[compiler] Alternate take on ref validation

Some of the false positives we've seen have to do with the need to align our ref validation with our understanding of which functions may be called during render. The new mutability/aliasing model makes this much more explicit, with the ability to create Impure effects which we then throw as errors if they are reachable during render. This means we can now revisit ref validation by just emitting impure effects.

That's what this new pass does. It's a bit simpler: it implements the check for `ref.current == null` guarded if blocks. Otherwise it disallows access to `ref.current` specifically. Unlike before, we intentionally allow passing ref objects to functions — we just see a lot of many false positives on disallowing things like `children({ref})` or similar.

Open to feedback! This is also still WIP.

.eslintrc.js

@@ -496,6 +496,7 @@ module.exports = {
         'packages/react-devtools-shared/src/devtools/views/**/*.js',
         'packages/react-devtools-shared/src/hook.js',
         'packages/react-devtools-shared/src/backend/console.js',
+        'packages/react-devtools-shared/src/backend/fiber/renderer.js',
         'packages/react-devtools-shared/src/backend/shared/DevToolsComponentStackFrame.js',
         'packages/react-devtools-shared/src/frontend/utils/withPermissionsCheck.js',
       ],
@@ -504,6 +505,7 @@ module.exports = {
         __IS_FIREFOX__: 'readonly',
         __IS_EDGE__: 'readonly',
         __IS_NATIVE__: 'readonly',
+        __IS_INTERNAL_MCP_BUILD__: 'readonly',
         __IS_INTERNAL_VERSION__: 'readonly',
         chrome: 'readonly',
       },
@@ -559,6 +561,7 @@ module.exports = {
     ConsoleTask: 'readonly', // TOOD: Figure out what the official name of this will be.
     ReturnType: 'readonly',
     AnimationFrameID: 'readonly',
+    WeakRef: 'readonly',
     // For Flow type annotation. Only `BigInt` is valid at runtime.
     bigint: 'readonly',
     BigInt: 'readonly',
@@ -609,6 +612,7 @@ module.exports = {
     TimeoutID: 'readonly',
     WheelEventHandler: 'readonly',
     FinalizationRegistry: 'readonly',
+    Exclude: 'readonly',
     Omit: 'readonly',
     Keyframe: 'readonly',
     PropertyIndexedKeyframes: 'readonly',

.github/workflows/compiler_discord_notify.yml

@@ -11,6 +11,7 @@ permissions: {}
 
 jobs:
   check_access:
+    if: ${{ github.event.pull_request.draft == false }}
     runs-on: ubuntu-latest
     outputs:
       is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}

.github/workflows/runtime_build_and_test.yml

@@ -280,6 +280,37 @@ jobs:
         if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn test ${{ matrix.params }} --ci --shard=${{ matrix.shard }}
 
+  # Hardcoded to improve parallelism
+  test-linter:
+    name: Test eslint-plugin-react-hooks
+    needs: [runtime_compiler_node_modules_cache]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: '.nvmrc'
+          cache: yarn
+          cache-dependency-path:  |
+            yarn.lock
+            compiler/yarn.lock
+      - name: Restore cached node_modules
+        uses: actions/cache@v4
+        id: node_modules
+        with:
+          path: |
+            **/node_modules
+          key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+      - name: Install runtime dependencies
+        run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - name: Install compiler dependencies
+        run: yarn install --frozen-lockfile
+        working-directory: compiler
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: ./scripts/react-compiler/build-compiler.sh && ./scripts/react-compiler/link-compiler.sh
+      - run: yarn workspace eslint-plugin-react-hooks test
+        
   # ----- BUILD -----
   build_and_lint:
     name: yarn build and lint

.github/workflows/runtime_discord_notify.yml

@@ -11,6 +11,7 @@ permissions: {}
 
 jobs:
   check_access:
+    if: ${{ github.event.pull_request.draft == false }}
     runs-on: ubuntu-latest
     outputs:
       is_member_or_collaborator: ${{ steps.check_is_member_or_collaborator.outputs.is_member_or_collaborator }}

.github/workflows/runtime_prereleases.yml

@@ -17,6 +17,17 @@ on:
         description: 'Whether to notify the team on Discord when the release fails. Useful if this workflow is called from an automation.'
         required: false
         type: boolean
+      only_packages:
+        description: Packages to publish (space separated)
+        type: string
+      skip_packages:
+        description: Packages to NOT publish (space separated)
+        type: string
+      dry:
+        required: true
+        description: Dry run instead of publish?
+        type: boolean
+        default: true
     secrets:
       DISCORD_WEBHOOK_URL:
         description: 'Discord webhook URL to notify on failure. Only required if enableFailureNotification is true.'
@@ -61,15 +72,41 @@ jobs:
         if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn --cwd scripts/release install --frozen-lockfile
         if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: cp ./scripts/release/ci-npmrc ~/.npmrc
       - run: |
           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 ${{ inputs.dist_tag }}
+      - name: Check prepared files
+        run: ls -R build/node_modules
+      - if: '${{ inputs.only_packages }}'
+        name: 'Publish ${{ inputs.only_packages }}'
+        run: |
+          scripts/release/publish.js \
+            --ci \
+            --skipTests \
+            --tags=${{ inputs.dist_tag }} \
+            --onlyPackages=${{ inputs.only_packages }} ${{ (inputs.dry && '') || '\'}}
+            ${{ inputs.dry && '--dry' || '' }}
+      - if: '${{ inputs.skip_packages }}'
+        name: 'Publish all packages EXCEPT ${{ inputs.skip_packages }}'
+        run: |
+          scripts/release/publish.js \
+            --ci \
+            --skipTests \
+            --tags=${{ inputs.dist_tag }} \
+            --skipPackages=${{ inputs.skip_packages }} ${{ (inputs.dry && '') || '\'}}
+            ${{ inputs.dry && '--dry' || '' }}
+      - if: '${{ !(inputs.skip_packages && inputs.only_packages) }}'
+        name: 'Publish all packages'
+        run: |
+          scripts/release/publish.js \
+            --ci \
+            --tags=${{ inputs.dist_tag }} ${{ (inputs.dry && '') || '\'}}
+            ${{ inputs.dry && '--dry' || '' }}
       - name: Notify Discord on failure
         if: failure() && inputs.enableFailureNotification == true
         uses: tsickert/discord-webhook@86dc739f3f165f16dadc5666051c367efa1692f4
         with:
           webhook-url: ${{ secrets.DISCORD_WEBHOOK_URL }}
           embed-author-name: "GitHub Actions"
-          embed-title: 'Publish of $${{ inputs.release_channel }} release failed'
+          embed-title: '[Runtime] Publish of ${{ inputs.release_channel }}@${{ inputs.dist_tag}} release failed'
           embed-url: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}/attempts/${{ github.run_attempt }}

.github/workflows/runtime_prereleases_manual.yml

@@ -5,6 +5,25 @@ on:
     inputs:
       prerelease_commit_sha:
         required: true
+      only_packages:
+        description: Packages to publish (space separated)
+        type: string
+      skip_packages:
+        description: Packages to NOT publish (space separated)
+        type: string
+      dry:
+        required: true
+        description: Dry run instead of publish?
+        type: boolean
+        default: true
+      experimental_only:
+        type: boolean
+        description: Only publish to the experimental tag
+        default: false
+      force_notify:
+        description: Force a Discord notification?
+        type: boolean
+        default: false
 
 permissions: {}
 
@@ -12,8 +31,26 @@ env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles
 
 jobs:
+  notify:
+    if: ${{ inputs.force_notify || inputs.dry == false || inputs.dry == 'false' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Discord Webhook Action
+        uses: tsickert/discord-webhook@86dc739f3f165f16dadc5666051c367efa1692f4
+        with:
+          webhook-url: ${{ secrets.DISCORD_WEBHOOK_URL }}
+          embed-author-name: ${{ github.event.sender.login }}
+          embed-author-url: ${{ github.event.sender.html_url }}
+          embed-author-icon-url: ${{ github.event.sender.avatar_url }}
+          embed-title: "⚠️ Publishing ${{ inputs.experimental_only && 'EXPERIMENTAL' || 'CANARY & EXPERIMENTAL' }} release ${{ (inputs.dry && ' (dry run)') || '' }}"
+          embed-description: |
+            ```json
+            ${{ toJson(inputs) }}
+            ```
+          embed-url: https://github.com/facebook/react/actions/runs/${{ github.run_id }}
 
   publish_prerelease_canary:
+    if: ${{ !inputs.experimental_only }}
     name: Publish to Canary channel
     uses: facebook/react/.github/workflows/runtime_prereleases.yml@main
     permissions:
@@ -33,6 +70,9 @@ jobs:
       # downstream consumers might still expect that tag. We can remove this
       # after some time has elapsed and the change has been communicated.
       dist_tag: canary,next
+      only_packages: ${{ inputs.only_packages }}
+      skip_packages: ${{ inputs.skip_packages }}
+      dry: ${{ inputs.dry }}
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -48,10 +88,15 @@ jobs:
     # different versions of the same package, even if they use different
     # dist tags.
     needs: publish_prerelease_canary
+    # Ensures the job runs even if canary is skipped
+    if: always()
     with:
       commit_sha: ${{ inputs.prerelease_commit_sha }}
       release_channel: experimental
       dist_tag: experimental
+      only_packages: ${{ inputs.only_packages }}
+      skip_packages: ${{ inputs.skip_packages }}
+      dry: ${{ inputs.dry }}
     secrets:
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
       GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/runtime_prereleases_nightly.yml

@@ -22,6 +22,7 @@ jobs:
       release_channel: stable
       dist_tag: canary,next
       enableFailureNotification: true
+      dry: false
     secrets:
       DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
@@ -43,6 +44,7 @@ jobs:
       release_channel: experimental
       dist_tag: experimental
       enableFailureNotification: true
+      dry: false
     secrets:
       DISCORD_WEBHOOK_URL: ${{ secrets.DISCORD_WEBHOOK_URL }}
       NPM_TOKEN: ${{ secrets.NPM_TOKEN }}

.github/workflows/runtime_releases_from_npm_manual.yml

@@ -110,7 +110,7 @@ jobs:
             --tags=${{ inputs.tags }} \
             --publishVersion=${{ inputs.version_to_publish }} \
             --onlyPackages=${{ inputs.only_packages }} ${{ (inputs.dry && '') || '\'}}
-            ${{ inputs.dry && '--dry'}}
+            ${{ inputs.dry && '--dry' || '' }}
       - if: '${{ inputs.skip_packages }}'
         name: 'Publish all packages EXCEPT ${{ inputs.skip_packages }}'
         run: |
@@ -119,7 +119,7 @@ jobs:
             --tags=${{ inputs.tags }} \
             --publishVersion=${{ inputs.version_to_publish }} \
             --skipPackages=${{ inputs.skip_packages }} ${{ (inputs.dry && '') || '\'}}
-            ${{ inputs.dry && '--dry'}}
+            ${{ inputs.dry && '--dry' || '' }}
       - name: Archive released package for debugging
         uses: actions/upload-artifact@v4
         with:

.github/workflows/shared_stale.yml

@@ -6,7 +6,10 @@ on:
     - cron: '0 * * * *'
   workflow_dispatch:
 
-permissions: {}
+permissions:
+  # https://github.com/actions/stale/tree/v9/?tab=readme-ov-file#recommended-permissions
+  issues: write
+  pull-requests: write
 
 env:
   TZ: /usr/share/zoneinfo/America/Los_Angeles

.prettierrc.js

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

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

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

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

@@ -41,6 +41,10 @@ const DynamicGatingOptionsSchema = z.object({
   source: z.string(),
 });
 export type DynamicGatingOptions = z.infer<typeof DynamicGatingOptionsSchema>;
+const CustomOptOutDirectiveSchema = z
+  .nullable(z.array(z.string()))
+  .default(null);
+type CustomOptOutDirective = z.infer<typeof CustomOptOutDirectiveSchema>;
 
 export type PluginOptions = {
   environment: EnvironmentConfig;
@@ -132,6 +136,11 @@ export type PluginOptions = {
    */
   ignoreUseNoForget: boolean;
 
+  /**
+   * Unstable / do not use
+   */
+  customOptOutDirectives: CustomOptOutDirective;
+
   sources: Array<string> | ((filename: string) => boolean) | null;
 
   /**
@@ -278,6 +287,7 @@ export const defaultOptions: PluginOptions = {
     return filename.indexOf('node_modules') === -1;
   },
   enableReanimatedCheck: true,
+  customOptOutDirectives: null,
   target: '19',
 } as const;
 
@@ -338,6 +348,21 @@ export function parsePluginOptions(obj: unknown): PluginOptions {
           }
           break;
         }
+        case 'customOptOutDirectives': {
+          const result = CustomOptOutDirectiveSchema.safeParse(value);
+          if (result.success) {
+            parsedOptions[key] = result.data;
+          } else {
+            CompilerError.throwInvalidConfig({
+              reason:
+                'Could not parse custom opt out directives. Update React Compiler config to fix the error',
+              description: `${fromZodError(result.error)}`,
+              loc: null,
+              suggestions: null,
+            });
+          }
+          break;
+        }
         default: {
           parsedOptions[key] = value;
         }

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

@@ -104,6 +104,8 @@ import {validateNoImpureFunctionsInRender} from '../Validation/ValidateNoImpureF
 import {CompilerError} from '..';
 import {validateStaticComponents} from '../Validation/ValidateStaticComponents';
 import {validateNoFreezingKnownMutableFunctions} from '../Validation/ValidateNoFreezingKnownMutableFunctions';
+import {inferMutationAliasingEffects} from '../Inference/InferMutationAliasingEffects';
+import {inferMutationAliasingRanges} from '../Inference/InferMutationAliasingRanges';
 
 export type CompilerPipelineValue =
   | {kind: 'ast'; name: string; value: CodegenFunction}
@@ -130,6 +132,7 @@ function run(
     mode,
     config,
     contextIdentifiers,
+    func,
     logger,
     filename,
     code,
@@ -226,15 +229,27 @@ function runWithEnvironment(
   analyseFunctions(hir);
   log({kind: 'hir', name: 'AnalyseFunctions', value: hir});
 
-  const fnEffectErrors = inferReferenceEffects(hir);
-  if (env.isInferredMemoEnabled) {
-    if (fnEffectErrors.length > 0) {
-      CompilerError.throw(fnEffectErrors[0]);
+  if (!env.config.enableNewMutationAliasingModel) {
+    const fnEffectErrors = inferReferenceEffects(hir);
+    if (env.isInferredMemoEnabled) {
+      if (fnEffectErrors.length > 0) {
+        CompilerError.throw(fnEffectErrors[0]);
+      }
+    }
+    log({kind: 'hir', name: 'InferReferenceEffects', value: hir});
+  } else {
+    const mutabilityAliasingErrors = inferMutationAliasingEffects(hir);
+    log({kind: 'hir', name: 'InferMutationAliasingEffects', value: hir});
+    if (env.isInferredMemoEnabled) {
+      if (mutabilityAliasingErrors.isErr()) {
+        throw mutabilityAliasingErrors.unwrapErr();
+      }
     }
   }
-  log({kind: 'hir', name: 'InferReferenceEffects', value: hir});
 
-  validateLocalsNotReassignedAfterRender(hir);
+  if (!env.config.enableNewMutationAliasingModel) {
+    validateLocalsNotReassignedAfterRender(hir);
+  }
 
   // Note: Has to come after infer reference effects because "dead" code may still affect inference
   deadCodeElimination(hir);
@@ -248,8 +263,21 @@ function runWithEnvironment(
   pruneMaybeThrows(hir);
   log({kind: 'hir', name: 'PruneMaybeThrows', value: hir});
 
-  inferMutableRanges(hir);
-  log({kind: 'hir', name: 'InferMutableRanges', value: hir});
+  if (!env.config.enableNewMutationAliasingModel) {
+    inferMutableRanges(hir);
+    log({kind: 'hir', name: 'InferMutableRanges', value: hir});
+  } else {
+    const mutabilityAliasingErrors = inferMutationAliasingRanges(hir, {
+      isFunctionExpression: false,
+    });
+    log({kind: 'hir', name: 'InferMutationAliasingRanges', value: hir});
+    if (env.isInferredMemoEnabled) {
+      if (mutabilityAliasingErrors.isErr()) {
+        throw mutabilityAliasingErrors.unwrapErr();
+      }
+      validateLocalsNotReassignedAfterRender(hir);
+    }
+  }
 
   if (env.isInferredMemoEnabled) {
     if (env.config.assertValidMutableRanges) {
@@ -257,7 +285,7 @@ function runWithEnvironment(
     }
 
     if (env.config.validateRefAccessDuringRender) {
-      validateNoRefAccessInRender(hir).unwrap();
+      // validateNoRefAccessInRender(hir).unwrap();
     }
 
     if (env.config.validateNoSetStateInRender) {
@@ -276,7 +304,10 @@ function runWithEnvironment(
       validateNoImpureFunctionsInRender(hir).unwrap();
     }
 
-    if (env.config.validateNoFreezingKnownMutableFunctions) {
+    if (
+      env.config.validateNoFreezingKnownMutableFunctions ||
+      env.config.enableNewMutationAliasingModel
+    ) {
       validateNoFreezingKnownMutableFunctions(hir).unwrap();
     }
   }

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

@@ -63,7 +63,16 @@ export function tryFindDirectiveEnablingMemoization(
 
 export function findDirectiveDisablingMemoization(
   directives: Array<t.Directive>,
+  {customOptOutDirectives}: PluginOptions,
 ): t.Directive | null {
+  if (customOptOutDirectives != null) {
+    return (
+      directives.find(
+        directive =>
+          customOptOutDirectives.indexOf(directive.value.value) !== -1,
+      ) ?? null
+    );
+  }
   return (
     directives.find(directive =>
       OPT_OUT_DIRECTIVES.has(directive.value.value),
@@ -394,7 +403,8 @@ export function compileProgram(
     code: pass.code,
     suppressions,
     hasModuleScopeOptOut:
-      findDirectiveDisablingMemoization(program.node.directives) != null,
+      findDirectiveDisablingMemoization(program.node.directives, pass.opts) !=
+      null,
   });
 
   const queue: Array<CompileSource> = findFunctionsToCompile(
@@ -571,7 +581,10 @@ function processFn(
     }
     directives = {
       optIn: optIn.unwrapOr(null),
-      optOut: findDirectiveDisablingMemoization(fn.node.body.directives),
+      optOut: findDirectiveDisablingMemoization(
+        fn.node.body.directives,
+        programContext.opts,
+      ),
     };
   }
 

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

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

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

@@ -47,7 +47,7 @@ import {
   makeType,
   promoteTemporary,
 } from './HIR';
-import HIRBuilder, {Bindings} from './HIRBuilder';
+import HIRBuilder, {Bindings, createTemporaryPlace} from './HIRBuilder';
 import {BuiltInArrayId} from './ObjectShape';
 
 /*
@@ -70,21 +70,23 @@ import {BuiltInArrayId} from './ObjectShape';
 export function lower(
   func: NodePath<t.Function>,
   env: Environment,
+  // Bindings captured from the outer function, in case lower() is called recursively (for lambdas)
   bindings: Bindings | null = null,
-  capturedRefs: Array<t.Identifier> = [],
-  // the outermost function being compiled, in case lower() is called recursively (for lambdas)
-  parent: NodePath<t.Function> | null = null,
+  capturedRefs: Map<t.Identifier, SourceLocation> = new Map(),
 ): Result<HIRFunction, CompilerError> {
-  const builder = new HIRBuilder(env, parent ?? func, bindings, capturedRefs);
+  const builder = new HIRBuilder(env, {
+    bindings,
+    context: capturedRefs,
+  });
   const context: HIRFunction['context'] = [];
 
-  for (const ref of capturedRefs ?? []) {
+  for (const [ref, loc] of capturedRefs ?? []) {
     context.push({
       kind: 'Identifier',
       identifier: builder.resolveBinding(ref),
       effect: Effect.Unknown,
       reactive: false,
-      loc: ref.loc ?? GeneratedSource,
+      loc,
     });
   }
 
@@ -179,6 +181,7 @@ export function lower(
       loc: GeneratedSource,
       value: lowerExpressionToTemporary(builder, body),
       id: makeInstructionId(0),
+      effects: null,
     };
     builder.terminateWithContinuation(terminal, fallthrough);
   } else if (body.isBlockStatement()) {
@@ -208,6 +211,7 @@ export function lower(
         loc: GeneratedSource,
       }),
       id: makeInstructionId(0),
+      effects: null,
     },
     null,
   );
@@ -215,9 +219,9 @@ export function lower(
   return Ok({
     id,
     params,
-    fnType: parent == null ? env.fnType : 'Other',
+    fnType: bindings == null ? env.fnType : 'Other',
     returnTypeAnnotation: null, // TODO: extract the actual return type node if present
-    returnType: makeType(),
+    returns: createTemporaryPlace(env, func.node.loc ?? GeneratedSource),
     body: builder.build(),
     context,
     generator: func.node.generator === true,
@@ -225,6 +229,7 @@ export function lower(
     loc: func.node.loc ?? GeneratedSource,
     env,
     effects: null,
+    aliasingEffects: null,
     directives,
   });
 }
@@ -285,6 +290,7 @@ function lowerStatement(
         loc: stmt.node.loc ?? GeneratedSource,
         value,
         id: makeInstructionId(0),
+        effects: null,
       };
       builder.terminate(terminal, 'block');
       return;
@@ -1235,6 +1241,7 @@ function lowerStatement(
           kind: 'Debugger',
           loc,
         },
+        effects: null,
         loc,
       });
       return;
@@ -1892,6 +1899,7 @@ function lowerExpression(
           place: leftValue,
           loc: exprLoc,
         },
+        effects: null,
         loc: exprLoc,
       });
       builder.terminateWithContinuation(
@@ -2827,6 +2835,7 @@ function lowerOptionalCallExpression(
           args,
           loc,
         },
+        effects: null,
         loc,
       });
     } else {
@@ -2840,6 +2849,7 @@ function lowerOptionalCallExpression(
           args,
           loc,
         },
+        effects: null,
         loc,
       });
     }
@@ -3417,7 +3427,7 @@ function lowerFunction(
     | t.ObjectMethod
   >,
 ): LoweredFunction | null {
-  const componentScope: Scope = builder.parentFunction.scope;
+  const componentScope: Scope = builder.environment.parentFunction.scope;
   const capturedContext = gatherCapturedContext(expr, componentScope);
 
   /*
@@ -3432,8 +3442,7 @@ function lowerFunction(
     expr,
     builder.environment,
     builder.bindings,
-    [...builder.context, ...capturedContext],
-    builder.parentFunction,
+    new Map([...builder.context, ...capturedContext]),
   );
   let loweredFunc: HIRFunction;
   if (lowering.isErr()) {
@@ -3456,7 +3465,7 @@ function lowerExpressionToTemporary(
   return lowerValueToTemporary(builder, value);
 }
 
-function lowerValueToTemporary(
+export function lowerValueToTemporary(
   builder: HIRBuilder,
   value: InstructionValue,
 ): Place {
@@ -3466,9 +3475,10 @@ function lowerValueToTemporary(
   const place: Place = buildTemporaryPlace(builder, value.loc);
   builder.push({
     id: makeInstructionId(0),
-    value: value,
-    loc: value.loc,
     lvalue: {...place},
+    value: value,
+    effects: null,
+    loc: value.loc,
   });
   return place;
 }
@@ -4151,6 +4161,11 @@ function captureScopes({from, to}: {from: Scope; to: Scope}): Set<Scope> {
   return scopes;
 }
 
+/**
+ * Returns a mapping of "context" identifiers — references to free variables that
+ * will become part of the function expression's `context` array — along with the
+ * source location of their first reference within the function.
+ */
 function gatherCapturedContext(
   fn: NodePath<
     | t.FunctionExpression
@@ -4159,8 +4174,8 @@ function gatherCapturedContext(
     | t.ObjectMethod
   >,
   componentScope: Scope,
-): Array<t.Identifier> {
-  const capturedIds = new Set<t.Identifier>();
+): Map<t.Identifier, SourceLocation> {
+  const capturedIds = new Map<t.Identifier, SourceLocation>();
 
   /*
    * Capture all the scopes from the parent of this function up to and including
@@ -4203,8 +4218,15 @@ function gatherCapturedContext(
 
     // Add the base identifier binding as a dependency.
     const binding = baseIdentifier.scope.getBinding(baseIdentifier.node.name);
-    if (binding !== undefined && pureScopes.has(binding.scope)) {
-      capturedIds.add(binding.identifier);
+    if (
+      binding !== undefined &&
+      pureScopes.has(binding.scope) &&
+      !capturedIds.has(binding.identifier)
+    ) {
+      capturedIds.set(
+        binding.identifier,
+        path.node.loc ?? binding.identifier.loc ?? GeneratedSource,
+      );
     }
   }
 
@@ -4241,7 +4263,7 @@ function gatherCapturedContext(
     },
   });
 
-  return [...capturedIds.keys()];
+  return capturedIds;
 }
 
 function notNull<T>(value: T | null): value is T {

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

@@ -241,7 +241,10 @@ type PropertyPathNode =
 class PropertyPathRegistry {
   roots: Map<IdentifierId, RootNode> = new Map();
 
-  getOrCreateIdentifier(identifier: Identifier): PropertyPathNode {
+  getOrCreateIdentifier(
+    identifier: Identifier,
+    reactive: boolean,
+  ): PropertyPathNode {
     /**
      * Reads from a statically scoped variable are always safe in JS,
      * with the exception of TDZ (not addressed by this pass).
@@ -255,12 +258,19 @@ class PropertyPathRegistry {
         optionalProperties: new Map(),
         fullPath: {
           identifier,
+          reactive,
           path: [],
         },
         hasOptional: false,
         parent: null,
       };
       this.roots.set(identifier.id, rootNode);
+    } else {
+      CompilerError.invariant(reactive === rootNode.fullPath.reactive, {
+        reason:
+          '[HoistablePropertyLoads] Found inconsistencies in `reactive` flag when deduping identifier reads within the same scope',
+        loc: identifier.loc,
+      });
     }
     return rootNode;
   }
@@ -278,6 +288,7 @@ class PropertyPathRegistry {
         parent: parent,
         fullPath: {
           identifier: parent.fullPath.identifier,
+          reactive: parent.fullPath.reactive,
           path: parent.fullPath.path.concat(entry),
         },
         hasOptional: parent.hasOptional || entry.optional,
@@ -293,7 +304,7 @@ class PropertyPathRegistry {
      * so all subpaths of a PropertyLoad should already exist
      * (e.g. a.b is added before a.b.c),
      */
-    let currNode = this.getOrCreateIdentifier(n.identifier);
+    let currNode = this.getOrCreateIdentifier(n.identifier, n.reactive);
     if (n.path.length === 0) {
       return currNode;
     }
@@ -315,10 +326,11 @@ function getMaybeNonNullInInstruction(
   instr: InstructionValue,
   context: CollectHoistablePropertyLoadsContext,
 ): PropertyPathNode | null {
-  let path = null;
+  let path: ReactiveScopeDependency | null = null;
   if (instr.kind === 'PropertyLoad') {
     path = context.temporaries.get(instr.object.identifier.id) ?? {
       identifier: instr.object.identifier,
+      reactive: instr.object.reactive,
       path: [],
     };
   } else if (instr.kind === 'Destructure') {
@@ -381,7 +393,7 @@ function collectNonNullsInBlocks(
   ) {
     const identifier = fn.params[0].identifier;
     knownNonNullIdentifiers.add(
-      context.registry.getOrCreateIdentifier(identifier),
+      context.registry.getOrCreateIdentifier(identifier, true),
     );
   }
   const nodes = new Map<
@@ -616,9 +628,11 @@ function reduceMaybeOptionalChains(
     changed = false;
 
     for (const original of optionalChainNodes) {
-      let {identifier, path: origPath} = original.fullPath;
-      let currNode: PropertyPathNode =
-        registry.getOrCreateIdentifier(identifier);
+      let {identifier, path: origPath, reactive} = original.fullPath;
+      let currNode: PropertyPathNode = registry.getOrCreateIdentifier(
+        identifier,
+        reactive,
+      );
       for (let i = 0; i < origPath.length; i++) {
         const entry = origPath[i];
         // If the base is known to be non-null, replace with a non-optional load

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

@@ -290,6 +290,7 @@ function traverseOptionalBlock(
     );
     baseObject = {
       identifier: maybeTest.instructions[0].value.place.identifier,
+      reactive: maybeTest.instructions[0].value.place.reactive,
       path,
     };
     test = maybeTest.terminal;
@@ -391,6 +392,7 @@ function traverseOptionalBlock(
   );
   const load = {
     identifier: baseObject.identifier,
+    reactive: baseObject.reactive,
     path: [
       ...baseObject.path,
       {

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

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

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

@@ -47,7 +47,7 @@ import {
   ShapeRegistry,
   addHook,
 } from './ObjectShape';
-import {Scope as BabelScope} from '@babel/traverse';
+import {Scope as BabelScope, NodePath} from '@babel/traverse';
 import {TypeSchema} from './TypeSchema';
 
 export const ReactElementSymbolSchema = z.object({
@@ -243,6 +243,11 @@ export const EnvironmentConfigSchema = z.object({
    */
   enableUseTypeAnnotations: z.boolean().default(false),
 
+  /**
+   * Enable a new model for mutability and aliasing inference
+   */
+  enableNewMutationAliasingModel: z.boolean().default(true),
+
   /**
    * Enables inference of optional dependency chains. Without this flag
    * a property chain such as `props?.items?.foo` will infer as a dep on
@@ -675,6 +680,7 @@ export class Environment {
 
   #contextIdentifiers: Set<t.Identifier>;
   #hoistedIdentifiers: Set<t.Identifier>;
+  parentFunction: NodePath<t.Function>;
 
   constructor(
     scope: BabelScope,
@@ -682,6 +688,7 @@ export class Environment {
     compilerMode: CompilerMode,
     config: EnvironmentConfig,
     contextIdentifiers: Set<t.Identifier>,
+    parentFunction: NodePath<t.Function>, // the outermost function being compiled
     logger: Logger | null,
     filename: string | null,
     code: string | null,
@@ -740,6 +747,7 @@ export class Environment {
       this.#moduleTypes.set(REANIMATED_MODULE_NAME, reanimatedModuleType);
     }
 
+    this.parentFunction = parentFunction;
     this.#contextIdentifiers = contextIdentifiers;
     this.#hoistedIdentifiers = new Set();
   }

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

@@ -17,6 +17,7 @@ import {
   BuiltInSetId,
   BuiltInUseActionStateId,
   BuiltInUseContextHookId,
+  BuiltInUseEffectEventId,
   BuiltInUseEffectHookId,
   BuiltInUseInsertionEffectHookId,
   BuiltInUseLayoutEffectHookId,
@@ -27,6 +28,7 @@ import {
   BuiltInUseTransitionId,
   BuiltInWeakMapId,
   BuiltInWeakSetId,
+  BuiltinEffectEventId,
   ReanimatedSharedValueId,
   ShapeRegistry,
   addFunction,
@@ -642,6 +644,41 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         calleeEffect: Effect.Read,
         hookKind: 'useEffect',
         returnValueKind: ValueKind.Frozen,
+        aliasing: {
+          receiver: '@receiver',
+          params: [],
+          rest: '@rest',
+          returns: '@returns',
+          temporaries: ['@effect'],
+          effects: [
+            // Freezes the function and deps
+            {
+              kind: 'Freeze',
+              value: '@rest',
+              reason: ValueReason.Effect,
+            },
+            // Internally creates an effect object that captures the function and deps
+            {
+              kind: 'Create',
+              into: '@effect',
+              value: ValueKind.Frozen,
+              reason: ValueReason.KnownReturnSignature,
+            },
+            // The effect stores the function and dependencies
+            {
+              kind: 'Capture',
+              from: '@rest',
+              into: '@effect',
+            },
+            // Returns undefined
+            {
+              kind: 'Create',
+              into: '@returns',
+              value: ValueKind.Primitive,
+              reason: ValueReason.KnownReturnSignature,
+            },
+          ],
+        },
       },
       BuiltInUseEffectHookId,
     ),
@@ -722,6 +759,27 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       BuiltInFireId,
     ),
   ],
+  [
+    'useEffectEvent',
+    addHook(
+      DEFAULT_SHAPES,
+      {
+        positionalParams: [],
+        restParam: Effect.Freeze,
+        returnType: {
+          kind: 'Function',
+          return: {kind: 'Poly'},
+          shapeId: BuiltinEffectEventId,
+          isConstructor: false,
+        },
+        calleeEffect: Effect.Read,
+        hookKind: 'useEffectEvent',
+        // Frozen because it should not mutate any locally-bound values
+        returnValueKind: ValueKind.Frozen,
+      },
+      BuiltInUseEffectEventId,
+    ),
+  ],
 ];
 
 TYPED_GLOBALS.push(
@@ -847,6 +905,7 @@ export function installTypeConfig(
         noAlias: typeConfig.noAlias === true,
         mutableOnlyIfOperandsAreMutable:
           typeConfig.mutableOnlyIfOperandsAreMutable === true,
+        aliasing: typeConfig.aliasing,
       });
     }
     case 'hook': {
@@ -864,6 +923,7 @@ export function installTypeConfig(
         ),
         returnValueKind: typeConfig.returnValueKind ?? ValueKind.Frozen,
         noAlias: typeConfig.noAlias === true,
+        aliasing: typeConfig.aliasing,
       });
     }
     case 'object': {

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

@@ -13,6 +13,7 @@ import {Environment, ReactFunctionType} from './Environment';
 import type {HookKind} from './ObjectShape';
 import {Type, makeType} from './Types';
 import {z} from 'zod';
+import type {AliasingEffect} from '../Inference/AliasingEffects';
 
 /*
  * *******************************************************************************************
@@ -100,6 +101,7 @@ export type ReactiveInstruction = {
   id: InstructionId;
   lvalue: Place | null;
   value: ReactiveValue;
+  effects?: Array<AliasingEffect> | null; // TODO make non-optional
   loc: SourceLocation;
 };
 
@@ -277,13 +279,14 @@ export type HIRFunction = {
   env: Environment;
   params: Array<Place | SpreadPattern>;
   returnTypeAnnotation: t.FlowType | t.TSType | null;
-  returnType: Type;
+  returns: Place;
   context: Array<Place>;
   effects: Array<FunctionEffect> | null;
   body: HIR;
   generator: boolean;
   async: boolean;
   directives: Array<string>;
+  aliasingEffects?: Array<AliasingEffect> | null;
 };
 
 export type FunctionEffect =
@@ -449,6 +452,7 @@ export type ReturnTerminal = {
   value: Place;
   id: InstructionId;
   fallthrough?: never;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type GotoTerminal = {
@@ -609,6 +613,7 @@ export type MaybeThrowTerminal = {
   id: InstructionId;
   loc: SourceLocation;
   fallthrough?: never;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type ReactiveScopeTerminal = {
@@ -645,12 +650,14 @@ export type Instruction = {
   lvalue: Place;
   value: InstructionValue;
   loc: SourceLocation;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type TInstruction<T extends InstructionValue> = {
   id: InstructionId;
   lvalue: Place;
   value: T;
+  effects: Array<AliasingEffect> | null;
   loc: SourceLocation;
 };
 
@@ -1380,6 +1387,21 @@ export enum ValueReason {
    */
   JsxCaptured = 'jsx-captured',
 
+  /**
+   * Argument to a hook
+   */
+  HookCaptured = 'hook-captured',
+
+  /**
+   * Return value of a hook
+   */
+  HookReturn = 'hook-return',
+
+  /**
+   * Passed to an effect
+   */
+  Effect = 'effect',
+
   /**
    * Return value of a function with known frozen return value, e.g. `useState`.
    */
@@ -1430,6 +1452,20 @@ export const ValueKindSchema = z.enum([
   ValueKind.Context,
 ]);
 
+export const ValueReasonSchema = z.enum([
+  ValueReason.Context,
+  ValueReason.Effect,
+  ValueReason.Global,
+  ValueReason.HookCaptured,
+  ValueReason.HookReturn,
+  ValueReason.JsxCaptured,
+  ValueReason.KnownReturnSignature,
+  ValueReason.Other,
+  ValueReason.ReactiveFunctionArgument,
+  ValueReason.ReducerState,
+  ValueReason.State,
+]);
+
 // The effect with which a value is modified.
 export enum Effect {
   // Default value: not allowed after lifetime inference
@@ -1568,6 +1604,18 @@ export type DependencyPathEntry = {
 export type DependencyPath = Array<DependencyPathEntry>;
 export type ReactiveScopeDependency = {
   identifier: Identifier;
+  /**
+   * Reflects whether the base identifier is reactive. Note that some reactive
+   * objects may have non-reactive properties, but we do not currently track
+   * this.
+   *
+   * ```js
+   * // Technically, result[0] is reactive and result[1] is not.
+   * // Currently, both dependencies would be marked as reactive.
+   * const result = useState();
+   * ```
+   */
+  reactive: boolean;
   path: DependencyPath;
 };
 
@@ -1721,6 +1769,10 @@ export function isUseStateType(id: Identifier): boolean {
   return id.type.kind === 'Object' && id.type.shapeId === 'BuiltInUseState';
 }
 
+export function isJsxType(type: Type): boolean {
+  return type.kind === 'Object' && type.shapeId === 'BuiltInJsx';
+}
+
 export function isRefOrRefValue(id: Identifier): boolean {
   return isUseRefType(id) || isRefValueType(id);
 }
@@ -1773,6 +1825,13 @@ export function isFireFunctionType(id: Identifier): boolean {
   );
 }
 
+export function isEffectEventFunctionType(id: Identifier): boolean {
+  return (
+    id.type.kind === 'Function' &&
+    id.type.shapeId === 'BuiltInEffectEventFunction'
+  );
+}
+
 export function isStableType(id: Identifier): boolean {
   return (
     isSetStateType(id) ||

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

@@ -106,11 +106,10 @@ export default class HIRBuilder {
   #current: WipBlock;
   #entry: BlockId;
   #scopes: Array<Scope> = [];
-  #context: Array<t.Identifier>;
+  #context: Map<t.Identifier, SourceLocation>;
   #bindings: Bindings;
   #env: Environment;
   #exceptionHandlerStack: Array<BlockId> = [];
-  parentFunction: NodePath<t.Function>;
   errors: CompilerError = new CompilerError();
   /**
    * Traversal context: counts the number of `fbt` tag parents
@@ -122,7 +121,7 @@ export default class HIRBuilder {
     return this.#env.nextIdentifierId;
   }
 
-  get context(): Array<t.Identifier> {
+  get context(): Map<t.Identifier, SourceLocation> {
     return this.#context;
   }
 
@@ -136,16 +135,17 @@ export default class HIRBuilder {
 
   constructor(
     env: Environment,
-    parentFunction: NodePath<t.Function>, // the outermost function being compiled
-    bindings: Bindings | null = null,
-    context: Array<t.Identifier> | null = null,
+    options?: {
+      bindings?: Bindings | null;
+      context?: Map<t.Identifier, SourceLocation>;
+      entryBlockKind?: BlockKind;
+    },
   ) {
     this.#env = env;
-    this.#bindings = bindings ?? new Map();
-    this.parentFunction = parentFunction;
-    this.#context = context ?? [];
+    this.#bindings = options?.bindings ?? new Map();
+    this.#context = options?.context ?? new Map();
     this.#entry = makeBlockId(env.nextBlockId);
-    this.#current = newBlock(this.#entry, 'block');
+    this.#current = newBlock(this.#entry, options?.entryBlockKind ?? 'block');
   }
 
   currentBlockKind(): BlockKind {
@@ -165,6 +165,7 @@ export default class HIRBuilder {
           handler: exceptionHandler,
           id: makeInstructionId(0),
           loc: instruction.loc,
+          effects: null,
         },
         continuationBlock,
       );
@@ -239,7 +240,7 @@ export default class HIRBuilder {
 
     // Check if the binding is from module scope
     const outerBinding =
-      this.parentFunction.scope.parent.getBinding(originalName);
+      this.#env.parentFunction.scope.parent.getBinding(originalName);
     if (babelBinding === outerBinding) {
       const path = babelBinding.path;
       if (path.isImportDefaultSpecifier()) {
@@ -293,7 +294,7 @@ export default class HIRBuilder {
     const binding = this.#resolveBabelBinding(path);
     if (binding) {
       // Check if the binding is from module scope, if so return null
-      const outerBinding = this.parentFunction.scope.parent.getBinding(
+      const outerBinding = this.#env.parentFunction.scope.parent.getBinding(
         path.node.name,
       );
       if (binding === outerBinding) {
@@ -376,7 +377,7 @@ export default class HIRBuilder {
   }
 
   // Terminate the current block w the given terminal, and start a new block
-  terminate(terminal: Terminal, nextBlockKind: BlockKind | null): void {
+  terminate(terminal: Terminal, nextBlockKind: BlockKind | null): BlockId {
     const {id: blockId, kind, instructions} = this.#current;
     this.#completed.set(blockId, {
       kind,
@@ -390,6 +391,7 @@ export default class HIRBuilder {
       const nextId = this.#env.nextBlockId;
       this.#current = newBlock(nextId, nextBlockKind);
     }
+    return blockId;
   }
 
   /*
@@ -746,6 +748,11 @@ function getReversePostorderedBlocks(func: HIR): HIR['blocks'] {
      * (eg bb2 then bb1), we ensure that they get reversed back to the correct order.
      */
     const block = func.blocks.get(blockId)!;
+    CompilerError.invariant(block != null, {
+      reason: '[HIRBuilder] Unexpected null block',
+      description: `expected block ${blockId} to exist`,
+      loc: GeneratedSource,
+    });
     const successors = [...eachTerminalSuccessor(block.terminal)].reverse();
     const fallthrough = terminalFallthrough(block.terminal);
 

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

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

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

@@ -6,14 +6,30 @@
  */
 
 import {CompilerError} from '../CompilerError';
-import {Effect, ValueKind, ValueReason} from './HIR';
+import {AliasingEffect, AliasingSignature} from '../Inference/AliasingEffects';
+import {assertExhaustive} from '../Utils/utils';
+import {
+  Effect,
+  GeneratedSource,
+  Hole,
+  makeDeclarationId,
+  makeIdentifierId,
+  makeInstructionId,
+  Place,
+  SourceLocation,
+  SpreadPattern,
+  ValueKind,
+  ValueReason,
+} from './HIR';
 import {
   BuiltInType,
   FunctionType,
+  makeType,
   ObjectType,
   PolyType,
   PrimitiveType,
 } from './Types';
+import {AliasingEffectConfig, AliasingSignatureConfig} from './TypeSchema';
 
 /*
  * This file exports types and defaults for JavaScript object shapes. These are
@@ -42,13 +58,20 @@ function createAnonId(): string {
 export function addFunction(
   registry: ShapeRegistry,
   properties: Iterable<[string, BuiltInType | PolyType]>,
-  fn: Omit<FunctionSignature, 'hookKind'>,
+  fn: Omit<FunctionSignature, 'hookKind' | 'aliasing'> & {
+    aliasing?: AliasingSignatureConfig | null | undefined;
+  },
   id: string | null = null,
   isConstructor: boolean = false,
 ): FunctionType {
   const shapeId = id ?? createAnonId();
+  const aliasing =
+    fn.aliasing != null
+      ? parseAliasingSignatureConfig(fn.aliasing, '<builtin>', GeneratedSource)
+      : null;
   addShape(registry, shapeId, properties, {
     ...fn,
+    aliasing,
     hookKind: null,
   });
   return {
@@ -66,11 +89,18 @@ export function addFunction(
  */
 export function addHook(
   registry: ShapeRegistry,
-  fn: FunctionSignature & {hookKind: HookKind},
+  fn: Omit<FunctionSignature, 'aliasing'> & {
+    hookKind: HookKind;
+    aliasing?: AliasingSignatureConfig | null | undefined;
+  },
   id: string | null = null,
 ): FunctionType {
   const shapeId = id ?? createAnonId();
-  addShape(registry, shapeId, [], fn);
+  const aliasing =
+    fn.aliasing != null
+      ? parseAliasingSignatureConfig(fn.aliasing, '<builtin>', GeneratedSource)
+      : null;
+  addShape(registry, shapeId, [], {...fn, aliasing});
   return {
     kind: 'Function',
     return: fn.returnType,
@@ -79,6 +109,129 @@ export function addHook(
   };
 }
 
+function parseAliasingSignatureConfig(
+  typeConfig: AliasingSignatureConfig,
+  moduleName: string,
+  loc: SourceLocation,
+): AliasingSignature {
+  const lifetimes = new Map<string, Place>();
+  function define(temp: string): Place {
+    CompilerError.invariant(!lifetimes.has(temp), {
+      reason: `Invalid type configuration for module`,
+      description: `Expected aliasing signature to have unique names for receiver, params, rest, returns, and temporaries in module '${moduleName}'`,
+      loc,
+    });
+    const place = signatureArgument(lifetimes.size);
+    lifetimes.set(temp, place);
+    return place;
+  }
+  function lookup(temp: string): Place {
+    const place = lifetimes.get(temp);
+    CompilerError.invariant(place != null, {
+      reason: `Invalid type configuration for module`,
+      description: `Expected aliasing signature effects to reference known names from receiver/params/rest/returns/temporaries, but '${temp}' is not a known name in '${moduleName}'`,
+      loc,
+    });
+    return place;
+  }
+  const receiver = define(typeConfig.receiver);
+  const params = typeConfig.params.map(define);
+  const rest = typeConfig.rest != null ? define(typeConfig.rest) : null;
+  const returns = define(typeConfig.returns);
+  const temporaries = typeConfig.temporaries.map(define);
+  const effects = typeConfig.effects.map(
+    (effect: AliasingEffectConfig): AliasingEffect => {
+      switch (effect.kind) {
+        case 'CreateFrom':
+        case 'Capture':
+        case 'Alias':
+        case 'Assign': {
+          const from = lookup(effect.from);
+          const into = lookup(effect.into);
+          return {
+            kind: effect.kind,
+            from,
+            into,
+          };
+        }
+        case 'Mutate':
+        case 'MutateTransitiveConditionally': {
+          const value = lookup(effect.value);
+          return {kind: effect.kind, value};
+        }
+        case 'Create': {
+          const into = lookup(effect.into);
+          return {
+            kind: 'Create',
+            into,
+            reason: effect.reason,
+            value: effect.value,
+          };
+        }
+        case 'Freeze': {
+          const value = lookup(effect.value);
+          return {
+            kind: 'Freeze',
+            value,
+            reason: effect.reason,
+          };
+        }
+        case 'Impure': {
+          const place = lookup(effect.place);
+          return {
+            kind: 'Impure',
+            place,
+            error: CompilerError.throwTodo({
+              reason: 'Support impure effect declarations',
+              loc: GeneratedSource,
+            }),
+          };
+        }
+        case 'Apply': {
+          const receiver = lookup(effect.receiver);
+          const fn = lookup(effect.function);
+          const args: Array<Place | SpreadPattern | Hole> = effect.args.map(
+            arg => {
+              if (typeof arg === 'string') {
+                return lookup(arg);
+              } else if (arg.kind === 'Spread') {
+                return {kind: 'Spread', place: lookup(arg.place)};
+              } else {
+                return arg;
+              }
+            },
+          );
+          const into = lookup(effect.into);
+          return {
+            kind: 'Apply',
+            receiver,
+            function: fn,
+            mutatesFunction: effect.mutatesFunction,
+            args,
+            into,
+            loc,
+            signature: null,
+          };
+        }
+        default: {
+          assertExhaustive(
+            effect,
+            `Unexpected effect kind '${(effect as any).kind}'`,
+          );
+        }
+      }
+    },
+  );
+  return {
+    receiver: receiver.identifier.id,
+    params: params.map(p => p.identifier.id),
+    rest: rest != null ? rest.identifier.id : null,
+    returns: returns.identifier.id,
+    temporaries,
+    effects,
+  };
+}
+
 /*
  * Add an object to an existing ShapeRegistry.
  *
@@ -131,6 +284,7 @@ export type HookKind =
   | 'useCallback'
   | 'useTransition'
   | 'useImperativeHandle'
+  | 'useEffectEvent'
   | 'Custom';
 
 /*
@@ -179,6 +333,8 @@ export type FunctionSignature = {
   impure?: boolean;
 
   canonicalName?: string;
+
+  aliasing?: AliasingSignature | null | undefined;
 };
 
 /*
@@ -226,6 +382,8 @@ export const BuiltInUseTransitionId = 'BuiltInUseTransition';
 export const BuiltInStartTransitionId = 'BuiltInStartTransition';
 export const BuiltInFireId = 'BuiltInFire';
 export const BuiltInFireFunctionId = 'BuiltInFireFunction';
+export const BuiltInUseEffectEventId = 'BuiltInUseEffectEvent';
+export const BuiltinEffectEventId = 'BuiltInEffectEventFunction';
 
 // See getReanimatedModuleType() in Globals.ts — this is part of supporting Reanimated's ref-like types
 export const ReanimatedSharedValueId = 'ReanimatedSharedValueId';
@@ -302,6 +460,30 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       returnType: PRIMITIVE_TYPE,
       calleeEffect: Effect.Store,
       returnValueKind: ValueKind.Primitive,
+      aliasing: {
+        receiver: '@receiver',
+        params: [],
+        rest: '@rest',
+        returns: '@returns',
+        temporaries: [],
+        effects: [
+          // Push directly mutates the array itself
+          {kind: 'Mutate', value: '@receiver'},
+          // The arguments are captured into the array
+          {
+            kind: 'Capture',
+            from: '@rest',
+            into: '@receiver',
+          },
+          // Returns the new length, a primitive
+          {
+            kind: 'Create',
+            into: '@returns',
+            value: ValueKind.Primitive,
+            reason: ValueReason.KnownReturnSignature,
+          },
+        ],
+      },
     }),
   ],
   [
@@ -332,6 +514,60 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       returnValueKind: ValueKind.Mutable,
       noAlias: true,
       mutableOnlyIfOperandsAreMutable: true,
+      aliasing: {
+        receiver: '@receiver',
+        params: ['@callback'],
+        rest: null,
+        returns: '@returns',
+        temporaries: [
+          // Temporary representing captured items of the receiver
+          '@item',
+          // Temporary representing the result of the callback
+          '@callbackReturn',
+          /*
+           * Undefined `this` arg to the callback. Note the signature does not
+           * support passing an explicit thisArg second param
+           */
+          '@thisArg',
+        ],
+        effects: [
+          // Map creates a new mutable array
+          {
+            kind: 'Create',
+            into: '@returns',
+            value: ValueKind.Mutable,
+            reason: ValueReason.KnownReturnSignature,
+          },
+          // The first arg to the callback is an item extracted from the receiver array
+          {
+            kind: 'CreateFrom',
+            from: '@receiver',
+            into: '@item',
+          },
+          // The undefined this for the callback
+          {
+            kind: 'Create',
+            into: '@thisArg',
+            value: ValueKind.Primitive,
+            reason: ValueReason.KnownReturnSignature,
+          },
+          // calls the callback, returning the result into a temporary
+          {
+            kind: 'Apply',
+            receiver: '@thisArg',
+            args: ['@item', {kind: 'Hole'}, '@receiver'],
+            function: '@callback',
+            into: '@callbackReturn',
+            mutatesFunction: false,
+          },
+          // captures the result of the callback into the return array
+          {
+            kind: 'Capture',
+            from: '@callbackReturn',
+            into: '@returns',
+          },
+        ],
+      },
     }),
   ],
   [
@@ -479,6 +715,32 @@ addObject(BUILTIN_SHAPES, BuiltInSetId, [
       calleeEffect: Effect.Store,
       // returnValueKind is technically dependent on the ValueKind of the set itself
       returnValueKind: ValueKind.Mutable,
+      aliasing: {
+        receiver: '@receiver',
+        params: [],
+        rest: '@rest',
+        returns: '@returns',
+        temporaries: [],
+        effects: [
+          // Set.add returns the receiver Set
+          {
+            kind: 'Assign',
+            from: '@receiver',
+            into: '@returns',
+          },
+          // Set.add mutates the set itself
+          {
+            kind: 'Mutate',
+            value: '@receiver',
+          },
+          // Captures the rest params into the set
+          {
+            kind: 'Capture',
+            from: '@rest',
+            into: '@receiver',
+          },
+        ],
+      },
     }),
   ],
   [
@@ -948,6 +1210,19 @@ addObject(BUILTIN_SHAPES, BuiltInRefValueId, [
   ['*', {kind: 'Object', shapeId: BuiltInRefValueId}],
 ]);
 
+addFunction(
+  BUILTIN_SHAPES,
+  [],
+  {
+    positionalParams: [],
+    restParam: Effect.ConditionallyMutate,
+    returnType: {kind: 'Poly'},
+    calleeEffect: Effect.ConditionallyMutate,
+    returnValueKind: ValueKind.Mutable,
+  },
+  BuiltinEffectEventId,
+);
+
 /**
  * MixedReadOnly =
  *   | primitive
@@ -1166,6 +1441,53 @@ export const DefaultNonmutatingHook = addHook(
     calleeEffect: Effect.Read,
     hookKind: 'Custom',
     returnValueKind: ValueKind.Frozen,
+    aliasing: {
+      receiver: '@receiver',
+      params: [],
+      rest: '@rest',
+      returns: '@returns',
+      temporaries: [],
+      effects: [
+        // Freeze the arguments
+        {
+          kind: 'Freeze',
+          value: '@rest',
+          reason: ValueReason.HookCaptured,
+        },
+        // Returns a frozen value
+        {
+          kind: 'Create',
+          into: '@returns',
+          value: ValueKind.Frozen,
+          reason: ValueReason.HookReturn,
+        },
+        // May alias any arguments into the return
+        {
+          kind: 'Alias',
+          from: '@rest',
+          into: '@returns',
+        },
+      ],
+    },
   },
   'DefaultNonmutatingHook',
 );
+
+export function signatureArgument(id: number): Place {
+  const place: Place = {
+    kind: 'Identifier',
+    effect: Effect.Unknown,
+    loc: GeneratedSource,
+    reactive: false,
+    identifier: {
+      declarationId: makeDeclarationId(id),
+      id: makeIdentifierId(id),
+      loc: GeneratedSource,
+      mutableRange: {start: makeInstructionId(0), end: makeInstructionId(0)},
+      name: null,
+      scope: null,
+      type: makeType(),
+    },
+  };
+  return place;
+}

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

@@ -35,6 +35,7 @@ import type {
   Type,
 } from './HIR';
 import {GotoVariant, InstructionKind} from './HIR';
+import {AliasingEffect, AliasingSignature} from '../Inference/AliasingEffects';
 
 export type Options = {
   indent: number;
@@ -53,6 +54,8 @@ export function printFunction(fn: HIRFunction): string {
   let definition = '';
   if (fn.id !== null) {
     definition += fn.id;
+  } else {
+    definition += '<<anonymous>>';
   }
   if (fn.params.length !== 0) {
     definition +=
@@ -67,13 +70,13 @@ export function printFunction(fn: HIRFunction): string {
         })
         .join(', ') +
       ')';
+  } else {
+    definition += '()';
   }
-  if (definition.length !== 0) {
-    output.push(definition);
-  }
-  output.push(printType(fn.returnType));
-  output.push(printHIR(fn.body));
+  definition += `: ${printPlace(fn.returns)}`;
+  output.push(definition);
   output.push(...fn.directives);
+  output.push(printHIR(fn.body));
   return output.join('\n');
 }
 
@@ -151,7 +154,10 @@ export function printMixedHIR(
 
 export function printInstruction(instr: ReactiveInstruction): string {
   const id = `[${instr.id}]`;
-  const value = printInstructionValue(instr.value);
+  let value = printInstructionValue(instr.value);
+  if (instr.effects != null) {
+    value += `\n    ${instr.effects.map(printAliasingEffect).join('\n    ')}`;
+  }
 
   if (instr.lvalue !== null) {
     return `${id} ${printPlace(instr.lvalue)} = ${value}`;
@@ -213,6 +219,9 @@ export function printTerminal(terminal: Terminal): Array<string> | string {
       value = `[${terminal.id}] Return${
         terminal.value != null ? ' ' + printPlace(terminal.value) : ''
       }`;
+      if (terminal.effects != null) {
+        value += `\n    ${terminal.effects.map(printAliasingEffect).join('\n    ')}`;
+      }
       break;
     }
     case 'goto': {
@@ -281,6 +290,9 @@ export function printTerminal(terminal: Terminal): Array<string> | string {
     }
     case 'maybe-throw': {
       value = `[${terminal.id}] MaybeThrow continuation=bb${terminal.continuation} handler=bb${terminal.handler}`;
+      if (terminal.effects != null) {
+        value += `\n    ${terminal.effects.map(printAliasingEffect).join('\n    ')}`;
+      }
       break;
     }
     case 'scope': {
@@ -555,8 +567,11 @@ export function printInstructionValue(instrValue: ReactiveValue): string {
             }
           })
           .join(', ') ?? '';
-      const type = printType(instrValue.loweredFunc.func.returnType).trim();
-      value = `${kind} ${name} @context[${context}] @effects[${effects}]${type !== '' ? ` return${type}` : ''}:\n${fn}`;
+      const aliasingEffects =
+        instrValue.loweredFunc.func.aliasingEffects
+          ?.map(printAliasingEffect)
+          ?.join(', ') ?? '';
+      value = `${kind} ${name} @context[${context}] @effects[${effects}] @aliasingEffects=[${aliasingEffects}]\n${fn}`;
       break;
     }
     case 'TaggedTemplateExpression': {
@@ -922,3 +937,107 @@ function getFunctionName(
       return defaultValue;
   }
 }
+
+export function printAliasingEffect(effect: AliasingEffect): string {
+  switch (effect.kind) {
+    case 'Assign': {
+      return `Assign ${printPlaceForAliasEffect(effect.into)} = ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'Alias': {
+      return `Alias ${printPlaceForAliasEffect(effect.into)} = ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'Capture': {
+      return `Capture ${printPlaceForAliasEffect(effect.into)} <- ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'ImmutableCapture': {
+      return `ImmutableCapture ${printPlaceForAliasEffect(effect.into)} <- ${printPlaceForAliasEffect(effect.from)}`;
+    }
+    case 'Create': {
+      return `Create ${printPlaceForAliasEffect(effect.into)} = ${effect.value}`;
+    }
+    case 'CreateFrom': {
+      return `Create ${printPlaceForAliasEffect(effect.into)} = kindOf(${printPlaceForAliasEffect(effect.from)})`;
+    }
+    case 'CreateFunction': {
+      return `Function ${printPlaceForAliasEffect(effect.into)} = Function captures=[${effect.captures.map(printPlaceForAliasEffect).join(', ')}]`;
+    }
+    case 'Apply': {
+      const receiverCallee =
+        effect.receiver.identifier.id === effect.function.identifier.id
+          ? printPlaceForAliasEffect(effect.receiver)
+          : `${printPlaceForAliasEffect(effect.receiver)}.${printPlaceForAliasEffect(effect.function)}`;
+      const args = effect.args
+        .map(arg => {
+          if (arg.kind === 'Identifier') {
+            return printPlaceForAliasEffect(arg);
+          } else if (arg.kind === 'Hole') {
+            return ' ';
+          }
+          return `...${printPlaceForAliasEffect(arg.place)}`;
+        })
+        .join(', ');
+      let signature = '';
+      if (effect.signature != null) {
+        if (effect.signature.aliasing != null) {
+          signature = printAliasingSignature(effect.signature.aliasing);
+        } else {
+          signature = JSON.stringify(effect.signature, null, 2);
+        }
+      }
+      return `Apply ${printPlaceForAliasEffect(effect.into)} = ${receiverCallee}(${args})${signature != '' ? '\n     ' : ''}${signature}`;
+    }
+    case 'Freeze': {
+      return `Freeze ${printPlaceForAliasEffect(effect.value)} ${effect.reason}`;
+    }
+    case 'Mutate':
+    case 'MutateConditionally':
+    case 'MutateTransitive':
+    case 'MutateTransitiveConditionally': {
+      return `${effect.kind} ${printPlaceForAliasEffect(effect.value)}`;
+    }
+    case 'MutateFrozen': {
+      return `MutateFrozen ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+    }
+    case 'MutateGlobal': {
+      return `MutateGlobal ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+    }
+    case 'Impure': {
+      return `Impure ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+    }
+    case 'Render': {
+      return `Render ${printPlaceForAliasEffect(effect.place)}`;
+    }
+    default: {
+      assertExhaustive(effect, `Unexpected kind '${(effect as any).kind}'`);
+    }
+  }
+}
+
+function printPlaceForAliasEffect(place: Place): string {
+  return printIdentifier(place.identifier);
+}
+
+export function printAliasingSignature(signature: AliasingSignature): string {
+  const tokens: Array<string> = ['function '];
+  if (signature.temporaries.length !== 0) {
+    tokens.push('<');
+    tokens.push(
+      signature.temporaries.map(temp => `$${temp.identifier.id}`).join(', '),
+    );
+    tokens.push('>');
+  }
+  tokens.push('(');
+  tokens.push('this=$' + String(signature.receiver));
+  for (const param of signature.params) {
+    tokens.push(', $' + String(param));
+  }
+  if (signature.rest != null) {
+    tokens.push(`, ...$${String(signature.rest)}`);
+  }
+  tokens.push('): ');
+  tokens.push('$' + String(signature.returns) + ':');
+  for (const effect of signature.effects) {
+    tokens.push('\n  ' + printAliasingEffect(effect));
+  }
+  return tokens.join('');
+}

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

@@ -316,6 +316,7 @@ function collectTemporariesSidemapImpl(
         ) {
           temporaries.set(lvalue.identifier.id, {
             identifier: value.place.identifier,
+            reactive: value.place.reactive,
             path: [],
           });
         }
@@ -369,11 +370,13 @@ function getProperty(
   if (resolvedDependency == null) {
     property = {
       identifier: object.identifier,
+      reactive: object.reactive,
       path: [{property: propertyName, optional}],
     };
   } else {
     property = {
       identifier: resolvedDependency.identifier,
+      reactive: resolvedDependency.reactive,
       path: [...resolvedDependency.path, {property: propertyName, optional}],
     };
   }
@@ -532,6 +535,7 @@ export class DependencyCollectionContext {
     this.visitDependency(
       this.#temporaries.get(place.identifier.id) ?? {
         identifier: place.identifier,
+        reactive: place.reactive,
         path: [],
       },
     );
@@ -596,6 +600,7 @@ export class DependencyCollectionContext {
     ) {
       maybeDependency = {
         identifier: maybeDependency.identifier,
+        reactive: maybeDependency.reactive,
         path: [],
       };
     }
@@ -617,7 +622,11 @@ export class DependencyCollectionContext {
         identifier =>
           identifier.declarationId === place.identifier.declarationId,
       ) &&
-      this.#checkValidDependency({identifier: place.identifier, path: []})
+      this.#checkValidDependency({
+        identifier: place.identifier,
+        reactive: place.reactive,
+        path: [],
+      })
     ) {
       currentScope.reassignments.add(place.identifier);
     }

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

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

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

@@ -8,7 +8,12 @@
 import {isValidIdentifier} from '@babel/types';
 import {z} from 'zod';
 import {Effect, ValueKind} from '..';
-import {EffectSchema, ValueKindSchema} from './HIR';
+import {
+  EffectSchema,
+  ValueKindSchema,
+  ValueReason,
+  ValueReasonSchema,
+} from './HIR';
 
 export type ObjectPropertiesConfig = {[key: string]: TypeConfig};
 export const ObjectPropertiesSchema: z.ZodType<ObjectPropertiesConfig> = z
@@ -31,6 +36,194 @@ export const ObjectTypeSchema: z.ZodType<ObjectTypeConfig> = z.object({
   properties: ObjectPropertiesSchema.nullable(),
 });
 
+export const LifetimeIdSchema = z.string().refine(id => id.startsWith('@'), {
+  message: "Placeholder names must start with '@'",
+});
+
+export type FreezeEffectConfig = {
+  kind: 'Freeze';
+  value: string;
+  reason: ValueReason;
+};
+
+export const FreezeEffectSchema: z.ZodType<FreezeEffectConfig> = z.object({
+  kind: z.literal('Freeze'),
+  value: LifetimeIdSchema,
+  reason: ValueReasonSchema,
+});
+
+export type MutateEffectConfig = {
+  kind: 'Mutate';
+  value: string;
+};
+
+export const MutateEffectSchema: z.ZodType<MutateEffectConfig> = z.object({
+  kind: z.literal('Mutate'),
+  value: LifetimeIdSchema,
+});
+
+export type MutateTransitiveConditionallyConfig = {
+  kind: 'MutateTransitiveConditionally';
+  value: string;
+};
+
+export const MutateTransitiveConditionallySchema: z.ZodType<MutateTransitiveConditionallyConfig> =
+  z.object({
+    kind: z.literal('MutateTransitiveConditionally'),
+    value: LifetimeIdSchema,
+  });
+
+export type CreateEffectConfig = {
+  kind: 'Create';
+  into: string;
+  value: ValueKind;
+  reason: ValueReason;
+};
+
+export const CreateEffectSchema: z.ZodType<CreateEffectConfig> = z.object({
+  kind: z.literal('Create'),
+  into: LifetimeIdSchema,
+  value: ValueKindSchema,
+  reason: ValueReasonSchema,
+});
+
+export type AssignEffectConfig = {
+  kind: 'Assign';
+  from: string;
+  into: string;
+};
+
+export const AssignEffectSchema: z.ZodType<AssignEffectConfig> = z.object({
+  kind: z.literal('Assign'),
+  from: LifetimeIdSchema,
+  into: LifetimeIdSchema,
+});
+
+export type AliasEffectConfig = {
+  kind: 'Alias';
+  from: string;
+  into: string;
+};
+
+export const AliasEffectSchema: z.ZodType<AliasEffectConfig> = z.object({
+  kind: z.literal('Alias'),
+  from: LifetimeIdSchema,
+  into: LifetimeIdSchema,
+});
+
+export type CaptureEffectConfig = {
+  kind: 'Capture';
+  from: string;
+  into: string;
+};
+
+export const CaptureEffectSchema: z.ZodType<CaptureEffectConfig> = z.object({
+  kind: z.literal('Capture'),
+  from: LifetimeIdSchema,
+  into: LifetimeIdSchema,
+});
+
+export type CreateFromEffectConfig = {
+  kind: 'CreateFrom';
+  from: string;
+  into: string;
+};
+
+export const CreateFromEffectSchema: z.ZodType<CreateFromEffectConfig> =
+  z.object({
+    kind: z.literal('CreateFrom'),
+    from: LifetimeIdSchema,
+    into: LifetimeIdSchema,
+  });
+
+export type ApplyArgConfig =
+  | string
+  | {kind: 'Spread'; place: string}
+  | {kind: 'Hole'};
+
+export const ApplyArgSchema: z.ZodType<ApplyArgConfig> = z.union([
+  LifetimeIdSchema,
+  z.object({
+    kind: z.literal('Spread'),
+    place: LifetimeIdSchema,
+  }),
+  z.object({
+    kind: z.literal('Hole'),
+  }),
+]);
+
+export type ApplyEffectConfig = {
+  kind: 'Apply';
+  receiver: string;
+  function: string;
+  mutatesFunction: boolean;
+  args: Array<ApplyArgConfig>;
+  into: string;
+};
+
+export const ApplyEffectSchema: z.ZodType<ApplyEffectConfig> = z.object({
+  kind: z.literal('Apply'),
+  receiver: LifetimeIdSchema,
+  function: LifetimeIdSchema,
+  mutatesFunction: z.boolean(),
+  args: z.array(ApplyArgSchema),
+  into: LifetimeIdSchema,
+});
+
+export type ImpureEffectConfig = {
+  kind: 'Impure';
+  place: string;
+};
+
+export const ImpureEffectSchema: z.ZodType<ImpureEffectConfig> = z.object({
+  kind: z.literal('Impure'),
+  place: LifetimeIdSchema,
+});
+
+export type AliasingEffectConfig =
+  | FreezeEffectConfig
+  | CreateEffectConfig
+  | CreateFromEffectConfig
+  | AssignEffectConfig
+  | AliasEffectConfig
+  | CaptureEffectConfig
+  | ImpureEffectConfig
+  | MutateEffectConfig
+  | MutateTransitiveConditionallyConfig
+  | ApplyEffectConfig;
+
+export const AliasingEffectSchema: z.ZodType<AliasingEffectConfig> = z.union([
+  FreezeEffectSchema,
+  CreateEffectSchema,
+  CreateFromEffectSchema,
+  AssignEffectSchema,
+  AliasEffectSchema,
+  CaptureEffectSchema,
+  ImpureEffectSchema,
+  MutateEffectSchema,
+  MutateTransitiveConditionallySchema,
+  ApplyEffectSchema,
+]);
+
+export type AliasingSignatureConfig = {
+  receiver: string;
+  params: Array<string>;
+  rest: string | null;
+  returns: string;
+  effects: Array<AliasingEffectConfig>;
+  temporaries: Array<string>;
+};
+
+export const AliasingSignatureSchema: z.ZodType<AliasingSignatureConfig> =
+  z.object({
+    receiver: LifetimeIdSchema,
+    params: z.array(LifetimeIdSchema),
+    rest: LifetimeIdSchema.nullable(),
+    returns: LifetimeIdSchema,
+    effects: z.array(AliasingEffectSchema),
+    temporaries: z.array(LifetimeIdSchema),
+  });
+
 export type FunctionTypeConfig = {
   kind: 'function';
   positionalParams: Array<Effect>;
@@ -42,6 +235,7 @@ export type FunctionTypeConfig = {
   mutableOnlyIfOperandsAreMutable?: boolean | null | undefined;
   impure?: boolean | null | undefined;
   canonicalName?: string | null | undefined;
+  aliasing?: AliasingSignatureConfig | null | undefined;
 };
 export const FunctionTypeSchema: z.ZodType<FunctionTypeConfig> = z.object({
   kind: z.literal('function'),
@@ -54,6 +248,7 @@ export const FunctionTypeSchema: z.ZodType<FunctionTypeConfig> = z.object({
   mutableOnlyIfOperandsAreMutable: z.boolean().nullable().optional(),
   impure: z.boolean().nullable().optional(),
   canonicalName: z.string().nullable().optional(),
+  aliasing: AliasingSignatureSchema.nullable().optional(),
 });
 
 export type HookTypeConfig = {
@@ -63,6 +258,7 @@ export type HookTypeConfig = {
   returnType: TypeConfig;
   returnValueKind?: ValueKind | null | undefined;
   noAlias?: boolean | null | undefined;
+  aliasing?: AliasingSignatureConfig | null | undefined;
 };
 export const HookTypeSchema: z.ZodType<HookTypeConfig> = z.object({
   kind: z.literal('hook'),
@@ -71,6 +267,7 @@ export const HookTypeSchema: z.ZodType<HookTypeConfig> = z.object({
   returnType: z.lazy(() => TypeSchema),
   returnValueKind: ValueKindSchema.nullable().optional(),
   noAlias: z.boolean().nullable().optional(),
+  aliasing: AliasingSignatureSchema.nullable().optional(),
 });
 
 export type BuiltInTypeConfig =

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

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

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

@@ -0,0 +1,244 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+import {CompilerErrorDetailOptions} from '../CompilerError';
+import {
+  FunctionExpression,
+  GeneratedSource,
+  Hole,
+  IdentifierId,
+  ObjectMethod,
+  Place,
+  SourceLocation,
+  SpreadPattern,
+  ValueKind,
+  ValueReason,
+} from '../HIR';
+import {FunctionSignature} from '../HIR/ObjectShape';
+import {printSourceLocation} from '../HIR/PrintHIR';
+
+/**
+ * `AliasingEffect` describes a set of "effects" that an instruction/terminal has on one or
+ * more values in a program. These effects include mutation of values, freezing values,
+ * tracking data flow between values, and other specialized cases.
+ */
+export type AliasingEffect =
+  /**
+   * Marks the given value and its direct aliases as frozen.
+   *
+   * Captured values are *not* considered frozen, because we cannot be sure that a previously
+   * captured value will still be captured at the point of the freeze.
+   *
+   * For example:
+   * const x = {};
+   * const y = [x];
+   * y.pop(); // y dosn't contain x anymore!
+   * freeze(y);
+   * mutate(x); // safe to mutate!
+   *
+   * The exception to this is FunctionExpressions - since it is impossible to change which
+   * value a function closes over[1] we can transitively freeze functions and their captures.
+   *
+   * [1] Except for `let` values that are reassigned and closed over by a function, but we
+   * handle this explicitly with StoreContext/LoadContext.
+   */
+  | {kind: 'Freeze'; value: Place; reason: ValueReason}
+  /**
+   * Mutate the value and any direct aliases (not captures). Errors if the value is not mutable.
+   */
+  | {kind: 'Mutate'; value: Place}
+  /**
+   * Mutate the value and any direct aliases (not captures), but only if the value is known mutable.
+   * This should be rare.
+   *
+   * TODO: this is only used for IteratorNext, but even then MutateTransitiveConditionally is more
+   * correct for iterators of unknown types.
+   */
+  | {kind: 'MutateConditionally'; value: Place}
+  /**
+   * Mutate the value, any direct aliases, and any transitive captures. Errors if the value is not mutable.
+   */
+  | {kind: 'MutateTransitive'; value: Place}
+  /**
+   * Mutates any of the value, its direct aliases, and its transitive captures that are mutable.
+   */
+  | {kind: 'MutateTransitiveConditionally'; value: Place}
+  /**
+   * Records information flow from `from` to `into` in cases where local mutation of the destination
+   * will *not* mutate the source:
+   *
+   * - Capture a -> b and Mutate(b) X=> (does not imply) Mutate(a)
+   * - Capture a -> b and MutateTransitive(b) => (does imply) Mutate(a)
+   *
+   * Example: `array.push(item)`. Information from item is captured into array, but there is not a
+   * direct aliasing, and local mutations of array will not modify item.
+   */
+  | {kind: 'Capture'; from: Place; into: Place}
+  /**
+   * Records information flow from `from` to `into` in cases where local mutation of the destination
+   * *will* mutate the source:
+   *
+   * - Alias a -> b and Mutate(b) => (does imply) Mutate(a)
+   * - Alias a -> b and MutateTransitive(b) => (does imply) Mutate(a)
+   *
+   * Example: `c = identity(a)`. We don't know what `identity()` returns so we can't use Assign.
+   * But we have to assume that it _could_ be returning its input, such that a local mutation of
+   * c could be mutating a.
+   */
+  | {kind: 'Alias'; from: Place; into: Place}
+  /**
+   * Records direct assignment: `into = from`.
+   */
+  | {kind: 'Assign'; from: Place; into: Place}
+  /**
+   * Creates a value of the given type at the given place
+   */
+  | {kind: 'Create'; into: Place; value: ValueKind; reason: ValueReason}
+  /**
+   * Creates a new value with the same kind as the starting value.
+   */
+  | {kind: 'CreateFrom'; from: Place; into: Place}
+  /**
+   * Immutable data flow, used for escape analysis. Does not influence mutable range analysis:
+   */
+  | {kind: 'ImmutableCapture'; from: Place; into: Place}
+  /**
+   * Calls the function at the given place with the given arguments either captured or aliased,
+   * and captures/aliases the result into the given place.
+   */
+  | {
+      kind: 'Apply';
+      receiver: Place;
+      function: Place;
+      mutatesFunction: boolean;
+      args: Array<Place | SpreadPattern | Hole>;
+      into: Place;
+      signature: FunctionSignature | null;
+      loc: SourceLocation;
+    }
+  /**
+   * Constructs a function value with the given captures. The mutability of the function
+   * will be determined by the mutability of the capture values when evaluated.
+   */
+  | {
+      kind: 'CreateFunction';
+      captures: Array<Place>;
+      function: FunctionExpression | ObjectMethod;
+      into: Place;
+    }
+  /**
+   * Mutation of a value known to be immutable
+   */
+  | {kind: 'MutateFrozen'; place: Place; error: CompilerErrorDetailOptions}
+  /**
+   * Mutation of a global
+   */
+  | {
+      kind: 'MutateGlobal';
+      place: Place;
+      error: CompilerErrorDetailOptions;
+    }
+  /**
+   * Indicates a side-effect that is not safe during render
+   */
+  | {kind: 'Impure'; place: Place; error: CompilerErrorDetailOptions}
+  /**
+   * Indicates that a given place is accessed during render. Used to distingush
+   * hook arguments that are known to be called immediately vs those used for
+   * event handlers/effects, and for JSX values known to be called during render
+   * (tags, children) vs those that may be events/effect (other props).
+   */
+  | {
+      kind: 'Render';
+      place: Place;
+    };
+
+export function hashEffect(effect: AliasingEffect): string {
+  switch (effect.kind) {
+    case 'Apply': {
+      return [
+        effect.kind,
+        effect.receiver.identifier.id,
+        effect.function.identifier.id,
+        effect.mutatesFunction,
+        effect.args
+          .map(a => {
+            if (a.kind === 'Hole') {
+              return '';
+            } else if (a.kind === 'Identifier') {
+              return a.identifier.id;
+            } else {
+              return `...${a.place.identifier.id}`;
+            }
+          })
+          .join(','),
+        effect.into.identifier.id,
+      ].join(':');
+    }
+    case 'CreateFrom':
+    case 'ImmutableCapture':
+    case 'Assign':
+    case 'Alias':
+    case 'Capture': {
+      return [
+        effect.kind,
+        effect.from.identifier.id,
+        effect.into.identifier.id,
+      ].join(':');
+    }
+    case 'Create': {
+      return [
+        effect.kind,
+        effect.into.identifier.id,
+        effect.value,
+        effect.reason,
+      ].join(':');
+    }
+    case 'Freeze': {
+      return [effect.kind, effect.value.identifier.id, effect.reason].join(':');
+    }
+    case 'Impure':
+    case 'Render': {
+      return [effect.kind, effect.place.identifier.id].join(':');
+    }
+    case 'MutateFrozen':
+    case 'MutateGlobal': {
+      return [
+        effect.kind,
+        effect.place.identifier.id,
+        effect.error.severity,
+        effect.error.reason,
+        effect.error.description,
+        printSourceLocation(effect.error.loc ?? GeneratedSource),
+      ].join(':');
+    }
+    case 'Mutate':
+    case 'MutateConditionally':
+    case 'MutateTransitive':
+    case 'MutateTransitiveConditionally': {
+      return [effect.kind, effect.value.identifier.id].join(':');
+    }
+    case 'CreateFunction': {
+      return [
+        effect.kind,
+        effect.into.identifier.id,
+        // return places are a unique way to identify functions themselves
+        effect.function.loweredFunc.func.returns.identifier.id,
+        effect.captures.map(p => p.identifier.id).join(','),
+      ].join(':');
+    }
+  }
+}
+
+export type AliasingSignature = {
+  receiver: IdentifierId;
+  params: Array<IdentifierId>;
+  rest: IdentifierId | null;
+  returns: IdentifierId;
+  effects: Array<AliasingEffect>;
+  temporaries: Array<Place>;
+};

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

@@ -10,6 +10,7 @@ import {
   Effect,
   HIRFunction,
   Identifier,
+  IdentifierId,
   LoweredFunction,
   isRefOrRefValue,
   makeInstructionId,
@@ -19,6 +20,9 @@ import {inferReactiveScopeVariables} from '../ReactiveScopes';
 import {rewriteInstructionKindsBasedOnReassignment} from '../SSA';
 import {inferMutableRanges} from './InferMutableRanges';
 import inferReferenceEffects from './InferReferenceEffects';
+import {assertExhaustive} from '../Utils/utils';
+import {inferMutationAliasingEffects} from './InferMutationAliasingEffects';
+import {inferMutationAliasingRanges} from './InferMutationAliasingRanges';
 
 export default function analyseFunctions(func: HIRFunction): void {
   for (const [_, block] of func.body.blocks) {
@@ -26,15 +30,27 @@ export default function analyseFunctions(func: HIRFunction): void {
       switch (instr.value.kind) {
         case 'ObjectMethod':
         case 'FunctionExpression': {
-          lower(instr.value.loweredFunc.func);
-          infer(instr.value.loweredFunc);
+          if (!func.env.config.enableNewMutationAliasingModel) {
+            lower(instr.value.loweredFunc.func);
+            infer(instr.value.loweredFunc);
+          } else {
+            lowerWithMutationAliasing(instr.value.loweredFunc.func);
+          }
 
           /**
            * Reset mutable range for outer inferReferenceEffects
            */
           for (const operand of instr.value.loweredFunc.func.context) {
-            operand.identifier.mutableRange.start = makeInstructionId(0);
-            operand.identifier.mutableRange.end = makeInstructionId(0);
+            /**
+             * NOTE: inferReactiveScopeVariables makes identifiers in the scope
+             * point to the *same* mutableRange instance. Resetting start/end
+             * here is insufficient, because a later mutation of the range
+             * for any one identifier could affect the range for other identifiers.
+             */
+            operand.identifier.mutableRange = {
+              start: makeInstructionId(0),
+              end: makeInstructionId(0),
+            };
             operand.identifier.scope = null;
           }
           break;
@@ -44,6 +60,86 @@ export default function analyseFunctions(func: HIRFunction): void {
   }
 }
 
+function lowerWithMutationAliasing(fn: HIRFunction): void {
+  /**
+   * Phase 1: similar to lower(), but using the new mutation/aliasing inference
+   */
+  analyseFunctions(fn);
+  inferMutationAliasingEffects(fn, {isFunctionExpression: true});
+  deadCodeElimination(fn);
+  const functionEffects = inferMutationAliasingRanges(fn, {
+    isFunctionExpression: true,
+  }).unwrap();
+  rewriteInstructionKindsBasedOnReassignment(fn);
+  inferReactiveScopeVariables(fn);
+  fn.aliasingEffects = functionEffects;
+
+  /**
+   * Phase 2: populate the Effect of each context variable to use in inferring
+   * the outer function. For example, InferMutationAliasingEffects uses context variable
+   * effects to decide if the function may be mutable or not.
+   */
+  const capturedOrMutated = new Set<IdentifierId>();
+  for (const effect of functionEffects) {
+    switch (effect.kind) {
+      case 'Assign':
+      case 'Alias':
+      case 'Capture':
+      case 'CreateFrom': {
+        capturedOrMutated.add(effect.from.identifier.id);
+        break;
+      }
+      case 'Apply': {
+        CompilerError.invariant(false, {
+          reason: `[AnalyzeFunctions] Expected Apply effects to be replaced with more precise effects`,
+          loc: effect.function.loc,
+        });
+      }
+      case 'Mutate':
+      case 'MutateConditionally':
+      case 'MutateTransitive':
+      case 'MutateTransitiveConditionally': {
+        capturedOrMutated.add(effect.value.identifier.id);
+        break;
+      }
+      case 'Impure':
+      case 'Render':
+      case 'MutateFrozen':
+      case 'MutateGlobal':
+      case 'CreateFunction':
+      case 'Create':
+      case 'Freeze':
+      case 'ImmutableCapture': {
+        // no-op
+        break;
+      }
+      default: {
+        assertExhaustive(
+          effect,
+          `Unexpected effect kind ${(effect as any).kind}`,
+        );
+      }
+    }
+  }
+
+  for (const operand of fn.context) {
+    if (
+      capturedOrMutated.has(operand.identifier.id) ||
+      operand.effect === Effect.Capture
+    ) {
+      operand.effect = Effect.Capture;
+    } else {
+      operand.effect = Effect.Read;
+    }
+  }
+
+  fn.env.logger?.debugLogIRs?.({
+    kind: 'hir',
+    name: 'AnalyseFunction (inner)',
+    value: fn,
+  });
+}
+
 function lower(func: HIRFunction): void {
   analyseFunctions(func);
   inferReferenceEffects(func, {isFunctionExpression: true});

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

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

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

@@ -10,7 +10,6 @@ import {CompilerError, SourceLocation} from '..';
 import {
   ArrayExpression,
   Effect,
-  Environment,
   FunctionExpression,
   GeneratedSource,
   HIRFunction,
@@ -29,6 +28,10 @@ import {
   isSetStateType,
   isFireFunctionType,
   makeScopeId,
+  HIR,
+  BasicBlock,
+  BlockId,
+  isEffectEventFunctionType,
 } from '../HIR';
 import {collectHoistablePropertyLoadsInInnerFn} from '../HIR/CollectHoistablePropertyLoads';
 import {collectOptionalChainSidemap} from '../HIR/CollectOptionalChainDependencies';
@@ -38,13 +41,20 @@ import {
   createTemporaryPlace,
   fixScopeAndIdentifierRanges,
   markInstructionIds,
+  markPredecessors,
+  reversePostorderBlocks,
 } from '../HIR/HIRBuilder';
 import {
   collectTemporariesSidemap,
   DependencyCollectionContext,
   handleInstruction,
 } from '../HIR/PropagateScopeDependenciesHIR';
-import {eachInstructionOperand, eachTerminalOperand} from '../HIR/visitors';
+import {buildDependencyInstructions} from '../HIR/ScopeDependencyUtils';
+import {
+  eachInstructionOperand,
+  eachTerminalOperand,
+  terminalFallthrough,
+} from '../HIR/visitors';
 import {empty} from '../Utils/Stack';
 import {getOrInsertWith} from '../Utils/utils';
 
@@ -53,7 +63,6 @@ import {getOrInsertWith} from '../Utils/utils';
  * a second argument to the useEffect call if no dependency array is provided.
  */
 export function inferEffectDependencies(fn: HIRFunction): void {
-  let hasRewrite = false;
   const fnExpressions = new Map<
     IdentifierId,
     TInstruction<FunctionExpression>
@@ -86,6 +95,7 @@ export function inferEffectDependencies(fn: HIRFunction): void {
    * reactive(Identifier i) = Union_{reference of i}(reactive(reference))
    */
   const reactiveIds = inferReactiveIdentifiers(fn);
+  const rewriteBlocks: Array<BasicBlock> = [];
 
   for (const [, block] of fn.body.blocks) {
     if (block.terminal.kind === 'scope') {
@@ -101,7 +111,7 @@ export function inferEffectDependencies(fn: HIRFunction): void {
         );
       }
     }
-    const rewriteInstrs = new Map<InstructionId, Array<Instruction>>();
+    const rewriteInstrs: Array<SpliceInfo> = [];
     for (const instr of block.instructions) {
       const {value, lvalue} = instr;
       if (value.kind === 'FunctionExpression') {
@@ -165,7 +175,6 @@ export function inferEffectDependencies(fn: HIRFunction): void {
         ) {
           // We have a useEffect call with no deps array, so we need to infer the deps
           const effectDeps: Array<Place> = [];
-          const newInstructions: Array<Instruction> = [];
           const deps: ArrayExpression = {
             kind: 'ArrayExpression',
             elements: effectDeps,
@@ -196,24 +205,29 @@ export function inferEffectDependencies(fn: HIRFunction): void {
              */
 
             const usedDeps = [];
-            for (const dep of minimalDeps) {
+            for (const maybeDep of minimalDeps) {
               if (
-                ((isUseRefType(dep.identifier) ||
-                  isSetStateType(dep.identifier)) &&
-                  !reactiveIds.has(dep.identifier.id)) ||
-                isFireFunctionType(dep.identifier)
+                ((isUseRefType(maybeDep.identifier) ||
+                  isSetStateType(maybeDep.identifier)) &&
+                  !reactiveIds.has(maybeDep.identifier.id)) ||
+                isFireFunctionType(maybeDep.identifier) ||
+                isEffectEventFunctionType(maybeDep.identifier)
               ) {
                 // exclude non-reactive hook results, which will never be in a memo block
                 continue;
               }
 
-              const {place, instructions} = writeDependencyToInstructions(
+              const dep = truncateDepAtCurrent(maybeDep);
+              const {place, value, exitBlockId} = buildDependencyInstructions(
                 dep,
-                reactiveIds.has(dep.identifier.id),
                 fn.env,
-                fnExpr.loc,
               );
-              newInstructions.push(...instructions);
+              rewriteInstrs.push({
+                kind: 'block',
+                location: instr.id,
+                value,
+                exitBlockId: exitBlockId,
+              });
               effectDeps.push(place);
               usedDeps.push(dep);
             }
@@ -234,27 +248,34 @@ export function inferEffectDependencies(fn: HIRFunction): void {
               });
             }
 
-            newInstructions.push({
-              id: makeInstructionId(0),
-              loc: GeneratedSource,
-              lvalue: {...depsPlace, effect: Effect.Mutate},
-              value: deps,
-            });
-
             // Step 2: push the inferred deps array as an argument of the useEffect
+            rewriteInstrs.push({
+              kind: 'instr',
+              location: instr.id,
+              value: {
+                id: makeInstructionId(0),
+                loc: GeneratedSource,
+                lvalue: {...depsPlace, effect: Effect.Mutate},
+                value: deps,
+                effects: null,
+              },
+            });
             value.args.push({...depsPlace, effect: Effect.Freeze});
-            rewriteInstrs.set(instr.id, newInstructions);
             fn.env.inferredEffectLocations.add(callee.loc);
           } else if (loadGlobals.has(value.args[0].identifier.id)) {
             // Global functions have no reactive dependencies, so we can insert an empty array
-            newInstructions.push({
-              id: makeInstructionId(0),
-              loc: GeneratedSource,
-              lvalue: {...depsPlace, effect: Effect.Mutate},
-              value: deps,
+            rewriteInstrs.push({
+              kind: 'instr',
+              location: instr.id,
+              value: {
+                id: makeInstructionId(0),
+                loc: GeneratedSource,
+                lvalue: {...depsPlace, effect: Effect.Mutate},
+                value: deps,
+                effects: null,
+              },
             });
             value.args.push({...depsPlace, effect: Effect.Freeze});
-            rewriteInstrs.set(instr.id, newInstructions);
             fn.env.inferredEffectLocations.add(callee.loc);
           }
         } else if (
@@ -285,85 +306,164 @@ export function inferEffectDependencies(fn: HIRFunction): void {
         }
       }
     }
-    if (rewriteInstrs.size > 0) {
-      hasRewrite = true;
-      const newInstrs = [];
-      for (const instr of block.instructions) {
-        const newInstr = rewriteInstrs.get(instr.id);
-        if (newInstr != null) {
-          newInstrs.push(...newInstr, instr);
-        } else {
-          newInstrs.push(instr);
-        }
-      }
-      block.instructions = newInstrs;
-    }
+    rewriteSplices(block, rewriteInstrs, rewriteBlocks);
   }
-  if (hasRewrite) {
+
+  if (rewriteBlocks.length > 0) {
+    for (const block of rewriteBlocks) {
+      fn.body.blocks.set(block.id, block);
+    }
+
+    /**
+     * Fixup the HIR to restore RPO, ensure correct predecessors, and renumber
+     * instructions.
+     */
+    reversePostorderBlocks(fn.body);
+    markPredecessors(fn.body);
     // Renumber instructions and fix scope ranges
     markInstructionIds(fn.body);
     fixScopeAndIdentifierRanges(fn.body);
+
     fn.env.hasInferredEffect = true;
   }
 }
 
-function writeDependencyToInstructions(
+function truncateDepAtCurrent(
   dep: ReactiveScopeDependency,
-  reactive: boolean,
-  env: Environment,
-  loc: SourceLocation,
-): {place: Place; instructions: Array<Instruction>} {
-  const instructions: Array<Instruction> = [];
-  let currValue = createTemporaryPlace(env, GeneratedSource);
-  currValue.reactive = reactive;
-  instructions.push({
-    id: makeInstructionId(0),
-    loc: GeneratedSource,
-    lvalue: {...currValue, effect: Effect.Mutate},
-    value: {
-      kind: 'LoadLocal',
-      place: {
-        kind: 'Identifier',
-        identifier: dep.identifier,
-        effect: Effect.Capture,
-        reactive,
-        loc: loc,
-      },
-      loc: loc,
-    },
-  });
-  for (const path of dep.path) {
-    if (path.optional) {
-      /**
-       * TODO: instead of truncating optional paths, reuse
-       * instructions from hoisted dependencies block(s)
-       */
-      break;
-    }
-    if (path.property === 'current') {
-      /*
-       * Prune ref.current accesses. This may over-capture for non-ref values with
-       * a current property, but that's fine.
-       */
-      break;
-    }
-    const nextValue = createTemporaryPlace(env, GeneratedSource);
-    nextValue.reactive = reactive;
-    instructions.push({
-      id: makeInstructionId(0),
-      loc: GeneratedSource,
-      lvalue: {...nextValue, effect: Effect.Mutate},
-      value: {
-        kind: 'PropertyLoad',
-        object: {...currValue, effect: Effect.Capture},
-        property: path.property,
-        loc: loc,
-      },
-    });
-    currValue = nextValue;
+): ReactiveScopeDependency {
+  const idx = dep.path.findIndex(path => path.property === 'current');
+  if (idx === -1) {
+    return dep;
+  } else {
+    return {...dep, path: dep.path.slice(0, idx)};
   }
-  currValue.effect = Effect.Freeze;
-  return {place: currValue, instructions};
+}
+
+type SpliceInfo =
+  | {kind: 'instr'; location: InstructionId; value: Instruction}
+  | {
+      kind: 'block';
+      location: InstructionId;
+      value: HIR;
+      exitBlockId: BlockId;
+    };
+
+function rewriteSplices(
+  originalBlock: BasicBlock,
+  splices: Array<SpliceInfo>,
+  rewriteBlocks: Array<BasicBlock>,
+): void {
+  if (splices.length === 0) {
+    return;
+  }
+  /**
+   * Splice instructions or value blocks into the original block.
+   * --- original block ---
+   * bb_original
+   *   instr1
+   *   ...
+   *   instr2 <-- splice location
+   *   instr3
+   *   ...
+   *   <original terminal>
+   *
+   * If there is more than one block in the splice, this means that we're
+   * splicing in a set of value-blocks of the following structure:
+   * --- blocks we're splicing in ---
+   * bb_entry:
+   *   instrEntry
+   *   ...
+   *   <splice terminal> fallthrough=bb_exit
+   *
+   * bb1(value):
+   *   ...
+   *
+   * bb_exit:
+   *   instrExit
+   *   ...
+   *   <synthetic terminal>
+   *
+   *
+   * --- rewritten blocks ---
+   * bb_original
+   *   instr1
+   *   ... (original instructions)
+   *   instr2
+   *   instrEntry
+   *   ... (spliced instructions)
+   *   <splice terminal> fallthrough=bb_exit
+   *
+   * bb1(value):
+   *   ...
+   *
+   * bb_exit:
+   *   instrExit
+   *   ... (spliced instructions)
+   *   instr3
+   *   ... (original instructions)
+   *   <original terminal>
+   */
+  const originalInstrs = originalBlock.instructions;
+  let currBlock: BasicBlock = {...originalBlock, instructions: []};
+  rewriteBlocks.push(currBlock);
+
+  let cursor = 0;
+  for (const rewrite of splices) {
+    while (originalInstrs[cursor].id < rewrite.location) {
+      CompilerError.invariant(
+        originalInstrs[cursor].id < originalInstrs[cursor + 1].id,
+        {
+          reason:
+            '[InferEffectDependencies] Internal invariant broken: expected block instructions to be sorted',
+          loc: originalInstrs[cursor].loc,
+        },
+      );
+      currBlock.instructions.push(originalInstrs[cursor]);
+      cursor++;
+    }
+    CompilerError.invariant(originalInstrs[cursor].id === rewrite.location, {
+      reason:
+        '[InferEffectDependencies] Internal invariant broken: splice location not found',
+      loc: originalInstrs[cursor].loc,
+    });
+
+    if (rewrite.kind === 'instr') {
+      currBlock.instructions.push(rewrite.value);
+    } else {
+      const {entry, blocks} = rewrite.value;
+      const entryBlock = blocks.get(entry)!;
+      // splice in all instructions from the entry block
+      currBlock.instructions.push(...entryBlock.instructions);
+      if (blocks.size > 1) {
+        /**
+         * We're splicing in a set of value-blocks, which means we need
+         * to push new blocks and update terminals.
+         */
+        CompilerError.invariant(
+          terminalFallthrough(entryBlock.terminal) === rewrite.exitBlockId,
+          {
+            reason:
+              '[InferEffectDependencies] Internal invariant broken: expected entry block to have a fallthrough',
+            loc: entryBlock.terminal.loc,
+          },
+        );
+        const originalTerminal = currBlock.terminal;
+        currBlock.terminal = entryBlock.terminal;
+
+        for (const [id, block] of blocks) {
+          if (id === entry) {
+            continue;
+          }
+          if (id === rewrite.exitBlockId) {
+            block.terminal = originalTerminal;
+            currBlock = block;
+          }
+          rewriteBlocks.push(block);
+        }
+      }
+    }
+  }
+  currBlock.instructions.push(...originalInstrs.slice(cursor));
 }
 
 function inferReactiveIdentifiers(fn: HIRFunction): Set<IdentifierId> {

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

@@ -324,7 +324,7 @@ function isEffectSafeOutsideRender(effect: FunctionEffect): boolean {
   return effect.kind === 'GlobalMutation';
 }
 
-function getWriteErrorReason(abstractValue: AbstractValue): string {
+export function getWriteErrorReason(abstractValue: AbstractValue): string {
   if (abstractValue.reason.has(ValueReason.Global)) {
     return 'Writing to a variable defined outside a component or hook is not allowed. Consider using an effect';
   } else if (abstractValue.reason.has(ValueReason.JsxCaptured)) {
@@ -339,6 +339,12 @@ function getWriteErrorReason(abstractValue: AbstractValue): string {
     return "Mutating a value returned from 'useState()', which should not be mutated. Use the setter function to update instead";
   } else if (abstractValue.reason.has(ValueReason.ReducerState)) {
     return "Mutating a value returned from 'useReducer()', which should not be mutated. Use the dispatch function to update instead";
+  } else if (abstractValue.reason.has(ValueReason.Effect)) {
+    return 'Updating a value used previously in an effect function or as an effect dependency is not allowed. Consider moving the mutation before calling useEffect()';
+  } else if (abstractValue.reason.has(ValueReason.HookCaptured)) {
+    return 'Updating a value previously passed as an argument to a hook is not allowed. Consider moving the mutation before calling the hook';
+  } else if (abstractValue.reason.has(ValueReason.HookReturn)) {
+    return 'Updating a value returned from a hook is not allowed. Consider moving the mutation into the hook where the value is constructed';
   } else {
     return 'This mutates a variable that React considers immutable';
   }

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

@@ -86,7 +86,7 @@ export function inferMutableRanges(ir: HIRFunction): void {
   }
 }
 
-function areEqualMaps<T>(a: Map<T, T>, b: Map<T, T>): boolean {
+function areEqualMaps<T, U>(a: Map<T, U>, b: Map<T, U>): boolean {
   if (a.size !== b.size) {
     return false;
   }

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

@@ -0,0 +1,766 @@
+/**
+ * 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, SourceLocation} from '..';
+import {
+  BlockId,
+  Effect,
+  HIRFunction,
+  Identifier,
+  IdentifierId,
+  InstructionId,
+  isJsxType,
+  makeInstructionId,
+  ValueKind,
+  ValueReason,
+  Place,
+  isPrimitiveType,
+} from '../HIR/HIR';
+import {
+  eachInstructionLValue,
+  eachInstructionValueOperand,
+  eachTerminalOperand,
+} from '../HIR/visitors';
+import {assertExhaustive, getOrInsertWith} from '../Utils/utils';
+import {Err, Ok, Result} from '../Utils/Result';
+import {AliasingEffect} from './AliasingEffects';
+
+/**
+ * This pass builds an abstract model of the heap and interprets the effects of the
+ * given function in order to determine the following:
+ * - The mutable ranges of all identifiers in the function
+ * - The externally-visible effects of the function, such as mutations of params and
+ *   context-vars, aliasing between params/context-vars/return-value, and impure side
+ *   effects.
+ * - The legacy `Effect` to store on each Place.
+ *
+ * This pass builds a data flow graph using the effects, tracking an abstract notion
+ * of "when" each effect occurs relative to the others. It then walks each mutation
+ * effect against the graph, updating the range of each node that would be reachable
+ * at the "time" that the effect occurred.
+ *
+ * This pass also validates against invalid effects: any function that is reachable
+ * by being called, or via a Render effect, is validated against mutating globals
+ * or calling impure code.
+ *
+ * Note that this function also populates the outer function's aliasing effects with
+ * any mutations that apply to its params or context variables.
+ *
+ * ## Example
+ * A function expression such as the following:
+ *
+ * ```
+ * (x) => { x.y = true }
+ * ```
+ *
+ * Would populate a `Mutate x` aliasing effect on the outer function.
+ *
+ * ## Returned Function Effects
+ *
+ * The function returns (if successful) a list of externally-visible effects.
+ * This is determined by simulating a conditional, transitive mutation against
+ * each param, context variable, and return value in turn, and seeing which other
+ * such values are affected. If they're affected, they must be captured, so we
+ * record a Capture.
+ *
+ * The only tricky bit is the return value, which could _alias_ (or even assign)
+ * one or more of the params/context-vars rather than just capturing. So we have
+ * to do a bit more tracking for returns.
+ */
+export function inferMutationAliasingRanges(
+  fn: HIRFunction,
+  {isFunctionExpression}: {isFunctionExpression: boolean},
+): Result<Array<AliasingEffect>, CompilerError> {
+  // The set of externally-visible effects
+  const functionEffects: Array<AliasingEffect> = [];
+
+  /**
+   * Part 1: Infer mutable ranges for values. We build an abstract model of
+   * values, the alias/capture edges between them, and the set of mutations.
+   * Edges and mutations are ordered, with mutations processed against the
+   * abstract model only after it is fully constructed by visiting all blocks
+   * _and_ connecting phis. Phis are considered ordered at the time of the
+   * phi node.
+   *
+   * This should (may?) mean that mutations are able to see the full state
+   * of the graph and mark all the appropriate identifiers as mutated at
+   * the correct point, accounting for both backward and forward edges.
+   * Ie a mutation of x accounts for both values that flowed into x,
+   * and values that x flowed into.
+   */
+  const state = new AliasingState();
+  type PendingPhiOperand = {from: Place; into: Place; index: number};
+  const pendingPhis = new Map<BlockId, Array<PendingPhiOperand>>();
+  const mutations: Array<{
+    index: number;
+    id: InstructionId;
+    transitive: boolean;
+    kind: MutationKind;
+    place: Place;
+  }> = [];
+  const renders: Array<{index: number; place: Place}> = [];
+
+  let index = 0;
+
+  const errors = new CompilerError();
+
+  for (const param of [...fn.params, ...fn.context, fn.returns]) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    state.create(place, {kind: 'Object'});
+  }
+  const seenBlocks = new Set<BlockId>();
+  for (const block of fn.body.blocks.values()) {
+    for (const phi of block.phis) {
+      state.create(phi.place, {kind: 'Phi'});
+      for (const [pred, operand] of phi.operands) {
+        if (!seenBlocks.has(pred)) {
+          // NOTE: annotation required to actually typecheck and not silently infer `any`
+          const blockPhis = getOrInsertWith<BlockId, Array<PendingPhiOperand>>(
+            pendingPhis,
+            pred,
+            () => [],
+          );
+          blockPhis.push({from: operand, into: phi.place, index: index++});
+        } else {
+          state.assign(index++, operand, phi.place);
+        }
+      }
+    }
+    seenBlocks.add(block.id);
+
+    for (const instr of block.instructions) {
+      if (instr.effects == null) continue;
+      for (const effect of instr.effects) {
+        if (effect.kind === 'Create') {
+          state.create(effect.into, {kind: 'Object'});
+        } else if (effect.kind === 'CreateFunction') {
+          state.create(effect.into, {
+            kind: 'Function',
+            function: effect.function.loweredFunc.func,
+          });
+        } else if (effect.kind === 'CreateFrom') {
+          state.createFrom(index++, effect.from, effect.into);
+        } else if (effect.kind === 'Assign') {
+          /**
+           * TODO: Invariant that the node is not initialized yet
+           *
+           * InferFunctionExpressionAliasingEffectSignatures currently infers
+           * Assign effects in some places that should be Alias, leading to
+           * Assign effects that reinitialize a value. The end result appears to
+           * be fine, but we should fix that inference pass so that we add the
+           * invariant here.
+           */
+          if (!state.nodes.has(effect.into.identifier)) {
+            state.create(effect.into, {kind: 'Object'});
+          }
+          state.assign(index++, effect.from, effect.into);
+        } else if (effect.kind === 'Alias') {
+          state.assign(index++, effect.from, effect.into);
+        } else if (effect.kind === 'Capture') {
+          state.capture(index++, effect.from, effect.into);
+        } else if (
+          effect.kind === 'MutateTransitive' ||
+          effect.kind === 'MutateTransitiveConditionally'
+        ) {
+          mutations.push({
+            index: index++,
+            id: instr.id,
+            transitive: true,
+            kind:
+              effect.kind === 'MutateTransitive'
+                ? MutationKind.Definite
+                : MutationKind.Conditional,
+            place: effect.value,
+          });
+        } else if (
+          effect.kind === 'Mutate' ||
+          effect.kind === 'MutateConditionally'
+        ) {
+          mutations.push({
+            index: index++,
+            id: instr.id,
+            transitive: false,
+            kind:
+              effect.kind === 'Mutate'
+                ? MutationKind.Definite
+                : MutationKind.Conditional,
+            place: effect.value,
+          });
+        } else if (
+          effect.kind === 'MutateFrozen' ||
+          effect.kind === 'MutateGlobal' ||
+          effect.kind === 'Impure'
+        ) {
+          errors.push(effect.error);
+          functionEffects.push(effect);
+        } else if (effect.kind === 'Render') {
+          renders.push({index: index++, place: effect.place});
+          functionEffects.push(effect);
+        }
+      }
+    }
+    const blockPhis = pendingPhis.get(block.id);
+    if (blockPhis != null) {
+      for (const {from, into, index} of blockPhis) {
+        state.assign(index, from, into);
+      }
+    }
+    if (block.terminal.kind === 'return') {
+      state.assign(index++, block.terminal.value, fn.returns);
+    }
+
+    if (
+      (block.terminal.kind === 'maybe-throw' ||
+        block.terminal.kind === 'return') &&
+      block.terminal.effects != null
+    ) {
+      for (const effect of block.terminal.effects) {
+        if (effect.kind === 'Alias') {
+          state.assign(index++, effect.from, effect.into);
+        } else {
+          CompilerError.invariant(effect.kind === 'Freeze', {
+            reason: `Unexpected '${effect.kind}' effect for MaybeThrow terminal`,
+            loc: block.terminal.loc,
+          });
+        }
+      }
+    }
+  }
+
+  for (const mutation of mutations) {
+    state.mutate(
+      mutation.index,
+      mutation.place.identifier,
+      makeInstructionId(mutation.id + 1),
+      mutation.transitive,
+      mutation.kind,
+      mutation.place.loc,
+      errors,
+    );
+  }
+  for (const render of renders) {
+    state.render(render.index, render.place.identifier, errors);
+  }
+  for (const param of [...fn.context, ...fn.params]) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    const node = state.nodes.get(place.identifier);
+    if (node == null) {
+      continue;
+    }
+    let mutated = false;
+    if (node.local != null) {
+      if (node.local.kind === MutationKind.Conditional) {
+        mutated = true;
+        functionEffects.push({
+          kind: 'MutateConditionally',
+          value: {...place, loc: node.local.loc},
+        });
+      } else if (node.local.kind === MutationKind.Definite) {
+        mutated = true;
+        functionEffects.push({
+          kind: 'Mutate',
+          value: {...place, loc: node.local.loc},
+        });
+      }
+    }
+    if (node.transitive != null) {
+      if (node.transitive.kind === MutationKind.Conditional) {
+        mutated = true;
+        functionEffects.push({
+          kind: 'MutateTransitiveConditionally',
+          value: {...place, loc: node.transitive.loc},
+        });
+      } else if (node.transitive.kind === MutationKind.Definite) {
+        mutated = true;
+        functionEffects.push({
+          kind: 'MutateTransitive',
+          value: {...place, loc: node.transitive.loc},
+        });
+      }
+    }
+    if (mutated) {
+      place.effect = Effect.Capture;
+    }
+  }
+
+  /**
+   * Part 2
+   * Add legacy operand-specific effects based on instruction effects and mutable ranges.
+   * Also fixes up operand mutable ranges, making sure that start is non-zero if the value
+   * is mutated (depended on by later passes like InferReactiveScopeVariables which uses this
+   * to filter spurious mutations of globals, which we now guard against more precisely)
+   */
+  for (const block of fn.body.blocks.values()) {
+    for (const phi of block.phis) {
+      // TODO: we don't actually set these effects today!
+      phi.place.effect = Effect.Store;
+      const isPhiMutatedAfterCreation: boolean =
+        phi.place.identifier.mutableRange.end >
+        (block.instructions.at(0)?.id ?? block.terminal.id);
+      for (const operand of phi.operands.values()) {
+        operand.effect = isPhiMutatedAfterCreation
+          ? Effect.Capture
+          : Effect.Read;
+      }
+      if (
+        isPhiMutatedAfterCreation &&
+        phi.place.identifier.mutableRange.start === 0
+      ) {
+        /*
+         * TODO: ideally we'd construct a precise start range, but what really
+         * matters is that the phi's range appears mutable (end > start + 1)
+         * so we just set the start to the previous instruction before this block
+         */
+        const firstInstructionIdOfBlock =
+          block.instructions.at(0)?.id ?? block.terminal.id;
+        phi.place.identifier.mutableRange.start = makeInstructionId(
+          firstInstructionIdOfBlock - 1,
+        );
+      }
+    }
+    for (const instr of block.instructions) {
+      for (const lvalue of eachInstructionLValue(instr)) {
+        lvalue.effect = Effect.ConditionallyMutate;
+        if (lvalue.identifier.mutableRange.start === 0) {
+          lvalue.identifier.mutableRange.start = instr.id;
+        }
+        if (lvalue.identifier.mutableRange.end === 0) {
+          lvalue.identifier.mutableRange.end = makeInstructionId(
+            Math.max(instr.id + 1, lvalue.identifier.mutableRange.end),
+          );
+        }
+      }
+      for (const operand of eachInstructionValueOperand(instr.value)) {
+        operand.effect = Effect.Read;
+      }
+      if (instr.effects == null) {
+        continue;
+      }
+      const operandEffects = new Map<IdentifierId, Effect>();
+      for (const effect of instr.effects) {
+        switch (effect.kind) {
+          case 'Assign':
+          case 'Alias':
+          case 'Capture':
+          case 'CreateFrom': {
+            const isMutatedOrReassigned =
+              effect.into.identifier.mutableRange.end > instr.id;
+            if (isMutatedOrReassigned) {
+              operandEffects.set(effect.from.identifier.id, Effect.Capture);
+              operandEffects.set(effect.into.identifier.id, Effect.Store);
+            } else {
+              operandEffects.set(effect.from.identifier.id, Effect.Read);
+              operandEffects.set(effect.into.identifier.id, Effect.Store);
+            }
+            break;
+          }
+          case 'CreateFunction':
+          case 'Create': {
+            break;
+          }
+          case 'Mutate': {
+            operandEffects.set(effect.value.identifier.id, Effect.Store);
+            break;
+          }
+          case 'Apply': {
+            CompilerError.invariant(false, {
+              reason: `[AnalyzeFunctions] Expected Apply effects to be replaced with more precise effects`,
+              loc: effect.function.loc,
+            });
+          }
+          case 'MutateTransitive':
+          case 'MutateConditionally':
+          case 'MutateTransitiveConditionally': {
+            operandEffects.set(
+              effect.value.identifier.id,
+              Effect.ConditionallyMutate,
+            );
+            break;
+          }
+          case 'Freeze': {
+            operandEffects.set(effect.value.identifier.id, Effect.Freeze);
+            break;
+          }
+          case 'ImmutableCapture': {
+            // no-op, Read is the default
+            break;
+          }
+          case 'Impure':
+          case 'Render':
+          case 'MutateFrozen':
+          case 'MutateGlobal': {
+            // no-op
+            break;
+          }
+          default: {
+            assertExhaustive(
+              effect,
+              `Unexpected effect kind ${(effect as any).kind}`,
+            );
+          }
+        }
+      }
+      for (const lvalue of eachInstructionLValue(instr)) {
+        const effect =
+          operandEffects.get(lvalue.identifier.id) ??
+          Effect.ConditionallyMutate;
+        lvalue.effect = effect;
+      }
+      for (const operand of eachInstructionValueOperand(instr.value)) {
+        if (
+          operand.identifier.mutableRange.end > instr.id &&
+          operand.identifier.mutableRange.start === 0
+        ) {
+          operand.identifier.mutableRange.start = instr.id;
+        }
+        const effect = operandEffects.get(operand.identifier.id) ?? Effect.Read;
+        operand.effect = effect;
+      }
+
+      /**
+       * This case is targeted at hoisted functions like:
+       *
+       * ```
+       * x();
+       * function x() { ... }
+       * ```
+       *
+       * Which turns into:
+       *
+       * t0 = DeclareContext HoistedFunction x
+       * t1 = LoadContext x
+       * t2 = CallExpression t1 ( )
+       * t3 = FunctionExpression ...
+       * t4 = StoreContext Function x = t3
+       *
+       * If the function had captured mutable values, it would already have its
+       * range extended to include the StoreContext. But if the function doesn't
+       * capture any mutable values its range won't have been extended yet. We
+       * want to ensure that the value is memoized along with the context variable,
+       * not independently of it (bc of the way we do codegen for hoisted functions).
+       * So here we check for StoreContext rvalues and if they haven't already had
+       * their range extended to at least this instruction, we extend it.
+       */
+      if (
+        instr.value.kind === 'StoreContext' &&
+        instr.value.value.identifier.mutableRange.end <= instr.id
+      ) {
+        instr.value.value.identifier.mutableRange.end = makeInstructionId(
+          instr.id + 1,
+        );
+      }
+    }
+    if (block.terminal.kind === 'return') {
+      block.terminal.value.effect = isFunctionExpression
+        ? Effect.Read
+        : Effect.Freeze;
+    } else {
+      for (const operand of eachTerminalOperand(block.terminal)) {
+        operand.effect = Effect.Read;
+      }
+    }
+  }
+
+  /**
+   * Part 3
+   * Finish populating the externally visible effects. Above we bubble-up the side effects
+   * (MutateFrozen/MutableGlobal/Impure/Render) as well as mutations of context variables.
+   * Here we populate an effect to create the return value as well as populating alias/capture
+   * effects for how data flows between the params, context vars, and return.
+   */
+  const returns = fn.returns.identifier;
+  functionEffects.push({
+    kind: 'Create',
+    into: fn.returns,
+    value: isPrimitiveType(returns)
+      ? ValueKind.Primitive
+      : isJsxType(returns.type)
+        ? ValueKind.Frozen
+        : ValueKind.Mutable,
+    reason: ValueReason.KnownReturnSignature,
+  });
+  /**
+   * Determine precise data-flow effects by simulating transitive mutations of the params/
+   * captures and seeing what other params/context variables are affected. Anything that
+   * would be transitively mutated needs a capture relationship.
+   */
+  const tracked: Array<Place> = [];
+  const ignoredErrors = new CompilerError();
+  for (const param of [...fn.params, ...fn.context, fn.returns]) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    tracked.push(place);
+  }
+  for (const into of tracked) {
+    const mutationIndex = index++;
+    state.mutate(
+      mutationIndex,
+      into.identifier,
+      null,
+      true,
+      MutationKind.Conditional,
+      into.loc,
+      ignoredErrors,
+    );
+    for (const from of tracked) {
+      if (
+        from.identifier.id === into.identifier.id ||
+        from.identifier.id === fn.returns.identifier.id
+      ) {
+        continue;
+      }
+      const fromNode = state.nodes.get(from.identifier);
+      CompilerError.invariant(fromNode != null, {
+        reason: `Expected a node to exist for all parameters and context variables`,
+        loc: into.loc,
+      });
+      if (fromNode.lastMutated === mutationIndex) {
+        if (into.identifier.id === fn.returns.identifier.id) {
+          // The return value could be any of the params/context variables
+          functionEffects.push({
+            kind: 'Alias',
+            from,
+            into,
+          });
+        } else {
+          // Otherwise params/context-vars can only capture each other
+          functionEffects.push({
+            kind: 'Capture',
+            from,
+            into,
+          });
+        }
+      }
+    }
+  }
+
+  if (errors.hasErrors() && !isFunctionExpression) {
+    return Err(errors);
+  }
+  return Ok(functionEffects);
+}
+
+function appendFunctionErrors(errors: CompilerError, fn: HIRFunction): void {
+  for (const effect of fn.aliasingEffects ?? []) {
+    switch (effect.kind) {
+      case 'Impure':
+      case 'MutateFrozen':
+      case 'MutateGlobal': {
+        errors.push(effect.error);
+        break;
+      }
+    }
+  }
+}
+
+export enum MutationKind {
+  None = 0,
+  Conditional = 1,
+  Definite = 2,
+}
+
+type Node = {
+  id: Identifier;
+  createdFrom: Map<Identifier, number>;
+  captures: Map<Identifier, number>;
+  aliases: Map<Identifier, number>;
+  edges: Array<{index: number; node: Identifier; kind: 'capture' | 'alias'}>;
+  transitive: {kind: MutationKind; loc: SourceLocation} | null;
+  local: {kind: MutationKind; loc: SourceLocation} | null;
+  lastMutated: number;
+  value:
+    | {kind: 'Object'}
+    | {kind: 'Phi'}
+    | {kind: 'Function'; function: HIRFunction};
+};
+class AliasingState {
+  nodes: Map<Identifier, Node> = new Map();
+
+  create(place: Place, value: Node['value']): void {
+    this.nodes.set(place.identifier, {
+      id: place.identifier,
+      createdFrom: new Map(),
+      captures: new Map(),
+      aliases: new Map(),
+      edges: [],
+      transitive: null,
+      local: null,
+      lastMutated: 0,
+      value,
+    });
+  }
+
+  createFrom(index: number, from: Place, into: Place): void {
+    this.create(into, {kind: 'Object'});
+    const fromNode = this.nodes.get(from.identifier);
+    const toNode = this.nodes.get(into.identifier);
+    if (fromNode == null || toNode == null) {
+      return;
+    }
+    fromNode.edges.push({index, node: into.identifier, kind: 'alias'});
+    if (!toNode.createdFrom.has(from.identifier)) {
+      toNode.createdFrom.set(from.identifier, index);
+    }
+  }
+
+  capture(index: number, from: Place, into: Place): void {
+    const fromNode = this.nodes.get(from.identifier);
+    const toNode = this.nodes.get(into.identifier);
+    if (fromNode == null || toNode == null) {
+      return;
+    }
+    fromNode.edges.push({index, node: into.identifier, kind: 'capture'});
+    if (!toNode.captures.has(from.identifier)) {
+      toNode.captures.set(from.identifier, index);
+    }
+  }
+
+  assign(index: number, from: Place, into: Place): void {
+    const fromNode = this.nodes.get(from.identifier);
+    const toNode = this.nodes.get(into.identifier);
+    if (fromNode == null || toNode == null) {
+      return;
+    }
+    fromNode.edges.push({index, node: into.identifier, kind: 'alias'});
+    if (!toNode.aliases.has(from.identifier)) {
+      toNode.aliases.set(from.identifier, index);
+    }
+  }
+
+  render(index: number, start: Identifier, errors: CompilerError): void {
+    const seen = new Set<Identifier>();
+    const queue: Array<Identifier> = [start];
+    while (queue.length !== 0) {
+      const current = queue.pop()!;
+      if (seen.has(current)) {
+        continue;
+      }
+      seen.add(current);
+      const node = this.nodes.get(current);
+      if (node == null || node.transitive != null || node.local != null) {
+        continue;
+      }
+      if (node.value.kind === 'Function') {
+        appendFunctionErrors(errors, node.value.function);
+      }
+      for (const [alias, when] of node.createdFrom) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(alias);
+      }
+      for (const [alias, when] of node.aliases) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(alias);
+      }
+      for (const [capture, when] of node.captures) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(capture);
+      }
+    }
+  }
+
+  mutate(
+    index: number,
+    start: Identifier,
+    // Null is used for simulated mutations
+    end: InstructionId | null,
+    transitive: boolean,
+    kind: MutationKind,
+    loc: SourceLocation,
+    errors: CompilerError,
+  ): void {
+    const seen = new Set<Identifier>();
+    const queue: Array<{
+      place: Identifier;
+      transitive: boolean;
+      direction: 'backwards' | 'forwards';
+    }> = [{place: start, transitive, direction: 'backwards'}];
+    while (queue.length !== 0) {
+      const {place: current, transitive, direction} = queue.pop()!;
+      if (seen.has(current)) {
+        continue;
+      }
+      seen.add(current);
+      const node = this.nodes.get(current);
+      if (node == null) {
+        continue;
+      }
+      node.lastMutated = Math.max(node.lastMutated, index);
+      if (end != null) {
+        node.id.mutableRange.end = makeInstructionId(
+          Math.max(node.id.mutableRange.end, end),
+        );
+      }
+      if (
+        node.value.kind === 'Function' &&
+        node.transitive == null &&
+        node.local == null
+      ) {
+        appendFunctionErrors(errors, node.value.function);
+      }
+      if (transitive) {
+        if (node.transitive == null || node.transitive.kind < kind) {
+          node.transitive = {kind, loc};
+        }
+      } else {
+        if (node.local == null || node.local.kind < kind) {
+          node.local = {kind, loc};
+        }
+      }
+      /**
+       * all mutations affect "forward" edges by the rules:
+       * - Capture a -> b, mutate(a) => mutate(b)
+       * - Alias a -> b, mutate(a) => mutate(b)
+       */
+      for (const edge of node.edges) {
+        if (edge.index >= index) {
+          break;
+        }
+        queue.push({place: edge.node, transitive, direction: 'forwards'});
+      }
+      for (const [alias, when] of node.createdFrom) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push({place: alias, transitive: true, direction: 'backwards'});
+      }
+      if (direction === 'backwards' || node.value.kind !== 'Phi') {
+        /**
+         * all mutations affect backward alias edges by the rules:
+         * - Alias a -> b, mutate(b) => mutate(a)
+         * - Alias a -> b, mutateTransitive(b) => mutate(a)
+         *
+         * However, if we reached a phi because one of its inputs was mutated
+         * (and we're advancing "forwards" through that node's edges), then
+         * we know we've already processed the mutation at its source. The
+         * phi's other inputs can't be affected.
+         */
+        for (const [alias, when] of node.aliases) {
+          if (when >= index) {
+            continue;
+          }
+          queue.push({place: alias, transitive, direction: 'backwards'});
+        }
+      }
+      /**
+       * but only transitive mutations affect captures
+       */
+      if (transitive) {
+        for (const [capture, when] of node.captures) {
+          if (when >= index) {
+            continue;
+          }
+          queue.push({place: capture, transitive, direction: 'backwards'});
+        }
+      }
+    }
+  }
+}

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

@@ -26,6 +26,7 @@ import {
 import {PostDominator} from '../HIR/Dominator';
 import {
   eachInstructionLValue,
+  eachInstructionOperand,
   eachInstructionValueOperand,
   eachTerminalOperand,
 } from '../HIR/visitors';
@@ -292,7 +293,7 @@ export function inferReactivePlaces(fn: HIRFunction): void {
         let hasReactiveInput = false;
         /*
          * NOTE: we want to mark all operands as reactive or not, so we
-         * avoid short-circuting here
+         * avoid short-circuiting here
          */
         for (const operand of eachInstructionValueOperand(value)) {
           const reactive = reactiveIdentifiers.isReactive(operand);
@@ -375,6 +376,41 @@ export function inferReactivePlaces(fn: HIRFunction): void {
       }
     }
   } while (reactiveIdentifiers.snapshot());
+
+  function propagateReactivityToInnerFunctions(
+    fn: HIRFunction,
+    isOutermost: boolean,
+  ): void {
+    for (const [, block] of fn.body.blocks) {
+      for (const instr of block.instructions) {
+        if (!isOutermost) {
+          for (const operand of eachInstructionOperand(instr)) {
+            reactiveIdentifiers.isReactive(operand);
+          }
+        }
+        if (
+          instr.value.kind === 'ObjectMethod' ||
+          instr.value.kind === 'FunctionExpression'
+        ) {
+          propagateReactivityToInnerFunctions(
+            instr.value.loweredFunc.func,
+            false,
+          );
+        }
+      }
+      if (!isOutermost) {
+        for (const operand of eachTerminalOperand(block.terminal)) {
+          reactiveIdentifiers.isReactive(operand);
+        }
+      }
+    }
+  }
+
+  /**
+   * Propagate reactivity for inner functions, as we eventually hoist and dedupe
+   * dependency instructions for scopes.
+   */
+  propagateReactivityToInnerFunctions(fn, true);
 }
 
 /*

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

@@ -48,7 +48,7 @@ import {
   eachTerminalOperand,
   eachTerminalSuccessor,
 } from '../HIR/visitors';
-import {assertExhaustive} from '../Utils/utils';
+import {assertExhaustive, Set_isSuperset} from '../Utils/utils';
 import {
   inferTerminalFunctionEffects,
   inferInstructionFunctionEffects,
@@ -779,7 +779,7 @@ function inferParam(
  * │         Mutable          │───┘
  * └──────────────────────────┘
  */
-function mergeValues(a: ValueKind, b: ValueKind): ValueKind {
+export function mergeValueKinds(a: ValueKind, b: ValueKind): ValueKind {
   if (a === b) {
     return a;
   } else if (a === ValueKind.MaybeFrozen || b === ValueKind.MaybeFrozen) {
@@ -821,28 +821,16 @@ function mergeValues(a: ValueKind, b: ValueKind): ValueKind {
   }
 }
 
-/**
- * @returns `true` if `a` is a superset of `b`.
- */
-function isSuperset<T>(a: ReadonlySet<T>, b: ReadonlySet<T>): boolean {
-  for (const v of b) {
-    if (!a.has(v)) {
-      return false;
-    }
-  }
-  return true;
-}
-
 function mergeAbstractValues(
   a: AbstractValue,
   b: AbstractValue,
 ): AbstractValue {
-  const kind = mergeValues(a.kind, b.kind);
+  const kind = mergeValueKinds(a.kind, b.kind);
   if (
     kind === a.kind &&
     kind === b.kind &&
-    isSuperset(a.reason, b.reason) &&
-    isSuperset(a.context, b.context)
+    Set_isSuperset(a.reason, b.reason) &&
+    Set_isSuperset(a.context, b.context)
   ) {
     return a;
   }
@@ -1989,7 +1977,7 @@ function areArgumentsImmutableAndNonMutating(
   return true;
 }
 
-function getArgumentEffect(
+export function getArgumentEffect(
   signatureEffect: Effect | null,
   arg: Place | SpreadPattern,
 ): Effect {

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

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

compiler/packages/babel-plugin-react-compiler/src/Inference/MUTABILITY_ALIASING_MODEL.md

@@ -0,0 +1,544 @@
+# The Mutability & Aliasing Model
+
+This document describes the new (as of June 2025) mutability and aliasing model powering React Compiler. The mutability and aliasing system is a conceptual subcomponent whose primary role is to determine minimal sets of values that mutate together, and the range of instructions over which those mutations occur. These minimal sets of values that mutate together, and the corresponding instructions doing those mutations, are ultimately grouped into reactive scopes, which then translate into memoization blocks in the output (after substantial additional processing described in the comments of those passes).
+
+To build an intuition, consider the following example:
+
+```js
+function Component() {
+    // a is created and mutated over the course of these two instructions:
+    const a = {};
+    mutate(a);
+
+    // b and c are created and mutated together — mutate might modify b via c
+    const b = {};
+    const c = {b};
+    mutate(c);
+
+    // does not modify a/b/c
+    return <Foo a={a} c={c} />
+}
+```
+
+The goal of mutability and aliasing inference is to understand the set of instructions that create/modify a, b, and c.
+
+In code, the mutability and aliasing model is compromised of the following phases:
+
+* `InferMutationAliasingEffects`. Infers a set of mutation and aliasing effects for each instruction. The approach is to generate a set of candidate effects based purely on the semantics of each instruction and the types of the operands, then use abstract interpretation to determine the actual effects (or errros) that would apply. For example, an instruction that by default has a Capture effect might downgrade to an ImmutableCapture effect if the value is known to be frozen.
+* `InferMutationAliasingRanges`. Infers a mutable range (start:end instruction ids) for each value in the program, and annotates each Place with its effect type for usage in later passes. This builds a graph of data flow through the program over time in order to understand which mutations effect which values.
+* `InferReactiveScopeVariables`. Given the per-Place effects, determines disjoint sets of values that mutate together and assigns all identifiers in each set to a unique scope, and updates the range to include the ranges of all constituent values.
+
+Finally, `AnalyzeFunctions` needs to understand the mutation and aliasing semantics of nested FunctionExpression and ObjectMethod values. `AnalyzeFunctions` calls `InferFunctionExpressionAliasingEffectsSignature` to determine the publicly observable set of mutation/aliasing effects for nested functions.
+
+## Mutation and Aliasing Effects
+
+The inference model is based on a set of "effects" that describe subtle aspects of mutation, aliasing, and other changes to the state of values over time
+
+### Creation Effects
+
+#### Create
+
+```js
+{
+    kind: 'Create';
+    into: Place;
+    value: ValueKind;
+    reason: ValueReason;
+}
+```
+
+Describes the creation of a new value with the given kind, and reason for having that kind. For example, `x = 10` might have an effect like `Create x = ValueKind.Primitive [ValueReason.Other]`.
+
+#### CreateFunction
+
+```js
+{
+    kind: 'CreateFunction';
+    captures: Array<Place>;
+    function: FunctionExpression | ObjectMethod;
+    into: Place;
+}
+```
+
+Describes the creation of new function value, capturing the given set of mutable values. CreateFunction is used to specifically track function types so that we can precisely model calls to those functions with `Apply`.
+
+#### Apply
+
+```js
+{
+    kind: 'Apply';
+    receiver: Place;
+    function: Place; // same as receiver for function calls
+    mutatesFunction: boolean; // indicates if this is a type that we consdier to mutate the function itself by default
+    args: Array<Place | SpreadPattern | Hole>;
+    into: Place; // where result is stored
+    signature: FunctionSignature | null;
+}
+```
+
+Describes the potential creation of a value by calling a function. This models `new`, function calls, and method calls. The inference algorithm uses the most precise signature it can determine:
+
+* If the function is a locally created function expression, we use a signature inferred from the behavior of that function to interpret the effects of calling it with the given arguments.
+* Else if the function has a known aliasing signature (new style precise effects signature), we apply the arguments to that signature to get a precise set of effects.
+* Else if the function has a legacy style signature (with per-param effects) we convert the legacy per-Place effects into aliasing effects (described in this doc) and apply those.
+* Else fall back to inferring a generic set of effects.
+
+The generic fallback is to assume:
+- The return value may alias any of the arguments (Alias param -> return)
+- Any arguments *may* be transitively mutated (MutateTransitiveConditionally param)
+- Any argument may be captured into any other argument (Capture paramN -> paramM for all N,M where N != M)
+
+### Aliasing Effects
+
+These effects describe data-flow only, separately from mutation or other state-changing semantics.
+
+#### Assign
+
+```js
+{
+    kind: 'Assign';
+    from: Place;
+    into: Place;
+}
+```
+
+Describes an `x = y` assignment, where the receiving (into) value is overwritten with a new (from) value. After this effect, any previous assignments/aliases to the receiving value are dropped. Note that `Alias` initializes the receiving value.
+
+> TODO: InferMutationAliasingRanges may not fully reset aliases on encountering this effect
+
+#### Alias
+
+```js
+{
+    kind: 'Alias';
+    from: Place;
+    into: Place;
+}
+```
+
+Describes that an assignment _may_ occur, but that the possible assignment is non-exclusive. The canonical use-case for `Alias` is a function that may return more than one of its arguments, such as `(x, y, z) => x ? y : z`. Here, the result of this function may be `y` or `z`, but neither one overwrites the other. Note that `Alias` does _not_ initialize the receiving value: it should always be paired with an effect to create the receiving value.
+
+#### Capture
+
+```js
+{
+    kind: 'Capture';
+    from: Place;
+    into: Place;
+}
+```
+
+Describes that a reference to one variable (from) is stored within another value (into). Examples include:
+- An array expression captures the items of the array (`array = [capturedValue]`)
+- Array.prototype.push captures the pushed values into the array (`array.push(capturedValue)`)
+- Property assignment captures the value onto the object (`object.property = capturedValue`)
+
+#### CreateFrom
+
+```js
+{
+    kind: 'CreateFrom';
+    from: Place;
+    into: Place;
+}
+```
+
+This is somewhat the inverse of `Capture`. The `CreateFrom` effect describes that a variable is initialized by extracting _part_ of another value, without taking a direct alias to the full other value. Examples include:
+
+- Indexing into an array (`createdFrom = array[0]`)
+- Reading an object property (`createdFrom = object.property`)
+- Getting a Map key (`createdFrom = map.get(key)`)
+
+#### ImmutableCapture
+
+Describes immutable data flow from one value to another. This is not currently used for anything, but is intended to eventually power a more sophisticated escape analysis.
+
+### State-Changing Effects
+
+The following effects describe state changes to specific values, not data flow. In many cases, JavaScript semantics will involve a combination of both data-flow effects *and* state-change effects. For example, `object.property = value` has data flow (`Capture object <- value`) and mutation (`Mutate object`).
+
+#### Freeze
+
+```js
+{
+    kind: 'Freeze',
+    // The reference being frozen
+    value: Place;
+    // The reason the value is frozen (passed to a hook, passed to jsx, etc)
+    reason: ValueReason;
+}
+```
+
+Once a reference to a value has been passed to React, that value is generally not safe to mutate further. This is not a strictly required property of React, but is a natural consequence of making components and hooks composable without leaking implementation details. Concretely, once a value has been passed as a JSX prop, passed as argument to a hook, or returned from a hook, it must be assumed that the other "side" — receiver of the prop/argument/return value — will use that value as an input to an effect or memoization unit. Mutating that value (instead of creating a new value) will fail to cause the consuming computation to update:
+
+```js
+// INVALID DO NOT DO THIS
+function Component(props) {
+    const array = useArray(props.value);
+    // OOPS! this value is memoized, the array won't get re-created
+    // when `props.value` changes, so we might just keep pushing new
+    // values to the same array on every render!
+    array.push(props.otherValue);
+}
+
+function useArray(a) {
+    return useMemo(() => [a], [a]);
+}
+```
+
+The **Freeze** effect accepts a variable reference and a reason that the value is being frozen. Note: _freeze only applies to the reference, not the underlying value_. Our inference is conservative, and assumes that there may still be other references to the same underlying value which are mutated later. For example:
+
+```js
+const x = {};
+const y = [];
+x.y = y;
+freeze(y); // y _reference_ is frozen
+x.y.push(props.value); // but y is still considered mutable bc of this
+```
+
+#### Mutate (and MutateConditionally)
+
+```js
+{
+    kind: 'Mutate';
+    value: Place;
+}
+```
+
+Mutate indicates that a value is mutated, without modifying any of the values that it may transitively have captured. Canonical examples include:
+
+- Pushing an item onto an array modifies the array, but does not modify any items stored _within_ the array (unless the array has a reference to itself!)
+- Assigning a value to an object property modifies the object, but not any values stored in the object's other properties.
+
+This helps explain the distinction between Assign/Alias and Capture: Mutate only affects assign/alias but not captures.
+
+`MutateConditionally` is an alternative in which the mutation _may_ happen depending on the type of the value. The conditional variant is not generally used and included for completeness.
+
+
+
+#### MutateTransitiveConditionally (and MutateTransitive)
+
+`MutateTransitiveConditionally` represents an operation that may mutate _any_ aspect of a value, including reaching arbitrarily deep into nested values to mutate them. This is the default semantic for unknown functions — we have no idea what they do, so we assume that they are idempotent but may mutate any aspect of the mutable values that are passed to them.
+
+There is also `MutateTransitive` for completeness, but this is not generally used.
+
+### Side Effects
+
+Finally, there are a few effects that describe error, or potential error, conditions:
+
+- `MutateFrozen` is always an error, because it indicates known mutation of a value that should not be mutated.
+- `MutateGlobal` indicates known mutation of a global value, which is not safe during render. This effect is an error if reachable during render, but allowed if only reachable via an event handler or useEffect.
+- `Impure` indicates calling some other logic that is impure/side-effecting. This is an error if reachable during render, but allowed if only reachable via an event handler or useEffect.
+  - TODO: we could probably merge this and MutateGlobal
+- `Render` indicates a value that is not mutated, but is known to be called during render. It's used for a few particular places like JSX tags and JSX children, which we assume are accessed during render (while other props may be event handlers etc). This helps to detect more MutateGlobal/Impure effects and reject more invalid programs.
+
+
+## Rules
+
+### Mutation of Alias Mutates the Source Value
+
+```
+Alias a <- b
+Mutate a
+=>
+Mutate b
+```
+
+Example:
+
+```js
+const a = maybeIdentity(b); // Alias a <- b
+a.property = value; // a could be b, so this mutates b
+```
+
+### Mutation of Assignment Mutates the Source Value
+
+```
+Assign a <- b
+Mutate a
+=>
+Mutate b
+```
+
+Example:
+
+```js
+const a = b;
+a.property = value // a _is_ b, this mutates b
+```
+
+### Mutation of CreateFrom Mutates the Source Value
+
+```
+CreateFrom a <- b
+Mutate a
+=>
+Mutate b
+```
+
+Example:
+
+```js
+const a = b[index];
+a.property = value // the contents of b are transitively mutated
+```
+
+
+### Mutation of Capture Does *Not* Mutate the Source Value
+
+```
+Capture a <- b
+Mutate a
+!=>
+~Mutate b~
+```
+
+Example:
+
+```js
+const a = {};
+a.b = b;
+a.property = value; // mutates a, not b
+```
+
+### Mutation of Source Affects Alias, Assignment, CreateFrom, and Capture
+
+```
+Alias a <- b OR Assign a <- b OR CreateFrom a <- b OR Capture a <- b
+Mutate b
+=>
+Mutate a
+```
+
+A derived value changes when it's source value is mutated.
+
+Example:
+
+```js
+const x = {};
+const y = [x];
+x.y = true; // this changes the value within `y` ie mutates y
+```
+
+
+### TransitiveMutation of Alias, Assignment, CreateFrom, or Capture Mutates the Source
+
+```
+Alias a <- b OR Assign a <- b OR CreateFrom a <- b OR Capture a <- b
+MutateTransitive a
+=>
+MutateTransitive b
+```
+
+Remember, the intuition for a transitive mutation is that it's something that could traverse arbitrarily deep into an object and mutate whatever it finds. Imagine something that recurses into every nested object/array and sets `.field = value`. Given a function `mutate()` that does this, then:
+
+```js
+const a = b; // assign
+mutate(a); // clearly can transitively mutate b
+
+const a = maybeIdentity(b); // alias
+mutate(a); // clearly can transitively mutate b
+
+const a = b[index]; // createfrom
+mutate(a); // clearly can transitively mutate b
+
+const a = {};
+a.b = b; // capture
+mutate(a); // can transitively mutate b
+```
+
+### Freeze Does Not Freeze the Value
+
+Freeze does not freeze the value itself:
+
+```
+Create x
+Assign y <- x OR Alias y <- x OR CreateFrom y <- x OR Capture y <- x
+Freeze y
+!=>
+~Freeze x~
+```
+
+This means that subsequent mutations of the original value are valid:
+
+```
+Create x
+Assign y <- x OR Alias y <- x OR CreateFrom y <- x OR Capture y <- x
+Freeze y
+Mutate x
+=>
+Mutate x (mutation is ok)
+```
+
+As well as mutations through other assignments/aliases/captures/createfroms of the original value:
+
+```
+Create x
+Assign y <- x OR Alias y <- x OR CreateFrom y <- x OR Capture y <- x
+Freeze y
+Alias z <- x OR Capture z <- x OR CreateFrom z <- x OR Assign z <- x
+Mutate z
+=>
+Mutate x (mutation is ok)
+```
+
+### Freeze Freezes The Reference 
+
+Although freeze doesn't freeze the value, it does affect the reference. The reference cannot be used to mutate.
+
+Conditional mutations of the reference are no-ops:
+
+```
+Create x
+Assign y <- x OR Alias y <- x OR CreateFrom y <- x OR Capture y <- x
+Freeze y
+MutateConditional y
+=>
+(no mutation)
+```
+
+And known mutations of the reference are errors:
+
+```
+Create x
+Assign y <- x OR Alias y <- x OR CreateFrom y <- x OR Capture y <- x
+Freeze y
+MutateConditional y
+=>
+MutateFrozen y error=...
+```
+
+### Corollary: Transitivity of Assign/Alias/CreateFrom/Capture
+
+A key part of the inference model is inferring a signature for function expressions. The signature is a minimal set of effects that describes the publicly observable behavior of the function. This can include "global" effects like side effects (MutateGlobal/Impure) as well as mutations/aliasing of parameters and free variables.
+
+In order to determine the aliasing of params and free variables into each other and/or the return value, we may encounter chains of assign, alias, createfrom, and capture effects. For example:
+
+```js
+const f = (x) => {
+    const y = [x];  // capture y <- x
+    const z = y[0]; // createfrom z <- y
+    return z;     // assign return <- z
+}
+// <Effect> return <- x
+```
+
+In this example we can see that there should be some effect on `f` that tracks the flow of data from `x` into the return value. The key constraint is preserving the semantics around how local/transitive mutations of the destination would affect the source.
+
+#### Each of the effects is transitive with itself
+
+```
+Assign b <- a
+Assign c <- b
+=>
+Assign c <- a
+```
+
+```
+Alias b <- a
+Alias c <- b
+=>
+Alias c <- a
+```
+
+```
+CreateFrom b <- a
+CreateFrom c <- b
+=>
+CreateFrom c <- a
+```
+
+```
+Capture b <- a
+Capture c <- b
+=>
+Capture c <- a
+```
+
+#### Alias > Assign
+
+```
+Assign b <- a
+Alias c <- b
+=>
+Alias c <- a
+```
+
+```
+Alias b <- a
+Assign c <- b
+=>
+Alias c <- a
+```
+
+### CreateFrom > Assign/Alias
+
+Intuition: 
+
+```
+CreateFrom b <- a
+Alias c <- b OR Assign c <- b
+=>
+CreateFrom c <- a
+```
+
+```
+Alias b <- a OR Assign b <- a
+CreateFrom c <- b
+=>
+CreateFrom c <- a
+```
+
+### Capture > Assign/Alias
+
+Intuition: capturing means that a local mutation of the destination will not affect the source, so we preserve the capture.
+
+```
+Capture b <- a
+Alias c <- b OR Assign c <- b
+=>
+Capture c <- a
+```
+
+```
+Alias b <- a OR Assign b <- a
+Capture c <- b
+=>
+Capture c <- a
+```
+
+### Capture And CreateFrom
+
+Intuition: these effects are inverses of each other (capturing into an object, extracting from an object). The result is based on the order of operations:
+
+Capture then CreatFrom is equivalent to Alias: we have to assume that the result _is_ the original value and that a local mutation of the result could mutate the original.
+
+```js
+const b = [a]; // capture
+const c = b[0]; // createfrom
+mutate(c); // this clearly can mutate a, so the result must be one of Assign/Alias/CreateFrom 
+```
+
+We use Alias as the return type because the mutability kind of the result is not derived from the source value (there's a fresh object in between due to the capture), so the full set of effects in practice would be a Create+Alias.
+
+```
+Capture b <- a
+CreateFrom c <- b
+=>
+Alias c <- a
+```
+
+Meanwhile the opposite direction preserves the capture, because the result is not the same as the source:
+
+```js
+const b = a[0]; // createfrom
+const c = [b]; // capture
+mutate(c); // does not mutate a, so the result must be Capture
+```
+
+```
+CreateFrom b <- a
+Capture c <- b
+=>
+Capture c <- a
+```

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

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

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

@@ -25,7 +25,6 @@ import {
   makeBlockId,
   makeInstructionId,
   makePropertyLiteral,
-  makeType,
   markInstructionIds,
   promoteTemporary,
   reversePostorderBlocks,
@@ -146,6 +145,7 @@ function emitLoadLoweredContextCallee(
     id: makeInstructionId(0),
     loc: GeneratedSource,
     lvalue: createTemporaryPlace(env, GeneratedSource),
+    effects: null,
     value: loadGlobal,
   };
 }
@@ -192,6 +192,7 @@ function emitPropertyLoad(
     lvalue: object,
     value: loadObj,
     id: makeInstructionId(0),
+    effects: null,
     loc: GeneratedSource,
   };
 
@@ -206,6 +207,7 @@ function emitPropertyLoad(
     lvalue: element,
     value: loadProp,
     id: makeInstructionId(0),
+    effects: null,
     loc: GeneratedSource,
   };
   return {
@@ -237,6 +239,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
       kind: 'return',
       loc: GeneratedSource,
       value: arrayInstr.lvalue,
+      effects: null,
     },
     preds: new Set(),
     phis: new Set(),
@@ -249,7 +252,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
     env,
     params: [obj],
     returnTypeAnnotation: null,
-    returnType: makeType(),
+    returns: createTemporaryPlace(env, GeneratedSource),
     context: [],
     effects: null,
     body: {
@@ -278,6 +281,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
       loc: GeneratedSource,
     },
     lvalue: createTemporaryPlace(env, GeneratedSource),
+    effects: null,
     loc: GeneratedSource,
   };
   return fnInstr;
@@ -294,6 +298,7 @@ function emitArrayInstr(elements: Array<Place>, env: Environment): Instruction {
     id: makeInstructionId(0),
     value: array,
     lvalue: arrayLvalue,
+    effects: null,
     loc: GeneratedSource,
   };
   return arrayInstr;

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

@@ -21,7 +21,6 @@ import {
   makeBlockId,
   makeIdentifierName,
   makeInstructionId,
-  makeType,
   ObjectProperty,
   Place,
   promoteTemporary,
@@ -297,6 +296,7 @@ function emitOutlinedJsx(
       },
       loc: GeneratedSource,
     },
+    effects: null,
   };
   promoteTemporaryJsxTag(loadJsx.lvalue.identifier);
   const jsxExpr: Instruction = {
@@ -312,6 +312,7 @@ function emitOutlinedJsx(
       openingLoc: GeneratedSource,
       closingLoc: GeneratedSource,
     },
+    effects: null,
   };
 
   return [loadJsx, jsxExpr];
@@ -353,6 +354,7 @@ function emitOutlinedFn(
       kind: 'return',
       loc: GeneratedSource,
       value: instructions.at(-1)!.lvalue,
+      effects: null,
     },
     preds: new Set(),
     phis: new Set(),
@@ -365,7 +367,7 @@ function emitOutlinedFn(
     env,
     params: [propsObj],
     returnTypeAnnotation: null,
-    returnType: makeType(),
+    returns: createTemporaryPlace(env, GeneratedSource),
     context: [],
     effects: null,
     body: {
@@ -517,6 +519,7 @@ function emitDestructureProps(
       loc: GeneratedSource,
       value: propsObj,
     },
+    effects: null,
   };
   return destructurePropsInstr;
 }

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

@@ -44,7 +44,7 @@ import {
   getHookKind,
   makeIdentifierName,
 } from '../HIR/HIR';
-import {printIdentifier, printPlace} from '../HIR/PrintHIR';
+import {printIdentifier, printInstruction, printPlace} from '../HIR/PrintHIR';
 import {eachPatternOperand} from '../HIR/visitors';
 import {Err, Ok, Result} from '../Utils/Result';
 import {GuardKind} from '../Utils/RuntimeDiagnosticConstants';
@@ -349,11 +349,9 @@ function codegenReactiveFunction(
   fn: ReactiveFunction,
 ): Result<CodegenFunction, CompilerError> {
   for (const param of fn.params) {
-    if (param.kind === 'Identifier') {
-      cx.temp.set(param.identifier.declarationId, null);
-    } else {
-      cx.temp.set(param.place.identifier.declarationId, null);
-    }
+    const place = param.kind === 'Identifier' ? param : param.place;
+    cx.temp.set(place.identifier.declarationId, null);
+    cx.declare(place.identifier);
   }
 
   const params = fn.params.map(param => convertParameter(param));
@@ -1183,7 +1181,7 @@ function codegenTerminal(
               ? codegenPlaceToExpression(cx, case_.test)
               : null;
           const block = codegenBlock(cx, case_.block!);
-          return t.switchCase(test, [block]);
+          return t.switchCase(test, block.body.length === 0 ? [] : [block]);
         }),
       );
     }
@@ -1310,7 +1308,7 @@ function codegenInstructionNullable(
         });
         CompilerError.invariant(value?.type === 'FunctionExpression', {
           reason: 'Expected a function as a function declaration value',
-          description: null,
+          description: `Got ${value == null ? String(value) : value.type} at ${printInstruction(instr)}`,
           loc: instr.value.loc,
           suggestions: null,
         });
@@ -1726,7 +1724,7 @@ function codegenInstructionValue(
     }
     case 'UnaryExpression': {
       value = t.unaryExpression(
-        instrValue.operator as 'throw', // todo
+        instrValue.operator,
         codegenPlaceToExpression(cx, instrValue.value),
       );
       break;
@@ -2582,7 +2580,16 @@ function codegenValue(
   value: boolean | number | string | null | undefined,
 ): t.Expression {
   if (typeof value === 'number') {
-    return t.numericLiteral(value);
+    if (value < 0) {
+      /**
+       * Babel's code generator produces invalid JS for negative numbers when
+       * run with { compact: true }.
+       * See repro https://codesandbox.io/p/devbox/5d47fr
+       */
+      return t.unaryExpression('-', t.numericLiteral(-value), false);
+    } else {
+      return t.numericLiteral(value);
+    }
   } else if (typeof value === 'boolean') {
     return t.booleanLiteral(value);
   } else if (typeof value === 'string') {

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

@@ -79,6 +79,10 @@ export function extractScopeDeclarationsFromDestructuring(
   fn: ReactiveFunction,
 ): void {
   const state = new State(fn.env);
+  for (const param of fn.params) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    state.declared.add(place.identifier.declarationId);
+  }
   visitReactiveFunction(fn, new Visitor(), state);
 }
 

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

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

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

@@ -436,6 +436,7 @@ function makeLoadUseFireInstruction(
     value: instrValue,
     lvalue: {...useFirePlace},
     loc: GeneratedSource,
+    effects: null,
   };
 }
 
@@ -460,6 +461,7 @@ function makeLoadFireCalleeInstruction(
     },
     lvalue: {...loadedFireCallee},
     loc: GeneratedSource,
+    effects: null,
   };
 }
 
@@ -483,6 +485,7 @@ function makeCallUseFireInstruction(
     value: useFireCall,
     lvalue: {...useFireCallResultPlace},
     loc: GeneratedSource,
+    effects: null,
   };
 }
 
@@ -511,6 +514,7 @@ function makeStoreUseFireInstruction(
     },
     lvalue: fireFunctionBindingLValuePlace,
     loc: GeneratedSource,
+    effects: null,
   };
 }
 

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

@@ -90,7 +90,8 @@ function apply(func: HIRFunction, unifier: Unifier): void {
       }
     }
   }
-  func.returnType = unifier.get(func.returnType);
+  const returns = func.returns.identifier;
+  returns.type = unifier.get(returns.type);
 }
 
 type TypeEquation = {
@@ -143,12 +144,12 @@ function* generate(
     }
   }
   if (returnTypes.length > 1) {
-    yield equation(func.returnType, {
+    yield equation(func.returns.identifier.type, {
       kind: 'Phi',
       operands: returnTypes,
     });
   } else if (returnTypes.length === 1) {
-    yield equation(func.returnType, returnTypes[0]!);
+    yield equation(func.returns.identifier.type, returnTypes[0]!);
   }
 }
 
@@ -407,7 +408,7 @@ function* generateInstructionTypes(
       yield equation(left, {
         kind: 'Function',
         shapeId: BuiltInFunctionId,
-        return: value.loweredFunc.func.returnType,
+        return: value.loweredFunc.func.returns.identifier.type,
         isConstructor: false,
       });
       break;

compiler/packages/babel-plugin-react-compiler/src/Utils/TestUtils.ts

@@ -93,6 +93,21 @@ const testComplexConfigDefaults: PartialEnvironmentConfig = {
     },
   ],
 };
+
+function* splitPragma(
+  pragma: string,
+): Generator<{key: string; value: string | null}> {
+  for (const entry of pragma.split('@')) {
+    const keyVal = entry.trim();
+    const valIdx = keyVal.indexOf(':');
+    if (valIdx === -1) {
+      yield {key: keyVal.split(' ', 1)[0], value: null};
+    } else {
+      yield {key: keyVal.slice(0, valIdx), value: keyVal.slice(valIdx + 1)};
+    }
+  }
+}
+
 /**
  * For snap test fixtures and playground only.
  */
@@ -101,19 +116,11 @@ function parseConfigPragmaEnvironmentForTest(
 ): EnvironmentConfig {
   const maybeConfig: Partial<Record<keyof EnvironmentConfig, unknown>> = {};
 
-  for (const token of pragma.split(' ')) {
-    if (!token.startsWith('@')) {
-      continue;
-    }
-    const keyVal = token.slice(1);
-    const valIdx = keyVal.indexOf(':');
-    const key = valIdx === -1 ? keyVal : keyVal.slice(0, valIdx);
-    const val = valIdx === -1 ? undefined : keyVal.slice(valIdx + 1);
-    const isSet = val === undefined || val === 'true';
+  for (const {key, value: val} of splitPragma(pragma)) {
     if (!hasOwnProperty(EnvironmentConfigSchema.shape, key)) {
       continue;
     }
-
+    const isSet = val == null || val === 'true';
     if (isSet && key in testComplexConfigDefaults) {
       maybeConfig[key] = testComplexConfigDefaults[key];
     } else if (isSet) {
@@ -176,18 +183,11 @@ export function parseConfigPragmaForTests(
     compilationMode: defaults.compilationMode,
     environment,
   };
-  for (const token of pragma.split(' ')) {
-    if (!token.startsWith('@')) {
-      continue;
-    }
-    const keyVal = token.slice(1);
-    const idx = keyVal.indexOf(':');
-    const key = idx === -1 ? keyVal : keyVal.slice(0, idx);
-    const val = idx === -1 ? undefined : keyVal.slice(idx + 1);
+  for (const {key, value: val} of splitPragma(pragma)) {
     if (!hasOwnProperty(defaultOptions, key)) {
       continue;
     }
-    const isSet = val === undefined || val === 'true';
+    const isSet = val == null || val === 'true';
     if (isSet && key in testComplexPluginOptionDefaults) {
       options[key] = testComplexPluginOptionDefaults[key];
     } else if (isSet) {

compiler/packages/babel-plugin-react-compiler/src/Utils/utils.ts

@@ -121,6 +121,21 @@ export function Set_intersect<T>(sets: Array<ReadonlySet<T>>): Set<T> {
   return result;
 }
 
+/**
+ * @returns `true` if `a` is a superset of `b`.
+ */
+export function Set_isSuperset<T>(
+  a: ReadonlySet<T>,
+  b: ReadonlySet<T>,
+): boolean {
+  for (const v of b) {
+    if (!a.has(v)) {
+      return false;
+    }
+  }
+  return true;
+}
+
 export function Iterable_some<T>(
   iter: Iterable<T>,
   pred: (item: T) => boolean,

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

@@ -58,8 +58,7 @@ export function validateNoFreezingKnownMutableFunctions(
       const effect = contextMutationEffects.get(operand.identifier.id);
       if (effect != null) {
         errors.push({
-          reason: `This argument is a function which modifies local variables when called, which can bypass memoization and cause the UI not to update`,
-          description: `Functions that are returned from hooks, passed as arguments to hooks, or passed as props to components may not mutate local variables`,
+          reason: `This argument is a function which may reassign or mutate local variables after render, which can cause inconsistent behavior on subsequent renders. Consider using state instead`,
           loc: operand.loc,
           severity: ErrorSeverity.InvalidReact,
         });
@@ -112,6 +111,55 @@ export function validateNoFreezingKnownMutableFunctions(
           );
           if (knownMutation && knownMutation.kind === 'ContextMutation') {
             contextMutationEffects.set(lvalue.identifier.id, knownMutation);
+          } else if (
+            fn.env.config.enableNewMutationAliasingModel &&
+            value.loweredFunc.func.aliasingEffects != null
+          ) {
+            const context = new Set(
+              value.loweredFunc.func.context.map(p => p.identifier.id),
+            );
+            effects: for (const effect of value.loweredFunc.func
+              .aliasingEffects) {
+              switch (effect.kind) {
+                case 'Mutate':
+                case 'MutateTransitive': {
+                  const knownMutation = contextMutationEffects.get(
+                    effect.value.identifier.id,
+                  );
+                  if (knownMutation != null) {
+                    contextMutationEffects.set(
+                      lvalue.identifier.id,
+                      knownMutation,
+                    );
+                  } else if (
+                    context.has(effect.value.identifier.id) &&
+                    !isRefOrRefLikeMutableType(effect.value.identifier.type)
+                  ) {
+                    contextMutationEffects.set(lvalue.identifier.id, {
+                      kind: 'ContextMutation',
+                      effect: Effect.Mutate,
+                      loc: effect.value.loc,
+                      places: new Set([effect.value]),
+                    });
+                    break effects;
+                  }
+                  break;
+                }
+                case 'MutateConditionally':
+                case 'MutateTransitiveConditionally': {
+                  const knownMutation = contextMutationEffects.get(
+                    effect.value.identifier.id,
+                  );
+                  if (knownMutation != null) {
+                    contextMutationEffects.set(
+                      lvalue.identifier.id,
+                      knownMutation,
+                    );
+                  }
+                  break;
+                }
+              }
+            }
           }
           break;
         }

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

@@ -9,7 +9,7 @@ export {validateContextVariableLValues} from './ValidateContextVariableLValues';
 export {validateHooksUsage} from './ValidateHooksUsage';
 export {validateMemoizedEffectDependencies} from './ValidateMemoizedEffectDependencies';
 export {validateNoCapitalizedCalls} from './ValidateNoCapitalizedCalls';
-export {validateNoRefAccessInRender} from './ValidateNoRefAccesInRender';
+export {validateNoRefAccessInRender} from './ValidateNoRefAccessInRender';
 export {validateNoSetStateInRender} from './ValidateNoSetStateInRender';
 export {validatePreservedManualMemoization} from './ValidatePreservedManualMemoization';
 export {validateUseMemo} from './ValidateUseMemo';

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/aliased-nested-scope-truncated-dep.expect.md

@@ -175,21 +175,14 @@ import {
  * and mutability.
  */
 function Component(t0) {
-  const $ = _c(4);
+  const $ = _c(2);
   const { prop } = t0;
   let t1;
   if ($[0] !== prop) {
     const obj = shallowCopy(prop);
     const aliasedObj = identity(obj);
-    let t2;
-    if ($[2] !== obj) {
-      t2 = [obj.id];
-      $[2] = obj;
-      $[3] = t2;
-    } else {
-      t2 = $[3];
-    }
-    const id = t2;
+
+    const id = [obj.id];
 
     mutate(aliasedObj);
     setPropertyByKey(aliasedObj, "id", prop.id + 1);

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/babel-repro-compact-negative-number.expect.md

@@ -0,0 +1,56 @@
+
+## Input
+
+```javascript
+import {Stringify} from 'shared-runtime';
+
+function Repro(props) {
+  const MY_CONST = -2;
+  return <Stringify>{props.arg - MY_CONST}</Stringify>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Repro,
+  params: [
+    {
+      arg: 3,
+    },
+  ],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { Stringify } from "shared-runtime";
+
+function Repro(props) {
+  const $ = _c(2);
+
+  const t0 = props.arg - -2;
+  let t1;
+  if ($[0] !== t0) {
+    t1 = <Stringify>{t0}</Stringify>;
+    $[0] = t0;
+    $[1] = t1;
+  } else {
+    t1 = $[1];
+  }
+  return t1;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Repro,
+  params: [
+    {
+      arg: 3,
+    },
+  ],
+};
+
+```
+      
+### Eval output
+(kind: ok) <div>{"children":5}</div>

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/babel-repro-compact-negative-number.js

@@ -0,0 +1,15 @@
+import {Stringify} from 'shared-runtime';
+
+function Repro(props) {
+  const MY_CONST = -2;
+  return <Stringify>{props.arg - MY_CONST}</Stringify>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Repro,
+  params: [
+    {
+      arg: 3,
+    },
+  ],
+};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/block-scoping-switch-variable-scoping.expect.md

@@ -50,8 +50,7 @@ function Component(props) {
       console.log(handlers.value);
       break bb0;
     }
-    default: {
-    }
+    default:
   }
 
   t0 = handlers;

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-aliased-capture-aliased-mutate.expect.md

@@ -2,7 +2,7 @@
 ## Input
 
 ```javascript
-// @flow @enableTransitivelyFreezeFunctionExpressions:false
+// @flow @enableTransitivelyFreezeFunctionExpressions:false @enableNewMutationAliasingModel:false
 import {arrayPush, setPropertyByKey, Stringify} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-aliased-capture-aliased-mutate.js

@@ -1,4 +1,4 @@
-// @flow @enableTransitivelyFreezeFunctionExpressions:false
+// @flow @enableTransitivelyFreezeFunctionExpressions:false @enableNewMutationAliasingModel:false
 import {arrayPush, setPropertyByKey, Stringify} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-aliased-capture-mutate.expect.md

@@ -2,7 +2,7 @@
 ## Input
 
 ```javascript
-// @flow @enableTransitivelyFreezeFunctionExpressions:false
+// @flow @enableTransitivelyFreezeFunctionExpressions:false @enableNewMutationAliasingModel:false
 import {setPropertyByKey, Stringify} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-aliased-capture-mutate.js

@@ -1,4 +1,4 @@
-// @flow @enableTransitivelyFreezeFunctionExpressions:false
+// @flow @enableTransitivelyFreezeFunctionExpressions:false @enableNewMutationAliasingModel:false
 import {setPropertyByKey, Stringify} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-capturing-func-maybealias-captured-mutate.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel:false
 import {makeArray, mutate} from 'shared-runtime';
 
 /**
@@ -56,7 +57,7 @@ export const FIXTURE_ENTRYPOINT = {
 ## Code
 
 ```javascript
-import { c as _c } from "react/compiler-runtime";
+import { c as _c } from "react/compiler-runtime"; // @enableNewMutationAliasingModel:false
 import { makeArray, mutate } from "shared-runtime";
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-capturing-func-maybealias-captured-mutate.ts

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel:false
 import {makeArray, mutate} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-invalid-phi-as-dependency.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel:false
 import {CONST_TRUE, Stringify, mutate, useIdentity} from 'shared-runtime';
 
 /**
@@ -38,7 +39,7 @@ export const FIXTURE_ENTRYPOINT = {
 ## Code
 
 ```javascript
-import { c as _c } from "react/compiler-runtime";
+import { c as _c } from "react/compiler-runtime"; // @enableNewMutationAliasingModel:false
 import { CONST_TRUE, Stringify, mutate, useIdentity } from "shared-runtime";
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-invalid-phi-as-dependency.tsx

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel:false
 import {CONST_TRUE, Stringify, mutate, useIdentity} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-object-expression-computed-key-modified-during-after-construction-hoisted-sequence-expr.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel:false
 import {identity, mutate} from 'shared-runtime';
 
 /**
@@ -39,7 +40,7 @@ export const FIXTURE_ENTRYPOINT = {
 ## Code
 
 ```javascript
-import { c as _c } from "react/compiler-runtime";
+import { c as _c } from "react/compiler-runtime"; // @enableNewMutationAliasingModel:false
 import { identity, mutate } from "shared-runtime";
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-object-expression-computed-key-modified-during-after-construction-hoisted-sequence-expr.js

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel:false
 import {identity, mutate} from 'shared-runtime';
 
 /**

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-ref-prefix-postfix-operator.expect.md

@@ -0,0 +1,132 @@
+
+## Input
+
+```javascript
+import {useRef, useEffect} from 'react';
+
+/**
+ * The postfix increment operator should return the value before incrementing.
+ * ```js
+ * const id = count.current; // 0
+ * count.current = count.current + 1; // 1
+ * return id;
+ * ```
+ * The bug is that we currently increment the value before the expression is evaluated.
+ * This bug does not trigger when the incremented value is a plain primitive.
+ *
+ * Found differences in evaluator results
+ * Non-forget (expected):
+ * (kind: ok) {"count":{"current":0},"updateCountPostfix":"[[ function params=0 ]]","updateCountPrefix":"[[ function params=0 ]]"}
+ * logs: ['id = 0','count = 1']
+ * Forget:
+ * (kind: ok) {"count":{"current":0},"updateCountPostfix":"[[ function params=0 ]]","updateCountPrefix":"[[ function params=0 ]]"}
+ * logs: ['id = 1','count = 1']
+ */
+function useFoo() {
+  const count = useRef(0);
+  const updateCountPostfix = () => {
+    const id = count.current++;
+    return id;
+  };
+  const updateCountPrefix = () => {
+    const id = ++count.current;
+    return id;
+  };
+  useEffect(() => {
+    const id = updateCountPostfix();
+    console.log(`id = ${id}`);
+    console.log(`count = ${count.current}`);
+  }, []);
+  return {count, updateCountPostfix, updateCountPrefix};
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { useRef, useEffect } from "react";
+
+/**
+ * The postfix increment operator should return the value before incrementing.
+ * ```js
+ * const id = count.current; // 0
+ * count.current = count.current + 1; // 1
+ * return id;
+ * ```
+ * The bug is that we currently increment the value before the expression is evaluated.
+ * This bug does not trigger when the incremented value is a plain primitive.
+ *
+ * Found differences in evaluator results
+ * Non-forget (expected):
+ * (kind: ok) {"count":{"current":0},"updateCountPostfix":"[[ function params=0 ]]","updateCountPrefix":"[[ function params=0 ]]"}
+ * logs: ['id = 0','count = 1']
+ * Forget:
+ * (kind: ok) {"count":{"current":0},"updateCountPostfix":"[[ function params=0 ]]","updateCountPrefix":"[[ function params=0 ]]"}
+ * logs: ['id = 1','count = 1']
+ */
+function useFoo() {
+  const $ = _c(5);
+  const count = useRef(0);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = () => {
+      count.current = count.current + 1;
+      const id = count.current;
+      return id;
+    };
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  const updateCountPostfix = t0;
+  let t1;
+  if ($[1] === Symbol.for("react.memo_cache_sentinel")) {
+    t1 = () => {
+      const id_0 = (count.current = count.current + 1);
+      return id_0;
+    };
+    $[1] = t1;
+  } else {
+    t1 = $[1];
+  }
+  const updateCountPrefix = t1;
+  let t2;
+  let t3;
+  if ($[2] === Symbol.for("react.memo_cache_sentinel")) {
+    t2 = () => {
+      const id_1 = updateCountPostfix();
+      console.log(`id = ${id_1}`);
+      console.log(`count = ${count.current}`);
+    };
+    t3 = [];
+    $[2] = t2;
+    $[3] = t3;
+  } else {
+    t2 = $[2];
+    t3 = $[3];
+  }
+  useEffect(t2, t3);
+  let t4;
+  if ($[4] === Symbol.for("react.memo_cache_sentinel")) {
+    t4 = { count, updateCountPostfix, updateCountPrefix };
+    $[4] = t4;
+  } else {
+    t4 = $[4];
+  }
+  return t4;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [],
+};
+
+```
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-ref-prefix-postfix-operator.js

@@ -0,0 +1,42 @@
+import {useRef, useEffect} from 'react';
+
+/**
+ * The postfix increment operator should return the value before incrementing.
+ * ```js
+ * const id = count.current; // 0
+ * count.current = count.current + 1; // 1
+ * return id;
+ * ```
+ * The bug is that we currently increment the value before the expression is evaluated.
+ * This bug does not trigger when the incremented value is a plain primitive.
+ *
+ * Found differences in evaluator results
+ * Non-forget (expected):
+ * (kind: ok) {"count":{"current":0},"updateCountPostfix":"[[ function params=0 ]]","updateCountPrefix":"[[ function params=0 ]]"}
+ * logs: ['id = 0','count = 1']
+ * Forget:
+ * (kind: ok) {"count":{"current":0},"updateCountPostfix":"[[ function params=0 ]]","updateCountPrefix":"[[ function params=0 ]]"}
+ * logs: ['id = 1','count = 1']
+ */
+function useFoo() {
+  const count = useRef(0);
+  const updateCountPostfix = () => {
+    const id = count.current++;
+    return id;
+  };
+  const updateCountPrefix = () => {
+    const id = ++count.current;
+    return id;
+  };
+  useEffect(() => {
+    const id = updateCountPostfix();
+    console.log(`id = ${id}`);
+    console.log(`count = ${count.current}`);
+  }, []);
+  return {count, updateCountPostfix, updateCountPrefix};
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [],
+};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-separate-memoization-due-to-callback-capturing.expect.md

@@ -0,0 +1,138 @@
+
+## Input
+
+```javascript
+// @enableNewMutationAliasingModel:false
+import {ValidateMemoization} from 'shared-runtime';
+
+const Codes = {
+  en: {name: 'English'},
+  ja: {name: 'Japanese'},
+  ko: {name: 'Korean'},
+  zh: {name: 'Chinese'},
+};
+
+function Component(a) {
+  let keys;
+  if (a) {
+    keys = Object.keys(Codes);
+  } else {
+    return null;
+  }
+  const options = keys.map(code => {
+    const country = Codes[code];
+    return {
+      name: country.name,
+      code,
+    };
+  });
+  return (
+    <>
+      <ValidateMemoization inputs={[]} output={keys} onlyCheckCompiled={true} />
+      <ValidateMemoization
+        inputs={[]}
+        output={options}
+        onlyCheckCompiled={true}
+      />
+    </>
+  );
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{a: false}],
+  sequentialRenders: [
+    {a: false},
+    {a: true},
+    {a: true},
+    {a: false},
+    {a: true},
+    {a: false},
+  ],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @enableNewMutationAliasingModel:false
+import { ValidateMemoization } from "shared-runtime";
+
+const Codes = {
+  en: { name: "English" },
+  ja: { name: "Japanese" },
+  ko: { name: "Korean" },
+  zh: { name: "Chinese" },
+};
+
+function Component(a) {
+  const $ = _c(4);
+  let keys;
+  if (a) {
+    let t0;
+    if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+      t0 = Object.keys(Codes);
+      $[0] = t0;
+    } else {
+      t0 = $[0];
+    }
+    keys = t0;
+  } else {
+    return null;
+  }
+  let t0;
+  if ($[1] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = keys.map(_temp);
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  const options = t0;
+  let t1;
+  if ($[2] === Symbol.for("react.memo_cache_sentinel")) {
+    t1 = (
+      <ValidateMemoization inputs={[]} output={keys} onlyCheckCompiled={true} />
+    );
+    $[2] = t1;
+  } else {
+    t1 = $[2];
+  }
+  let t2;
+  if ($[3] === Symbol.for("react.memo_cache_sentinel")) {
+    t2 = (
+      <>
+        {t1}
+        <ValidateMemoization
+          inputs={[]}
+          output={options}
+          onlyCheckCompiled={true}
+        />
+      </>
+    );
+    $[3] = t2;
+  } else {
+    t2 = $[3];
+  }
+  return t2;
+}
+function _temp(code) {
+  const country = Codes[code];
+  return { name: country.name, code };
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{ a: false }],
+  sequentialRenders: [
+    { a: false },
+    { a: true },
+    { a: true },
+    { a: false },
+    { a: true },
+    { a: false },
+  ],
+};
+
+```
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/bug-separate-memoization-due-to-callback-capturing.js

@@ -0,0 +1,48 @@
+// @enableNewMutationAliasingModel:false
+import {ValidateMemoization} from 'shared-runtime';
+
+const Codes = {
+  en: {name: 'English'},
+  ja: {name: 'Japanese'},
+  ko: {name: 'Korean'},
+  zh: {name: 'Chinese'},
+};
+
+function Component(a) {
+  let keys;
+  if (a) {
+    keys = Object.keys(Codes);
+  } else {
+    return null;
+  }
+  const options = keys.map(code => {
+    const country = Codes[code];
+    return {
+      name: country.name,
+      code,
+    };
+  });
+  return (
+    <>
+      <ValidateMemoization inputs={[]} output={keys} onlyCheckCompiled={true} />
+      <ValidateMemoization
+        inputs={[]}
+        output={options}
+        onlyCheckCompiled={true}
+      />
+    </>
+  );
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{a: false}],
+  sequentialRenders: [
+    {a: false},
+    {a: true},
+    {a: true},
+    {a: false},
+    {a: true},
+    {a: false},
+  ],
+};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capturing-function-alias-computed-load-2-iife.expect.md

@@ -25,17 +25,25 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function bar(a) {
-  const $ = _c(2);
-  let y;
+  const $ = _c(4);
+  let t0;
   if ($[0] !== a) {
-    const x = [a];
+    t0 = [a];
+    $[0] = a;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  const x = t0;
+  let y;
+  if ($[2] !== x[0][1]) {
     y = {};
 
     y = x[0][1];
-    $[0] = a;
-    $[1] = y;
+    $[2] = x[0][1];
+    $[3] = y;
   } else {
-    y = $[1];
+    y = $[3];
   }
   return y;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capturing-function-alias-computed-load-3-iife.expect.md

@@ -29,20 +29,29 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function bar(a, b) {
-  const $ = _c(3);
-  let y;
+  const $ = _c(6);
+  let t0;
   if ($[0] !== a || $[1] !== b) {
-    const x = [a, b];
+    t0 = [a, b];
+    $[0] = a;
+    $[1] = b;
+    $[2] = t0;
+  } else {
+    t0 = $[2];
+  }
+  const x = t0;
+  let y;
+  if ($[3] !== x[0][1] || $[4] !== x[1][0]) {
     y = {};
     let t = {};
 
     y = x[0][1];
     t = x[1][0];
-    $[0] = a;
-    $[1] = b;
-    $[2] = y;
+    $[3] = x[0][1];
+    $[4] = x[1][0];
+    $[5] = y;
   } else {
-    y = $[2];
+    y = $[5];
   }
   return y;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capturing-function-alias-computed-load-4-iife.expect.md

@@ -25,17 +25,25 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function bar(a) {
-  const $ = _c(2);
-  let y;
+  const $ = _c(4);
+  let t0;
   if ($[0] !== a) {
-    const x = [a];
+    t0 = [a];
+    $[0] = a;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  const x = t0;
+  let y;
+  if ($[2] !== x[0].a[1]) {
     y = {};
 
     y = x[0].a[1];
-    $[0] = a;
-    $[1] = y;
+    $[2] = x[0].a[1];
+    $[3] = y;
   } else {
-    y = $[1];
+    y = $[3];
   }
   return y;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capturing-function-alias-computed-load-iife.expect.md

@@ -24,17 +24,25 @@ export const FIXTURE_ENTRYPOINT = {
 ```javascript
 import { c as _c } from "react/compiler-runtime";
 function bar(a) {
-  const $ = _c(2);
-  let y;
+  const $ = _c(4);
+  let t0;
   if ($[0] !== a) {
-    const x = [a];
+    t0 = [a];
+    $[0] = a;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  const x = t0;
+  let y;
+  if ($[2] !== x[0]) {
     y = {};
 
     y = x[0];
-    $[0] = a;
-    $[1] = y;
+    $[2] = x[0];
+    $[3] = y;
   } else {
-    y = $[1];
+    y = $[3];
   }
   return y;
 }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/custom-opt-out-directive.expect.md

@@ -0,0 +1,35 @@
+
+## Input
+
+```javascript
+// @customOptOutDirectives:["use todo memo"]
+function Component() {
+  'use todo memo';
+  return <div>hello world!</div>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};
+
+```
+
+## Code
+
+```javascript
+// @customOptOutDirectives:["use todo memo"]
+function Component() {
+  "use todo memo";
+  return <div>hello world!</div>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};
+
+```
+      
+### Eval output
+(kind: ok) <div>hello world!</div>

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/custom-opt-out-directive.tsx

@@ -0,0 +1,10 @@
+// @customOptOutDirectives:["use todo memo"]
+function Component() {
+  'use todo memo';
+  return <div>hello world!</div>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [],
+};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/dominator.expect.md

@@ -67,8 +67,7 @@ function Component(props) {
     case "b": {
       break bb1;
     }
-    case "c": {
-    }
+    case "c":
     default: {
       x = 6;
     }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel:false
 function Component() {
   const foo = () => {
     someGlobal = true;
@@ -15,13 +16,13 @@ function Component() {
 ## Error
 
 ```
-  1 | function Component() {
-  2 |   const foo = () => {
-> 3 |     someGlobal = true;
-    |     ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (3:3)
-  4 |   };
-  5 |   return <div {...foo} />;
-  6 | }
+  2 | function Component() {
+  3 |   const foo = () => {
+> 4 |     someGlobal = true;
+    |     ^^^^^^^^^^ InvalidReact: Unexpected reassignment of a variable which was defined outside of the component. Components and hooks should be pure and side-effect free, but variable reassignment is a form of side-effect. If this variable is used in rendering, use useState instead. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#side-effects-must-run-outside-of-render) (4:4)
+  5 |   };
+  6 |   return <div {...foo} />;
+  7 | }
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-jsx-spread-attribute.js

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel:false
 function Component() {
   const foo = () => {
     someGlobal = true;

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.bug-old-inference-false-positive-ref-validation-in-use-effect.expect.md

@@ -0,0 +1,58 @@
+
+## Input
+
+```javascript
+// @validateNoFreezingKnownMutableFunctions @enableNewMutationAliasingModel:false
+
+import {useCallback, useEffect, useRef} from 'react';
+import {useHook} from 'shared-runtime';
+
+function Component() {
+  const params = useHook();
+  const update = useCallback(
+    partialParams => {
+      const nextParams = {
+        ...params,
+        ...partialParams,
+      };
+      nextParams.param = 'value';
+      console.log(nextParams);
+    },
+    [params]
+  );
+  const ref = useRef(null);
+  useEffect(() => {
+    if (ref.current === null) {
+      update();
+    }
+  }, [update]);
+
+  return 'ok';
+}
+
+```
+
+
+## Error
+
+```
+  18 |   );
+  19 |   const ref = useRef(null);
+> 20 |   useEffect(() => {
+     |             ^^^^^^^
+> 21 |     if (ref.current === null) {
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 22 |       update();
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 23 |     }
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 24 |   }, [update]);
+     | ^^^^ InvalidReact: This argument is a function which may reassign or mutate local variables after render, which can cause inconsistent behavior on subsequent renders. Consider using state instead (20:24)
+
+InvalidReact: The function modifies a local variable here (14:14)
+  25 |
+  26 |   return 'ok';
+  27 | }
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.bug-old-inference-false-positive-ref-validation-in-use-effect.js

@@ -0,0 +1,27 @@
+// @validateNoFreezingKnownMutableFunctions @enableNewMutationAliasingModel:false
+
+import {useCallback, useEffect, useRef} from 'react';
+import {useHook} from 'shared-runtime';
+
+function Component() {
+  const params = useHook();
+  const update = useCallback(
+    partialParams => {
+      const nextParams = {
+        ...params,
+        ...partialParams,
+      };
+      nextParams.param = 'value';
+      console.log(nextParams);
+    },
+    [params]
+  );
+  const ref = useRef(null);
+  useEffect(() => {
+    if (ref.current === null) {
+      update();
+    }
+  }, [update]);
+
+  return 'ok';
+}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.hook-call-freezes-captured-identifier.expect.md

@@ -32,7 +32,7 @@ export const FIXTURE_ENTRYPOINT = {
   11 |   });
   12 |
 > 13 |   x.value += count;
-     |   ^ InvalidReact: This mutates a variable that React considers immutable (13:13)
+     |   ^ InvalidReact: Updating a value previously passed as an argument to a hook is not allowed. Consider moving the mutation before calling the hook (13:13)
   14 |   return <Stringify x={x} cb={cb} />;
   15 | }
   16 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.hook-call-freezes-captured-memberexpr.expect.md

@@ -32,7 +32,7 @@ export const FIXTURE_ENTRYPOINT = {
   11 |   });
   12 |
 > 13 |   x.value += count;
-     |   ^ InvalidReact: This mutates a variable that React considers immutable (13:13)
+     |   ^ InvalidReact: Updating a value previously passed as an argument to a hook is not allowed. Consider moving the mutation before calling the hook (13:13)
   14 |   return <Stringify x={x} cb={cb} />;
   15 | }
   16 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.hook-ref-value.expect.md

@@ -24,8 +24,6 @@ export const FIXTURE_ENTRYPOINT = {
   4 |   const ref = useRef();
 > 5 |   useEffect(() => {}, [ref.current]);
     |                        ^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (5:5)
-
-InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (5:5)
   6 | }
   7 |
   8 | export const FIXTURE_ENTRYPOINT = {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-access-ref-during-render.expect.md

@@ -19,6 +19,8 @@ function Component(props) {
   3 |   const ref = useRef(null);
 > 4 |   const value = ref.current;
     |                 ^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (4:4)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef). Cannot access ref value `value` (5:5)
   5 |   return value;
   6 | }
   7 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-aliased-ref-in-callback-invoked-during-render-.expect.md

@@ -19,12 +19,17 @@ function Component(props) {
 ## Error
 
 ```
-   7 |     return <Foo item={item} current={current} />;
-   8 |   };
->  9 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
-     |                                  ^^^^^^^^^^^^^^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (9:9)
-  10 | }
-  11 |
+  4 |   const renderItem = item => {
+  5 |     const aliasedRef = ref;
+> 6 |     const current = aliasedRef.current;
+    |                     ^^^^^^^^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (6:6)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef). Cannot access ref value `current` (7:7)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (7:7)
+  7 |     return <Foo item={item} current={current} />;
+  8 |   };
+  9 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-disallow-mutating-refs-in-render-transitive.expect.md

@@ -21,15 +21,13 @@ function Component() {
 ## Error
 
 ```
-   7 |   };
-   8 |   const changeRef = setRef;
->  9 |   changeRef();
-     |   ^^^^^^^^^ InvalidReact: This function accesses a ref value (the `current` property), which may not be accessed during render. (https://react.dev/reference/react/useRef) (9:9)
-
-InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (9:9)
-  10 |
-  11 |   return <button ref={ref} />;
-  12 | }
+  4 |
+  5 |   const setRef = () => {
+> 6 |     ref.current = false;
+    |     ^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (6:6)
+  7 |   };
+  8 |   const changeRef = setRef;
+  9 |   changeRef();
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-hoisting-setstate.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel
 import {useEffect, useState} from 'react';
 import {Stringify} from 'shared-runtime';
 
@@ -33,45 +34,19 @@ export const FIXTURE_ENTRYPOINT = {
 
 ```
 
-## Code
 
-```javascript
-import { c as _c } from "react/compiler-runtime";
-import { useEffect, useState } from "react";
-import { Stringify } from "shared-runtime";
-
-function Foo() {
-  const $ = _c(3);
-  let t0;
-  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
-    t0 = [];
-    $[0] = t0;
-  } else {
-    t0 = $[0];
-  }
-  useEffect(() => setState(2), t0);
-
-  const [state, t1] = useState(0);
-  const setState = t1;
-  let t2;
-  if ($[1] !== state) {
-    t2 = <Stringify state={state} />;
-    $[1] = state;
-    $[2] = t2;
-  } else {
-    t2 = $[2];
-  }
-  return t2;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: Foo,
-  params: [{}],
-  sequentialRenders: [{}, {}],
-};
+## Error
 
 ```
-      
-### Eval output
-(kind: ok) <div>{"state":2}</div>
-<div>{"state":2}</div>
+  17 |    * $2 = Function context=setState
+  18 |    */
+> 19 |   useEffect(() => setState(2), []);
+     |                   ^^^^^^^^ InvalidReact: This variable is accessed before it is declared, which may prevent it from updating as the assigned value changes over time. Variable `setState` is accessed before it is declared (19:19)
+
+InvalidReact: This variable is accessed before it is declared, which prevents the earlier access from updating when this value changes over time. Variable `setState` is accessed before it is declared (21:21)
+  20 |
+  21 |   const [state, setState] = useState(0);
+  22 |   return <Stringify state={state} />;
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-hoisting-setstate.js

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel
 import {useEffect, useState} from 'react';
 import {Stringify} from 'shared-runtime';
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-hook-function-argument-mutates-local-variable.expect.md

@@ -24,7 +24,7 @@ function useFoo() {
 > 6 |     cache.set('key', 'value');
     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 > 7 |   });
-    | ^^^^ InvalidReact: This argument is a function which modifies local variables when called, which can bypass memoization and cause the UI not to update. Functions that are returned from hooks, passed as arguments to hooks, or passed as props to components may not mutate local variables (5:7)
+    | ^^^^ InvalidReact: This argument is a function which may reassign or mutate local variables after render, which can cause inconsistent behavior on subsequent renders. Consider using state instead (5:7)
 
 InvalidReact: The function modifies a local variable here (6:6)
   8 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-impure-functions-in-render.expect.md

@@ -20,7 +20,7 @@ function Component() {
   2 |
   3 | function Component() {
 > 4 |   const date = Date.now();
-    |                ^^^^^^^^ InvalidReact: Calling an impure function can produce unstable results. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent). `Date.now` is an impure function whose results may change on every call (4:4)
+    |                ^^^^^^^^^^ InvalidReact: Calling an impure function can produce unstable results. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent). `Date.now` is an impure function whose results may change on every call (4:4)
 
 InvalidReact: Calling an impure function can produce unstable results. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent). `performance.now` is an impure function whose results may change on every call (5:5)
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-jsx-captures-context-variable.expect.md

@@ -0,0 +1,62 @@
+
+## Input
+
+```javascript
+// @enableNewMutationAliasingModel
+import {Stringify, useIdentity} from 'shared-runtime';
+
+function Component({prop1, prop2}) {
+  'use memo';
+
+  const data = useIdentity(
+    new Map([
+      [0, 'value0'],
+      [1, 'value1'],
+    ])
+  );
+  let i = 0;
+  const items = [];
+  items.push(
+    <Stringify
+      key={i}
+      onClick={() => data.get(i) + prop1}
+      shouldInvokeFns={true}
+    />
+  );
+  i = i + 1;
+  items.push(
+    <Stringify
+      key={i}
+      onClick={() => data.get(i) + prop2}
+      shouldInvokeFns={true}
+    />
+  );
+  return <>{items}</>;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{prop1: 'prop1', prop2: 'prop2'}],
+  sequentialRenders: [
+    {prop1: 'prop1', prop2: 'prop2'},
+    {prop1: 'prop1', prop2: 'prop2'},
+    {prop1: 'changed', prop2: 'prop2'},
+  ],
+};
+
+```
+
+
+## Error
+
+```
+  20 |     />
+  21 |   );
+> 22 |   i = i + 1;
+     |   ^ InvalidReact: Updating a value used previously in JSX is not allowed. Consider moving the mutation before the JSX. Found mutation of `i` (22:22)
+  23 |   items.push(
+  24 |     <Stringify
+  25 |       key={i}
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-jsx-captures-context-variable.js

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel
 import {Stringify, useIdentity} from 'shared-runtime';
 
 function Component({prop1, prop2}) {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-non-imported-reanimated-shared-value-writes.expect.md

@@ -27,7 +27,7 @@ function SomeComponent() {
    9 |   return (
   10 |     <Button
 > 11 |       onPress={() => (sharedVal.value = Math.random())}
-     |                       ^^^^^^^^^ InvalidReact: Mutating a value returned from a function whose return value should not be mutated. Found mutation of `sharedVal` (11:11)
+     |                       ^^^^^^^^^ InvalidReact: Updating a value returned from a hook is not allowed. Consider moving the mutation into the hook where the value is constructed. Found mutation of `sharedVal` (11:11)
   12 |       title="Randomize"
   13 |     />
   14 |   );

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-pass-mutable-function-as-prop.expect.md

@@ -20,7 +20,7 @@ function Component() {
   5 |     cache.set('key', 'value');
   6 |   };
 > 7 |   return <Foo fn={fn} />;
-    |                   ^^ InvalidReact: This argument is a function which modifies local variables when called, which can bypass memoization and cause the UI not to update. Functions that are returned from hooks, passed as arguments to hooks, or passed as props to components may not mutate local variables (7:7)
+    |                   ^^ InvalidReact: This argument is a function which may reassign or mutate local variables after render, which can cause inconsistent behavior on subsequent renders. Consider using state instead (7:7)
 
 InvalidReact: The function modifies a local variable here (5:5)
   8 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-read-ref-prop-in-render-destructure.expect.md

@@ -18,6 +18,10 @@ function Component({ref}) {
   2 | function Component({ref}) {
 > 3 |   const value = ref.current;
     |                 ^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (3:3)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef). Cannot access ref value `value` (4:4)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (4:4)
   4 |   return <div>{value}</div>;
   5 | }
   6 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-read-ref-prop-in-render-property-load.expect.md

@@ -18,6 +18,10 @@ function Component(props) {
   2 | function Component(props) {
 > 3 |   const value = props.ref.current;
     |                 ^^^^^^^^^^^^^^^^^ InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (3:3)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef). Cannot access ref value `value` (4:4)
+
+InvalidReact: Ref values (the `current` property) may not be accessed during render. (https://react.dev/reference/react/useRef) (4:4)
   4 |   return <div>{value}</div>;
   5 | }
   6 |