyName = capitalizedProperties.get(propertyIdentifier);
           if (propertyName != null) {
-            CompilerError.throwInvalidReact({
+            errors.push({
+              severity: ErrorSeverity.InvalidReact,
               reason,
               description: `${propertyName} may be a component.`,
               loc: value.loc,
@@ -85,4 +91,5 @@ export function validateNoCapitalizedCalls(fn: HIRFunction): void {
       }
     }
   }
+  return errors.asResult();
 }

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoImpureFunctionsInRender.ts

@@ -8,6 +8,7 @@
 import {CompilerError, ErrorSeverity} from '..';
 import {HIRFunction} from '../HIR';
 import {getFunctionCallSignature} from '../Inference/InferReferenceEffects';
+import {Result} from '../Utils/Result';
 
 /**
  * Checks that known-impure functions are not called during render. Examples of invalid functions to
@@ -18,7 +19,9 @@ import {getFunctionCallSignature} from '../Inference/InferReferenceEffects';
  * this in several of our validation passes and should unify those analyses into a reusable helper
  * and use it here.
  */
-export function validateNoImpureFunctionsInRender(fn: HIRFunction): void {
+export function validateNoImpureFunctionsInRender(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const errors = new CompilerError();
   for (const [, block] of fn.body.blocks) {
     for (const instr of block.instructions) {
@@ -46,7 +49,5 @@ export function validateNoImpureFunctionsInRender(fn: HIRFunction): void {
       }
     }
   }
-  if (errors.hasErrors()) {
-    throw errors;
-  }
+  return errors.asResult();
 }

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoJSXInTryStatement.ts

@@ -7,6 +7,7 @@
 
 import {CompilerError, ErrorSeverity} from '..';
 import {BlockId, HIRFunction} from '../HIR';
+import {Result} from '../Utils/Result';
 import {retainWhere} from '../Utils/utils';
 
 /**
@@ -19,7 +20,9 @@ import {retainWhere} from '../Utils/utils';
  * created within a try block. JSX is allowed within a catch statement, unless that catch
  * is itself nested inside an outer try.
  */
-export function validateNoJSXInTryStatement(fn: HIRFunction): void {
+export function validateNoJSXInTryStatement(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const activeTryBlocks: Array<BlockId> = [];
   const errors = new CompilerError();
   for (const [, block] of fn.body.blocks) {
@@ -46,7 +49,5 @@ export function validateNoJSXInTryStatement(fn: HIRFunction): void {
       activeTryBlocks.push(block.terminal.handler);
     }
   }
-  if (errors.hasErrors()) {
-    throw errors;
-  }
+  return errors.asResult();
 }

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoRefAccesInRender.ts

@@ -99,9 +99,11 @@ class Env extends Map<IdentifierId, RefAccessType> {
   }
 }
 
-export function validateNoRefAccessInRender(fn: HIRFunction): void {
+export function validateNoRefAccessInRender(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const env = new Env();
-  validateNoRefAccessInRenderImpl(fn, env).unwrap();
+  return validateNoRefAccessInRenderImpl(fn, env).map(_ => undefined);
 }
 
 function refTypeOfType(place: Place): RefAccessType {

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoSetStateInPassiveEffects.ts

@@ -14,6 +14,7 @@ import {
   Place,
 } from '../HIR';
 import {eachInstructionValueOperand} from '../HIR/visitors';
+import {Result} from '../Utils/Result';
 
 /**
  * Validates against calling setState in the body of a *passive* effect (useEffect),
@@ -23,7 +24,9 @@ import {eachInstructionValueOperand} from '../HIR/visitors';
  * often bad for performance and frequently has more efficient and straightforward
  * alternatives. See https://react.dev/learn/you-might-not-need-an-effect for examples.
  */
-export function validateNoSetStateInPassiveEffects(fn: HIRFunction): void {
+export function validateNoSetStateInPassiveEffects(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const setStateFunctions: Map<IdentifierId, Place> = new Map();
   const errors = new CompilerError();
   for (const [, block] of fn.body.blocks) {
@@ -98,9 +101,7 @@ export function validateNoSetStateInPassiveEffects(fn: HIRFunction): void {
     }
   }
 
-  if (errors.hasErrors()) {
-    throw errors;
-  }
+  return errors.asResult();
 }
 
 function getSetStateCall(

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateNoSetStateInRender.ts

@@ -9,7 +9,7 @@ import {CompilerError, ErrorSeverity} from '../CompilerError';
 import {HIRFunction, IdentifierId, isSetStateType} from '../HIR';
 import {computeUnconditionalBlocks} from '../HIR/ComputeUnconditionalBlocks';
 import {eachInstructionValueOperand} from '../HIR/visitors';
-import {Err, Ok, Result} from '../Utils/Result';
+import {Result} from '../Utils/Result';
 
 /**
  * Validates that the given function does not have an infinite update loop
@@ -39,9 +39,11 @@ import {Err, Ok, Result} from '../Utils/Result';
  * y();
  * ```
  */
-export function validateNoSetStateInRender(fn: HIRFunction): void {
+export function validateNoSetStateInRender(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
   const unconditionalSetStateFunctions: Set<IdentifierId> = new Set();
-  validateNoSetStateInRenderImpl(fn, unconditionalSetStateFunctions).unwrap();
+  return validateNoSetStateInRenderImpl(fn, unconditionalSetStateFunctions);
 }
 
 function validateNoSetStateInRenderImpl(
@@ -145,9 +147,5 @@ function validateNoSetStateInRenderImpl(
     }
   }
 
-  if (errors.hasErrors()) {
-    return Err(errors);
-  } else {
-    return Ok(undefined);
-  }
+  return errors.asResult();
 }

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidatePreservedManualMemoization.ts

@@ -5,9 +5,10 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {CompilerError, Effect, ErrorSeverity} from '..';
+import {CompilerError, ErrorSeverity} from '../CompilerError';
 import {
   DeclarationId,
+  Effect,
   GeneratedSource,
   Identifier,
   IdentifierId,
@@ -30,6 +31,7 @@ import {
   ReactiveFunctionVisitor,
   visitReactiveFunction,
 } from '../ReactiveScopes/visitors';
+import {Result} from '../Utils/Result';
 import {getOrInsertDefault} from '../Utils/utils';
 
 /**
@@ -39,15 +41,15 @@ import {getOrInsertDefault} from '../Utils/utils';
  * This can occur if a value's mutable range somehow extended to include a hook and
  * was pruned.
  */
-export function validatePreservedManualMemoization(fn: ReactiveFunction): void {
+export function validatePreservedManualMemoization(
+  fn: ReactiveFunction,
+): Result<void, CompilerError> {
   const state = {
     errors: new CompilerError(),
     manualMemoState: null,
   };
   visitReactiveFunction(fn, new Visitor(), state);
-  if (state.errors.hasErrors()) {
-    throw state.errors;
-  }
+  return state.errors.asResult();
 }
 
 const DEBUG = false;

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateStaticComponents.ts

@@ -0,0 +1,83 @@
+/**
+ * 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, ErrorSeverity} from '../CompilerError';
+import {HIRFunction, IdentifierId, SourceLocation} from '../HIR';
+import {Result} from '../Utils/Result';
+
+/**
+ * Validates against components that are created dynamically and whose identity is not guaranteed
+ * to be stable (which would cause the component to reset on each re-render).
+ */
+export function validateStaticComponents(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
+  const error = new CompilerError();
+  const knownDynamicComponents = new Map<IdentifierId, SourceLocation>();
+  for (const block of fn.body.blocks.values()) {
+    phis: for (const phi of block.phis) {
+      for (const operand of phi.operands.values()) {
+        const loc = knownDynamicComponents.get(operand.identifier.id);
+        if (loc != null) {
+          knownDynamicComponents.set(phi.place.identifier.id, loc);
+          continue phis;
+        }
+      }
+    }
+    for (const instr of block.instructions) {
+      const {lvalue, value} = instr;
+      switch (value.kind) {
+        case 'FunctionExpression':
+        case 'NewExpression':
+        case 'MethodCall':
+        case 'CallExpression': {
+          knownDynamicComponents.set(lvalue.identifier.id, value.loc);
+          break;
+        }
+        case 'LoadLocal': {
+          const loc = knownDynamicComponents.get(value.place.identifier.id);
+          if (loc != null) {
+            knownDynamicComponents.set(lvalue.identifier.id, loc);
+          }
+          break;
+        }
+        case 'StoreLocal': {
+          const loc = knownDynamicComponents.get(value.value.identifier.id);
+          if (loc != null) {
+            knownDynamicComponents.set(lvalue.identifier.id, loc);
+            knownDynamicComponents.set(value.lvalue.place.identifier.id, loc);
+          }
+          break;
+        }
+        case 'JsxExpression': {
+          if (value.tag.kind === 'Identifier') {
+            const location = knownDynamicComponents.get(
+              value.tag.identifier.id,
+            );
+            if (location != null) {
+              error.push({
+                reason: `Components created during render will reset their state each time they are created. Declare components outside of render. `,
+                severity: ErrorSeverity.InvalidReact,
+                loc: value.tag.loc,
+                description: null,
+                suggestions: null,
+              });
+              error.push({
+                reason: `The component may be created during render`,
+                severity: ErrorSeverity.InvalidReact,
+                loc: location,
+                description: null,
+                suggestions: null,
+              });
+            }
+          }
+        }
+      }
+    }
+  }
+  return error.asResult();
+}

compiler/packages/babel-plugin-react-compiler/src/Validation/ValidateUseMemo.ts

@@ -5,10 +5,12 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {CompilerError} from '..';
+import {CompilerError, ErrorSeverity} from '..';
 import {FunctionExpression, HIRFunction, IdentifierId} from '../HIR';
+import {Result} from '../Utils/Result';
 
-export function validateUseMemo(fn: HIRFunction): void {
+export function validateUseMemo(fn: HIRFunction): Result<void, CompilerError> {
+  const errors = new CompilerError();
   const useMemos = new Set<IdentifierId>();
   const react = new Set<IdentifierId>();
   const functions = new Map<IdentifierId, FunctionExpression>();
@@ -61,7 +63,8 @@ export function validateUseMemo(fn: HIRFunction): void {
           }
 
           if (body.loweredFunc.func.params.length > 0) {
-            CompilerError.throwInvalidReact({
+            errors.push({
+              severity: ErrorSeverity.InvalidReact,
               reason: 'useMemo callbacks may not accept any arguments',
               description: null,
               loc: body.loc,
@@ -70,7 +73,8 @@ export function validateUseMemo(fn: HIRFunction): void {
           }
 
           if (body.loweredFunc.func.async || body.loweredFunc.func.generator) {
-            CompilerError.throwInvalidReact({
+            errors.push({
+              severity: ErrorSeverity.InvalidReact,
               reason:
                 'useMemo callbacks may not be async or generator functions',
               description: null,
@@ -84,4 +88,5 @@ export function validateUseMemo(fn: HIRFunction): void {
       }
     }
   }
+  return errors.asResult();
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/e2e/constant-prop.e2e.js

@@ -12,6 +12,7 @@ globalThis.constantValue = 'global test value';
 
 test('literal-constant-propagation', () => {
   function Component() {
+    'use memo';
     const x = 'test value 1';
     return <div>{x}</div>;
   }
@@ -38,6 +39,7 @@ test('literal-constant-propagation', () => {
 
 test('global-constant-propagation', () => {
   function Component() {
+    'use memo';
     const x = constantValue;
 
     return <div>{x}</div>;
@@ -65,6 +67,7 @@ test('global-constant-propagation', () => {
 
 test('lambda-constant-propagation', () => {
   function Component() {
+    'use memo';
     const x = 'test value 1';
     const getDiv = () => <div>{x}</div>;
     return getDiv();
@@ -92,6 +95,7 @@ test('lambda-constant-propagation', () => {
 
 test('lambda-constant-propagation-of-phi-node', () => {
   function Component({noopCallback}) {
+    'use memo';
     const x = 'test value 1';
     if (constantValue) {
       noopCallback();

compiler/packages/babel-plugin-react-compiler/src/__tests__/e2e/update-button.e2e.js

@@ -16,6 +16,7 @@ function Button({label}) {
 
 let currentTheme = 'light';
 function useTheme() {
+  'use memo';
   return currentTheme;
 }
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/e2e/update-expressions.e2e.js

@@ -10,6 +10,7 @@ import * as React from 'react';
 import {expectLogsAndClear, log} from './expectLogs';
 
 function Counter(props) {
+  'use memo';
   let value = props.value;
   let a = value++;
   expect(a).toBe(props.value); // postfix

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/array-from-arg1-captures-arg0.expect.md

@@ -50,28 +50,55 @@ import { useIdentity, Stringify } from "shared-runtime";
  * (2) the 1st argument might mutate its callee
  */
 function Component(t0) {
-  const $ = _c(4);
+  const $ = _c(10);
   const { value } = t0;
-  const arr = [{ value: "foo" }, { value: "bar" }, { value }];
-  useIdentity();
-  const derived = Array.from(arr, _temp);
   let t1;
-  if ($[0] !== derived) {
-    t1 = derived.at(-1);
-    $[0] = derived;
-    $[1] = t1;
-  } else {
-    t1 = $[1];
-  }
   let t2;
-  if ($[2] !== t1) {
-    t2 = <Stringify>{t1}</Stringify>;
-    $[2] = t1;
-    $[3] = t2;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t1 = { value: "foo" };
+    t2 = { value: "bar" };
+    $[0] = t1;
+    $[1] = t2;
   } else {
-    t2 = $[3];
+    t1 = $[0];
+    t2 = $[1];
   }
-  return t2;
+  let t3;
+  if ($[2] !== value) {
+    t3 = [t1, t2, { value }];
+    $[2] = value;
+    $[3] = t3;
+  } else {
+    t3 = $[3];
+  }
+  const arr = t3;
+  useIdentity();
+  let t4;
+  if ($[4] !== arr) {
+    t4 = Array.from(arr, _temp);
+    $[4] = arr;
+    $[5] = t4;
+  } else {
+    t4 = $[5];
+  }
+  const derived = t4;
+  let t5;
+  if ($[6] !== derived) {
+    t5 = derived.at(-1);
+    $[6] = derived;
+    $[7] = t5;
+  } else {
+    t5 = $[7];
+  }
+  let t6;
+  if ($[8] !== t5) {
+    t6 = <Stringify>{t5}</Stringify>;
+    $[8] = t5;
+    $[9] = t6;
+  } else {
+    t6 = $[9];
+  }
+  return t6;
 }
 function _temp(x, idx) {
   return { ...x, id: idx };

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/array-from-captures-arg0.expect.md

@@ -50,28 +50,55 @@ import { useIdentity, Stringify } from "shared-runtime";
  * (2) the 1st argument might mutate its callee
  */
 function Component(t0) {
-  const $ = _c(4);
+  const $ = _c(10);
   const { value } = t0;
-  const arr = [{ value: "foo" }, { value: "bar" }, { value }];
-  useIdentity();
-  const derived = Array.from(arr);
   let t1;
-  if ($[0] !== derived) {
-    t1 = derived.at(-1);
-    $[0] = derived;
-    $[1] = t1;
-  } else {
-    t1 = $[1];
-  }
   let t2;
-  if ($[2] !== t1) {
-    t2 = <Stringify>{t1}</Stringify>;
-    $[2] = t1;
-    $[3] = t2;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t1 = { value: "foo" };
+    t2 = { value: "bar" };
+    $[0] = t1;
+    $[1] = t2;
   } else {
-    t2 = $[3];
+    t1 = $[0];
+    t2 = $[1];
   }
-  return t2;
+  let t3;
+  if ($[2] !== value) {
+    t3 = [t1, t2, { value }];
+    $[2] = value;
+    $[3] = t3;
+  } else {
+    t3 = $[3];
+  }
+  const arr = t3;
+  useIdentity();
+  let t4;
+  if ($[4] !== arr) {
+    t4 = Array.from(arr);
+    $[4] = arr;
+    $[5] = t4;
+  } else {
+    t4 = $[5];
+  }
+  const derived = t4;
+  let t5;
+  if ($[6] !== derived) {
+    t5 = derived.at(-1);
+    $[6] = derived;
+    $[7] = t5;
+  } else {
+    t5 = $[7];
+  }
+  let t6;
+  if ($[8] !== t5) {
+    t6 = <Stringify>{t5}</Stringify>;
+    $[8] = t5;
+    $[9] = t6;
+  } else {
+    t6 = $[9];
+  }
+  return t6;
 }
 
 export const FIXTURE_ENTRYPOINT = {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/array-from-maybemutates-arg0.expect.md

@@ -7,14 +7,19 @@ import {mutateAndReturn, Stringify, useIdentity} from 'shared-runtime';
 function Component({value}) {
   const arr = [{value: 'foo'}, {value: 'bar'}, {value}];
   useIdentity();
-  const derived = Array.from(arr, mutateAndReturn);
-  return <Stringify>{derived.at(-1)}</Stringify>;
+  const derived = Array.from(arr).map(mutateAndReturn);
+  return (
+    <Stringify>
+      {derived.at(0)}
+      {derived.at(-1)}
+    </Stringify>
+  );
 }
 
 export const FIXTURE_ENTRYPOINT = {
   fn: Component,
   params: [{value: 5}],
-  sequentialRenders: [{value: 5}, {value: 6}, {value: 6}],
+  sequentialRenders: [{value: 5}, {value: 6}, {value: 6}, {value: 7}],
 };
 
 ```
@@ -26,39 +31,54 @@ import { c as _c } from "react/compiler-runtime";
 import { mutateAndReturn, Stringify, useIdentity } from "shared-runtime";
 
 function Component(t0) {
-  const $ = _c(4);
+  const $ = _c(7);
   const { value } = t0;
   const arr = [{ value: "foo" }, { value: "bar" }, { value }];
   useIdentity();
-  const derived = Array.from(arr, mutateAndReturn);
+  const derived = Array.from(arr).map(mutateAndReturn);
   let t1;
   if ($[0] !== derived) {
-    t1 = derived.at(-1);
+    t1 = derived.at(0);
     $[0] = derived;
     $[1] = t1;
   } else {
     t1 = $[1];
   }
   let t2;
-  if ($[2] !== t1) {
-    t2 = <Stringify>{t1}</Stringify>;
-    $[2] = t1;
+  if ($[2] !== derived) {
+    t2 = derived.at(-1);
+    $[2] = derived;
     $[3] = t2;
   } else {
     t2 = $[3];
   }
-  return t2;
+  let t3;
+  if ($[4] !== t1 || $[5] !== t2) {
+    t3 = (
+      <Stringify>
+        {t1}
+        {t2}
+      </Stringify>
+    );
+    $[4] = t1;
+    $[5] = t2;
+    $[6] = t3;
+  } else {
+    t3 = $[6];
+  }
+  return t3;
 }
 
 export const FIXTURE_ENTRYPOINT = {
   fn: Component,
   params: [{ value: 5 }],
-  sequentialRenders: [{ value: 5 }, { value: 6 }, { value: 6 }],
+  sequentialRenders: [{ value: 5 }, { value: 6 }, { value: 6 }, { value: 7 }],
 };
 
 ```
       
 ### Eval output
-(kind: ok) <div>{"children":{"value":5,"wat0":"joe"}}</div>
-<div>{"children":{"value":6,"wat0":"joe"}}</div>
-<div>{"children":{"value":6,"wat0":"joe"}}</div>
+(kind: ok) <div>{"children":[{"value":"foo","wat0":"joe"},{"value":5,"wat0":"joe"}]}</div>
+<div>{"children":[{"value":"foo","wat0":"joe"},{"value":6,"wat0":"joe"}]}</div>
+<div>{"children":[{"value":"foo","wat0":"joe"},{"value":6,"wat0":"joe"}]}</div>
+<div>{"children":[{"value":"foo","wat0":"joe"},{"value":7,"wat0":"joe"}]}</div>

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/array-from-maybemutates-arg0.js

@@ -3,12 +3,17 @@ import {mutateAndReturn, Stringify, useIdentity} from 'shared-runtime';
 function Component({value}) {
   const arr = [{value: 'foo'}, {value: 'bar'}, {value}];
   useIdentity();
-  const derived = Array.from(arr, mutateAndReturn);
-  return <Stringify>{derived.at(-1)}</Stringify>;
+  const derived = Array.from(arr).map(mutateAndReturn);
+  return (
+    <Stringify>
+      {derived.at(0)}
+      {derived.at(-1)}
+    </Stringify>
+  );
 }
 
 export const FIXTURE_ENTRYPOINT = {
   fn: Component,
   params: [{value: 5}],
-  sequentialRenders: [{value: 5}, {value: 6}, {value: 6}],
+  sequentialRenders: [{value: 5}, {value: 6}, {value: 6}, {value: 7}],
 };