[compiler] update fixtures

The previous error message was generic, because the old style function
signature didn't support a way to specify a reason alongside a freeze
effect. This meant we could only say why a value was frozen for
instructions, but not hooks which use function signatures. By defining a
new aliasing signature for custom hooks we can specify a reason and
provide a better error message.

---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/facebook/react/pull/33513).
* #33571
* #33558
* #33547
* #33543
* #33533
* #33532
* #33530
* #33526
* #33522
* #33518
* #33514
* __->__ #33513

.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 +280,35 @@ jobs:
         if: steps.node_modules.outputs.cache-hit != 'true'
       - run: yarn test ${{ matrix.params }} --ci --shard=${{ matrix.shard }}
 
+  # Hardcoded to improve parallelism
+  test-linter:
+    name: Test eslint-plugin-react-hooks
+    needs: [runtime_compiler_node_modules_cache]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version-file: '.nvmrc'
+          cache: yarn
+          cache-dependency-path:  |
+            yarn.lock
+            compiler/yarn.lock
+      - name: Restore cached node_modules
+        uses: actions/cache@v4
+        id: node_modules
+        with:
+          path: |
+            **/node_modules
+          key: runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-${{ hashFiles('yarn.lock', 'compiler/yarn.lock') }}
+          restore-keys: |
+            runtime-and-compiler-node_modules-v6-${{ runner.arch }}-${{ runner.os }}-
+            runtime-and-compiler-node_modules-v6-
+      - run: yarn install --frozen-lockfile
+        if: steps.node_modules.outputs.cache-hit != 'true'
+      - run: ./scripts/react-compiler/build-compiler.sh && ./scripts/react-compiler/link-compiler.sh
+      - run: yarn workspace eslint-plugin-react-hooks test
+        
   # ----- BUILD -----
   build_and_lint:
     name: yarn build and lint

.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.'
@@ -61,10 +72,36 @@ 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

.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/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/.gitignore

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

compiler/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

@@ -37,6 +37,14 @@ const PanicThresholdOptionsSchema = z.enum([
 ]);
 
 export type PanicThresholdOptions = z.infer<typeof PanicThresholdOptionsSchema>;
+const DynamicGatingOptionsSchema = z.object({
+  source: z.string(),
+});
+export type DynamicGatingOptions = z.infer<typeof DynamicGatingOptionsSchema>;
+const CustomOptOutDirectiveSchema = z
+  .nullable(z.array(z.string()))
+  .default(null);
+type CustomOptOutDirective = z.infer<typeof CustomOptOutDirectiveSchema>;
 
 export type PluginOptions = {
   environment: EnvironmentConfig;
@@ -65,6 +73,28 @@ export type PluginOptions = {
    */
   gating: ExternalFunction | null;
 
+  /**
+   * If specified, this enables dynamic gating which matches `use memo if(...)`
+   * directives.
+   *
+   * Example usage:
+   * ```js
+   * // @dynamicGating:{"source":"myModule"}
+   * export function MyComponent() {
+   *   'use memo if(isEnabled)';
+   *    return <div>...</div>;
+   * }
+   * ```
+   * This will emit:
+   * ```js
+   * import {isEnabled} from 'myModule';
+   * export const MyComponent = isEnabled()
+   *   ? <optimized version>
+   *   : <original version>;
+   * ```
+   */
+  dynamicGating: DynamicGatingOptions | null;
+
   panicThreshold: PanicThresholdOptions;
 
   /*
@@ -106,6 +136,11 @@ export type PluginOptions = {
    */
   ignoreUseNoForget: boolean;
 
+  /**
+   * Unstable / do not use
+   */
+  customOptOutDirectives: CustomOptOutDirective;
+
   sources: Array<string> | ((filename: string) => boolean) | null;
 
   /**
@@ -244,6 +279,7 @@ export const defaultOptions: PluginOptions = {
   logger: null,
   gating: null,
   noEmit: false,
+  dynamicGating: null,
   eslintSuppressionRules: null,
   flowSuppressions: true,
   ignoreUseNoForget: false,
@@ -251,6 +287,7 @@ export const defaultOptions: PluginOptions = {
     return filename.indexOf('node_modules') === -1;
   },
   enableReanimatedCheck: true,
+  customOptOutDirectives: null,
   target: '19',
 } as const;
 
@@ -292,6 +329,40 @@ export function parsePluginOptions(obj: unknown): PluginOptions {
           }
           break;
         }
+        case 'dynamicGating': {
+          if (value == null) {
+            parsedOptions[key] = null;
+          } else {
+            const result = DynamicGatingOptionsSchema.safeParse(value);
+            if (result.success) {
+              parsedOptions[key] = result.data;
+            } else {
+              CompilerError.throwInvalidConfig({
+                reason:
+                  'Could not parse dynamic gating. Update React Compiler config to fix the error',
+                description: `${fromZodError(result.error)}`,
+                loc: null,
+                suggestions: null,
+              });
+            }
+          }
+          break;
+        }
+        case 'customOptOutDirectives': {
+          const result = CustomOptOutDirectiveSchema.safeParse(value);
+          if (result.success) {
+            parsedOptions[key] = result.data;
+          } else {
+            CompilerError.throwInvalidConfig({
+              reason:
+                'Could not parse custom opt out directives. Update React Compiler config to fix the error',
+              description: `${fromZodError(result.error)}`,
+              loc: null,
+              suggestions: null,
+            });
+          }
+          break;
+        }
         default: {
           parsedOptions[key] = value;
         }

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

@@ -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) {
@@ -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

@@ -12,7 +12,7 @@ import {
   CompilerErrorDetail,
   ErrorSeverity,
 } from '../CompilerError';
-import {ReactFunctionType} from '../HIR/Environment';
+import {ExternalFunction, ReactFunctionType} from '../HIR/Environment';
 import {CodegenFunction} from '../ReactiveScopes';
 import {isComponentDeclaration} from '../Utils/ComponentDeclaration';
 import {isHookDeclaration} from '../Utils/HookDeclaration';
@@ -31,6 +31,7 @@ import {
   suppressionsToCompilerError,
 } from './Suppression';
 import {GeneratedSource} from '../HIR';
+import {Err, Ok, Result} from '../Utils/Result';
 
 export type CompilerPass = {
   opts: PluginOptions;
@@ -40,26 +41,102 @@ export type CompilerPass = {
 };
 export const OPT_IN_DIRECTIVES = new Set(['use forget', 'use memo']);
 export const OPT_OUT_DIRECTIVES = new Set(['use no forget', 'use no memo']);
+const DYNAMIC_GATING_DIRECTIVE = new RegExp('^use memo if\\(([^\\)]*)\\)$');
 
-export function findDirectiveEnablingMemoization(
+export function tryFindDirectiveEnablingMemoization(
   directives: Array<t.Directive>,
-): t.Directive | null {
-  return (
-    directives.find(directive =>
-      OPT_IN_DIRECTIVES.has(directive.value.value),
-    ) ?? null
+  opts: PluginOptions,
+): Result<t.Directive | null, CompilerError> {
+  const optIn = directives.find(directive =>
+    OPT_IN_DIRECTIVES.has(directive.value.value),
   );
+  if (optIn != null) {
+    return Ok(optIn);
+  }
+  const dynamicGating = findDirectivesDynamicGating(directives, opts);
+  if (dynamicGating.isOk()) {
+    return Ok(dynamicGating.unwrap()?.directive ?? null);
+  } else {
+    return Err(dynamicGating.unwrapErr());
+  }
 }
 
 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),
     ) ?? null
   );
 }
+function findDirectivesDynamicGating(
+  directives: Array<t.Directive>,
+  opts: PluginOptions,
+): Result<
+  {
+    gating: ExternalFunction;
+    directive: t.Directive;
+  } | null,
+  CompilerError
+> {
+  if (opts.dynamicGating === null) {
+    return Ok(null);
+  }
+  const errors = new CompilerError();
+  const result: Array<{directive: t.Directive; match: string}> = [];
+
+  for (const directive of directives) {
+    const maybeMatch = DYNAMIC_GATING_DIRECTIVE.exec(directive.value.value);
+    if (maybeMatch != null && maybeMatch[1] != null) {
+      if (t.isValidIdentifier(maybeMatch[1])) {
+        result.push({directive, match: maybeMatch[1]});
+      } else {
+        errors.push({
+          reason: `Dynamic gating directive is not a valid JavaScript identifier`,
+          description: `Found '${directive.value.value}'`,
+          severity: ErrorSeverity.InvalidReact,
+          loc: directive.loc ?? null,
+          suggestions: null,
+        });
+      }
+    }
+  }
+  if (errors.hasErrors()) {
+    return Err(errors);
+  } else if (result.length > 1) {
+    const error = new CompilerError();
+    error.push({
+      reason: `Multiple dynamic gating directives found`,
+      description: `Expected a single directive but found [${result
+        .map(r => r.directive.value.value)
+        .join(', ')}]`,
+      severity: ErrorSeverity.InvalidReact,
+      loc: result[0].directive.loc ?? null,
+      suggestions: null,
+    });
+    return Err(error);
+  } else if (result.length === 1) {
+    return Ok({
+      gating: {
+        source: opts.dynamicGating.source,
+        importSpecifierName: result[0].match,
+      },
+      directive: result[0].directive,
+    });
+  } else {
+    return Ok(null);
+  }
+}
 
 function isCriticalError(err: unknown): boolean {
   return !(err instanceof CompilerError) || err.isCritical();
@@ -326,7 +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(
@@ -477,13 +555,36 @@ function processFn(
   fnType: ReactFunctionType,
   programContext: ProgramContext,
 ): null | CodegenFunction {
-  let directives;
+  let directives: {
+    optIn: t.Directive | null;
+    optOut: t.Directive | null;
+  };
   if (fn.node.body.type !== 'BlockStatement') {
-    directives = {optIn: null, optOut: null};
-  } else {
     directives = {
-      optIn: findDirectiveEnablingMemoization(fn.node.body.directives),
-      optOut: findDirectiveDisablingMemoization(fn.node.body.directives),
+      optIn: null,
+      optOut: null,
+    };
+  } else {
+    const optIn = tryFindDirectiveEnablingMemoization(
+      fn.node.body.directives,
+      programContext.opts,
+    );
+    if (optIn.isErr()) {
+      /**
+       * If parsing opt-in directive fails, it's most likely that React Compiler
+       * was not tested or rolled out on this function. In that case, we handle
+       * the error and fall back to the safest option which is to not optimize
+       * the function.
+       */
+      handleError(optIn.unwrapErr(), programContext, fn.node.loc ?? null);
+      return null;
+    }
+    directives = {
+      optIn: optIn.unwrapOr(null),
+      optOut: findDirectiveDisablingMemoization(
+        fn.node.body.directives,
+        programContext.opts,
+      ),
     };
   }
 
@@ -659,25 +760,31 @@ function applyCompiledFunctions(
   pass: CompilerPass,
   programContext: ProgramContext,
 ): void {
-  const referencedBeforeDeclared =
-    pass.opts.gating != null
-      ? getFunctionReferencedBeforeDeclarationAtTopLevel(program, compiledFns)
-      : null;
+  let referencedBeforeDeclared = null;
   for (const result of compiledFns) {
     const {kind, originalFn, compiledFn} = result;
     const transformedFn = createNewFunctionNode(originalFn, compiledFn);
     programContext.alreadyCompiled.add(transformedFn);
 
-    if (referencedBeforeDeclared != null && kind === 'original') {
-      CompilerError.invariant(pass.opts.gating != null, {
-        reason: "Expected 'gating' import to be present",
-        loc: null,
-      });
+    let dynamicGating: ExternalFunction | null = null;
+    if (originalFn.node.body.type === 'BlockStatement') {
+      const result = findDirectivesDynamicGating(
+        originalFn.node.body.directives,
+        pass.opts,
+      );
+      if (result.isOk()) {
+        dynamicGating = result.unwrap()?.gating ?? null;
+      }
+    }
+    const functionGating = dynamicGating ?? pass.opts.gating;
+    if (kind === 'original' && functionGating != null) {
+      referencedBeforeDeclared ??=
+        getFunctionReferencedBeforeDeclarationAtTopLevel(program, compiledFns);
       insertGatedFunctionDeclaration(
         originalFn,
         transformedFn,
         programContext,
-        pass.opts.gating,
+        functionGating,
         referencedBeforeDeclared.has(result),
       );
     } else {
@@ -733,8 +840,13 @@ function getReactFunctionType(
 ): ReactFunctionType | null {
   const hookPattern = pass.opts.environment.hookPattern;
   if (fn.node.body.type === 'BlockStatement') {
-    if (findDirectiveEnablingMemoization(fn.node.body.directives) != null)
+    const optInDirectives = tryFindDirectiveEnablingMemoization(
+      fn.node.body.directives,
+      pass.opts,
+    );
+    if (optInDirectives.unwrapOr(null) != null) {
       return getComponentOrHookLike(fn, hookPattern) ?? 'Other';
+    }
   }
 
   // Component and hook declarations are known components/hooks

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 +219,10 @@ export function lower(
   return Ok({
     id,
     params,
-    fnType: parent == null ? env.fnType : 'Other',
+    fnType: bindings == null ? env.fnType : 'Other',
     returnTypeAnnotation: null, // TODO: extract the actual return type node if present
     returnType: makeType(),
+    returns: createTemporaryPlace(env, func.node.loc ?? GeneratedSource),
     body: builder.build(),
     context,
     generator: func.node.generator === true,
@@ -225,6 +230,7 @@ export function lower(
     loc: func.node.loc ?? GeneratedSource,
     env,
     effects: null,
+    aliasingEffects: null,
     directives,
   });
 }
@@ -285,6 +291,7 @@ function lowerStatement(
         loc: stmt.node.loc ?? GeneratedSource,
         value,
         id: makeInstructionId(0),
+        effects: null,
       };
       builder.terminate(terminal, 'block');
       return;
@@ -1235,6 +1242,7 @@ function lowerStatement(
           kind: 'Debugger',
           loc,
         },
+        effects: null,
         loc,
       });
       return;
@@ -1892,6 +1900,7 @@ function lowerExpression(
           place: leftValue,
           loc: exprLoc,
         },
+        effects: null,
         loc: exprLoc,
       });
       builder.terminateWithContinuation(
@@ -2827,6 +2836,7 @@ function lowerOptionalCallExpression(
           args,
           loc,
         },
+        effects: null,
         loc,
       });
     } else {
@@ -2840,6 +2850,7 @@ function lowerOptionalCallExpression(
           args,
           loc,
         },
+        effects: null,
         loc,
       });
     }
@@ -3417,7 +3428,7 @@ function lowerFunction(
     | t.ObjectMethod
   >,
 ): LoweredFunction | null {
-  const componentScope: Scope = builder.parentFunction.scope;
+  const componentScope: Scope = builder.environment.parentFunction.scope;
   const capturedContext = gatherCapturedContext(expr, componentScope);
 
   /*
@@ -3432,8 +3443,7 @@ 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 +3466,7 @@ function lowerExpressionToTemporary(
   return lowerValueToTemporary(builder, value);
 }
 
-function lowerValueToTemporary(
+export function lowerValueToTemporary(
   builder: HIRBuilder,
   value: InstructionValue,
 ): Place {
@@ -3466,9 +3476,10 @@ 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 +4162,11 @@ 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 +4175,8 @@ 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 +4219,15 @@ 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 +4264,7 @@ 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

@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {Effect, ValueKind, ValueReason} from './HIR';
+import {Effect, makeIdentifierId, ValueKind, ValueReason} from './HIR';
 import {
   BUILTIN_SHAPES,
   BuiltInArrayId,
@@ -17,6 +17,7 @@ import {
   BuiltInSetId,
   BuiltInUseActionStateId,
   BuiltInUseContextHookId,
+  BuiltInUseEffectEventId,
   BuiltInUseEffectHookId,
   BuiltInUseInsertionEffectHookId,
   BuiltInUseLayoutEffectHookId,
@@ -27,11 +28,13 @@ import {
   BuiltInUseTransitionId,
   BuiltInWeakMapId,
   BuiltInWeakSetId,
+  BuiltinEffectEventId,
   ReanimatedSharedValueId,
   ShapeRegistry,
   addFunction,
   addHook,
   addObject,
+  signatureArgument,
 } from './ObjectShape';
 import {BuiltInType, ObjectType, PolyType} from './Types';
 import {TypeConfig} from './TypeSchema';
@@ -642,6 +645,41 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         calleeEffect: Effect.Read,
         hookKind: 'useEffect',
         returnValueKind: ValueKind.Frozen,
+        aliasing: {
+          receiver: makeIdentifierId(0),
+          params: [],
+          rest: makeIdentifierId(1),
+          returns: makeIdentifierId(2),
+          temporaries: [signatureArgument(3)],
+          effects: [
+            // Freezes the function and deps
+            {
+              kind: 'Freeze',
+              value: signatureArgument(1),
+              reason: ValueReason.Effect,
+            },
+            // Internally creates an effect object that captures the function and deps
+            {
+              kind: 'Create',
+              into: signatureArgument(3),
+              value: ValueKind.Frozen,
+              reason: ValueReason.KnownReturnSignature,
+            },
+            // The effect stores the function and dependencies
+            {
+              kind: 'Capture',
+              from: signatureArgument(1),
+              into: signatureArgument(3),
+            },
+            // Returns undefined
+            {
+              kind: 'Create',
+              into: signatureArgument(2),
+              value: ValueKind.Primitive,
+              reason: ValueReason.KnownReturnSignature,
+            },
+          ],
+        },
       },
       BuiltInUseEffectHookId,
     ),
@@ -722,6 +760,27 @@ 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(

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;
 };
 
@@ -278,12 +280,14 @@ export type HIRFunction = {
   params: Array<Place | SpreadPattern>;
   returnTypeAnnotation: t.FlowType | t.TSType | null;
   returnType: Type;
+  returns: Place;
   context: Array<Place>;
   effects: Array<FunctionEffect> | null;
   body: HIR;
   generator: boolean;
   async: boolean;
   directives: Array<string>;
+  aliasingEffects?: Array<AliasingEffect> | null;
 };
 
 export type FunctionEffect =
@@ -449,6 +453,7 @@ export type ReturnTerminal = {
   value: Place;
   id: InstructionId;
   fallthrough?: never;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type GotoTerminal = {
@@ -609,6 +614,7 @@ export type MaybeThrowTerminal = {
   id: InstructionId;
   loc: SourceLocation;
   fallthrough?: never;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type ReactiveScopeTerminal = {
@@ -645,12 +651,14 @@ export type Instruction = {
   lvalue: Place;
   value: InstructionValue;
   loc: SourceLocation;
+  effects: Array<AliasingEffect> | null;
 };
 
 export type TInstruction<T extends InstructionValue> = {
   id: InstructionId;
   lvalue: Place;
   value: T;
+  effects: Array<AliasingEffect> | null;
   loc: SourceLocation;
 };
 
@@ -1380,6 +1388,21 @@ 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`.
    */
@@ -1568,6 +1591,18 @@ 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;
 };
 
@@ -1773,6 +1808,13 @@ 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

@@ -6,10 +6,21 @@
  */
 
 import {CompilerError} from '../CompilerError';
-import {Effect, ValueKind, ValueReason} from './HIR';
+import {AliasingSignature} from '../Inference/AliasingEffects';
+import {
+  Effect,
+  GeneratedSource,
+  makeDeclarationId,
+  makeIdentifierId,
+  makeInstructionId,
+  Place,
+  ValueKind,
+  ValueReason,
+} from './HIR';
 import {
   BuiltInType,
   FunctionType,
+  makeType,
   ObjectType,
   PolyType,
   PrimitiveType,
@@ -131,6 +142,7 @@ export type HookKind =
   | 'useCallback'
   | 'useTransition'
   | 'useImperativeHandle'
+  | 'useEffectEvent'
   | 'Custom';
 
 /*
@@ -179,6 +191,9 @@ export type FunctionSignature = {
   impure?: boolean;
 
   canonicalName?: string;
+
+  aliasing?: AliasingSignature | null;
+  todo_aliasing?: AliasingSignature | null;
 };
 
 /*
@@ -226,6 +241,8 @@ 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 +319,30 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       returnType: PRIMITIVE_TYPE,
       calleeEffect: Effect.Store,
       returnValueKind: ValueKind.Primitive,
+      aliasing: {
+        receiver: makeIdentifierId(0),
+        params: [],
+        rest: makeIdentifierId(1),
+        returns: makeIdentifierId(2),
+        temporaries: [],
+        effects: [
+          // Push directly mutates the array itself
+          {kind: 'Mutate', value: signatureArgument(0)},
+          // The arguments are captured into the array
+          {
+            kind: 'Capture',
+            from: signatureArgument(1),
+            into: signatureArgument(0),
+          },
+          // Returns the new length, a primitive
+          {
+            kind: 'Create',
+            into: signatureArgument(2),
+            value: ValueKind.Primitive,
+            reason: ValueReason.KnownReturnSignature,
+          },
+        ],
+      },
     }),
   ],
   [
@@ -332,6 +373,62 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
       returnValueKind: ValueKind.Mutable,
       noAlias: true,
       mutableOnlyIfOperandsAreMutable: true,
+      aliasing: {
+        receiver: makeIdentifierId(0),
+        params: [makeIdentifierId(1)],
+        rest: null,
+        returns: makeIdentifierId(2),
+        temporaries: [
+          // Temporary representing captured items of the receiver
+          signatureArgument(3),
+          // Temporary representing the result of the callback
+          signatureArgument(4),
+          /*
+           * Undefined `this` arg to the callback. Note the signature does not
+           * support passing an explicit thisArg second param
+           */
+          signatureArgument(5),
+        ],
+        effects: [
+          // Map creates a new mutable array
+          {
+            kind: 'Create',
+            into: signatureArgument(2),
+            value: ValueKind.Mutable,
+            reason: ValueReason.KnownReturnSignature,
+          },
+          // The first arg to the callback is an item extracted from the receiver array
+          {
+            kind: 'CreateFrom',
+            from: signatureArgument(0),
+            into: signatureArgument(3),
+          },
+          // The undefined this for the callback
+          {
+            kind: 'Create',
+            into: signatureArgument(5),
+            value: ValueKind.Primitive,
+            reason: ValueReason.KnownReturnSignature,
+          },
+          // calls the callback, returning the result into a temporary
+          {
+            kind: 'Apply',
+            receiver: signatureArgument(5),
+            args: [signatureArgument(3), {kind: 'Hole'}, signatureArgument(0)],
+            function: signatureArgument(1),
+            into: signatureArgument(4),
+            signature: null,
+            mutatesFunction: false,
+            loc: GeneratedSource,
+          },
+          // captures the result of the callback into the return array
+          {
+            kind: 'Capture',
+            from: signatureArgument(4),
+            into: signatureArgument(2),
+          },
+        ],
+      },
     }),
   ],
   [
@@ -479,6 +576,32 @@ addObject(BUILTIN_SHAPES, BuiltInSetId, [
       calleeEffect: Effect.Store,
       // returnValueKind is technically dependent on the ValueKind of the set itself
       returnValueKind: ValueKind.Mutable,
+      aliasing: {
+        receiver: makeIdentifierId(0),
+        params: [],
+        rest: makeIdentifierId(1),
+        returns: makeIdentifierId(2),
+        temporaries: [],
+        effects: [
+          // Set.add returns the receiver Set
+          {
+            kind: 'Assign',
+            from: signatureArgument(0),
+            into: signatureArgument(2),
+          },
+          // Set.add mutates the set itself
+          {
+            kind: 'Mutate',
+            value: signatureArgument(0),
+          },
+          // Captures the rest params into the set
+          {
+            kind: 'Capture',
+            from: signatureArgument(1),
+            into: signatureArgument(0),
+          },
+        ],
+      },
     }),
   ],
   [
@@ -948,6 +1071,19 @@ addObject(BUILTIN_SHAPES, BuiltInRefValueId, [
   ['*', {kind: 'Object', shapeId: BuiltInRefValueId}],
 ]);
 
+addFunction(
+  BUILTIN_SHAPES,
+  [],
+  {
+    positionalParams: [],
+    restParam: Effect.ConditionallyMutate,
+    returnType: {kind: 'Poly'},
+    calleeEffect: Effect.ConditionallyMutate,
+    returnValueKind: ValueKind.Mutable,
+  },
+  BuiltinEffectEventId,
+);
+
 /**
  * MixedReadOnly =
  *   | primitive
@@ -1166,6 +1302,53 @@ export const DefaultNonmutatingHook = addHook(
     calleeEffect: Effect.Read,
     hookKind: 'Custom',
     returnValueKind: ValueKind.Frozen,
+    aliasing: {
+      receiver: makeIdentifierId(0),
+      params: [],
+      rest: makeIdentifierId(1),
+      returns: makeIdentifierId(2),
+      temporaries: [],
+      effects: [
+        // Freeze the arguments
+        {
+          kind: 'Freeze',
+          value: signatureArgument(1),
+          reason: ValueReason.HookCaptured,
+        },
+        // Returns a frozen value
+        {
+          kind: 'Create',
+          into: signatureArgument(2),
+          value: ValueKind.Frozen,
+          reason: ValueReason.HookReturn,
+        },
+        // May alias any arguments into the return
+        {
+          kind: 'Alias',
+          from: signatureArgument(1),
+          into: signatureArgument(2),
+        },
+      ],
+    },
   },
   'DefaultNonmutatingHook',
 );
+
+export function signatureArgument(id: number): Place {
+  const place: Place = {
+    kind: 'Identifier',
+    effect: Effect.Unknown,
+    loc: GeneratedSource,
+    reactive: false,
+    identifier: {
+      declarationId: makeDeclarationId(id),
+      id: makeIdentifierId(id),
+      loc: GeneratedSource,
+      mutableRange: {start: makeInstructionId(0), end: makeInstructionId(0)},
+      name: null,
+      scope: null,
+      type: makeType(),
+    },
+  };
+  return place;
+}

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

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

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

@@ -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/visitors.ts

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

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

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

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

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

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

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

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

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

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

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

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

@@ -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/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

@@ -146,6 +146,7 @@ function emitLoadLoweredContextCallee(
     id: makeInstructionId(0),
     loc: GeneratedSource,
     lvalue: createTemporaryPlace(env, GeneratedSource),
+    effects: null,
     value: loadGlobal,
   };
 }
@@ -192,6 +193,7 @@ function emitPropertyLoad(
     lvalue: object,
     value: loadObj,
     id: makeInstructionId(0),
+    effects: null,
     loc: GeneratedSource,
   };
 
@@ -206,6 +208,7 @@ function emitPropertyLoad(
     lvalue: element,
     value: loadProp,
     id: makeInstructionId(0),
+    effects: null,
     loc: GeneratedSource,
   };
   return {
@@ -237,6 +240,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
       kind: 'return',
       loc: GeneratedSource,
       value: arrayInstr.lvalue,
+      effects: null,
     },
     preds: new Set(),
     phis: new Set(),
@@ -250,6 +254,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
     params: [obj],
     returnTypeAnnotation: null,
     returnType: makeType(),
+    returns: createTemporaryPlace(env, GeneratedSource),
     context: [],
     effects: null,
     body: {
@@ -278,6 +283,7 @@ function emitSelectorFn(env: Environment, keys: Array<string>): Instruction {
       loc: GeneratedSource,
     },
     lvalue: createTemporaryPlace(env, GeneratedSource),
+    effects: null,
     loc: GeneratedSource,
   };
   return fnInstr;
@@ -294,6 +300,7 @@ function emitArrayInstr(elements: Array<Place>, env: Environment): Instruction {
     id: makeInstructionId(0),
     value: array,
     lvalue: arrayLvalue,
+    effects: null,
     loc: GeneratedSource,
   };
   return arrayInstr;

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

@@ -297,6 +297,7 @@ function emitOutlinedJsx(
       },
       loc: GeneratedSource,
     },
+    effects: null,
   };
   promoteTemporaryJsxTag(loadJsx.lvalue.identifier);
   const jsxExpr: Instruction = {
@@ -312,6 +313,7 @@ function emitOutlinedJsx(
       openingLoc: GeneratedSource,
       closingLoc: GeneratedSource,
     },
+    effects: null,
   };
 
   return [loadJsx, jsxExpr];
@@ -353,6 +355,7 @@ function emitOutlinedFn(
       kind: 'return',
       loc: GeneratedSource,
       value: instructions.at(-1)!.lvalue,
+      effects: null,
     },
     preds: new Set(),
     phis: new Set(),
@@ -366,6 +369,7 @@ function emitOutlinedFn(
     params: [propsObj],
     returnTypeAnnotation: null,
     returnType: makeType(),
+    returns: createTemporaryPlace(env, GeneratedSource),
     context: [],
     effects: null,
     body: {
@@ -517,6 +521,7 @@ 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';
@@ -1310,7 +1310,7 @@ function codegenInstructionNullable(
         });
         CompilerError.invariant(value?.type === 'FunctionExpression', {
           reason: 'Expected a function as a function declaration value',
-          description: null,
+          description: `Got ${value == null ? String(value) : value.type} at ${printInstruction(instr)}`,
           loc: instr.value.loc,
           suggestions: null,
         });
@@ -1726,7 +1726,7 @@ function codegenInstructionValue(
     }
     case 'UnaryExpression': {
       value = t.unaryExpression(
-        instrValue.operator as 'throw', // todo
+        instrValue.operator,
         codegenPlaceToExpression(cx, instrValue.value),
       );
       break;
@@ -2582,7 +2582,16 @@ function codegenValue(
   value: boolean | number | string | null | undefined,
 ): t.Expression {
   if (typeof value === 'number') {
-    return t.numericLiteral(value);
+    if (value < 0) {
+      /**
+       * Babel's code generator produces invalid JS for negative numbers when
+       * run with { compact: true }.
+       * See repro https://codesandbox.io/p/devbox/5d47fr
+       */
+      return t.unaryExpression('-', t.numericLiteral(-value), false);
+    } else {
+      return t.numericLiteral(value);
+    }
   } else if (typeof value === 'boolean') {
     return t.booleanLiteral(value);
   } else if (typeof value === 'string') {

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

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

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

@@ -452,7 +452,7 @@ function visitFunctionExpression(errors: CompilerError, fn: HIRFunction): void {
                 reason:
                   'Hooks must be called at the top level in the body of a function component or custom hook, and may not be called within function expressions. See the Rules of Hooks (https://react.dev/warnings/invalid-hook-call-warning)',
                 loc: callee.loc,
-                description: `Cannot call ${hookKind} within a function component`,
+                description: `Cannot call ${hookKind === 'Custom' ? 'hook' : hookKind} within a function expression`,
                 suggestions: null,
               }),
             );

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/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/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.invalid-hoisting-setstate.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel
 import {useEffect, useState} from 'react';
 import {Stringify} from 'shared-runtime';
 
@@ -33,45 +34,17 @@ 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>
+  19 |   useEffect(() => setState(2), []);
+  20 |
+> 21 |   const [state, setState] = useState(0);
+     |                 ^^^^^^^^ InvalidReact: This variable is accessed before it is declared, which prevents the earlier access from updating when this value changes over time. Move the declaration of `setState` to before it is first referenced (21:21)
+  22 |   return <Stringify state={state} />;
+  23 | }
+  24 |
+```
+          
+      

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-return-mutable-function-from-hook.expect.md

@@ -26,7 +26,7 @@ function useFoo() {
 >  8 |     cache.set('key', 'value');
      | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 >  9 |   };
-     | ^^^^ 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 (7:9)
+     | ^^^^ 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 (7:9)
 
 InvalidReact: The function modifies a local variable here (8:8)
   10 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-uncalled-function-capturing-mutable-values-memoizes-with-captures-values.expect.md

@@ -0,0 +1,92 @@
+
+## Input
+
+```javascript
+// @flow @enableNewMutationAliasingModel
+/**
+ * This hook returns a function that when called with an input object,
+ * will return the result of mapping that input with the supplied map
+ * function. Results are cached, so if the same input is passed again,
+ * the same output object will be returned.
+ *
+ * Note that this technically violates the rules of React and is unsafe:
+ * hooks must return immutable objects and be pure, and a function which
+ * captures and mutates a value when called is inherently not pure.
+ *
+ * However, in this case it is technically safe _if_ the mapping function
+ * is pure *and* the resulting objects are never modified. This is because
+ * the function only caches: the result of `returnedFunction(someInput)`
+ * strictly depends on `returnedFunction` and `someInput`, and cannot
+ * otherwise change over time.
+ */
+hook useMemoMap<TInput: interface {}, TOutput>(
+  map: TInput => TOutput
+): TInput => TOutput {
+  return useMemo(() => {
+    // The original issue is that `cache` was not memoized together with the returned
+    // function. This was because neither appears to ever be mutated — the function
+    // is known to mutate `cache` but the function isn't called.
+    //
+    // The fix is to detect cases like this — functions that are mutable but not called -
+    // and ensure that their mutable captures are aliased together into the same scope.
+    const cache = new WeakMap<TInput, TOutput>();
+    return input => {
+      let output = cache.get(input);
+      if (output == null) {
+        output = map(input);
+        cache.set(input, output);
+      }
+      return output;
+    };
+  }, [map]);
+}
+
+```
+
+
+## Error
+
+```
+  19 |   map: TInput => TOutput
+  20 | ): TInput => TOutput {
+> 21 |   return useMemo(() => {
+     |          ^^^^^^^^^^^^^^^
+> 22 |     // The original issue is that `cache` was not memoized together with the returned
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 23 |     // function. This was because neither appears to ever be mutated — the function
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 24 |     // is known to mutate `cache` but the function isn't called.
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 25 |     //
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 26 |     // The fix is to detect cases like this — functions that are mutable but not called -
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 27 |     // and ensure that their mutable captures are aliased together into the same scope.
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 28 |     const cache = new WeakMap<TInput, TOutput>();
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 29 |     return input => {
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 30 |       let output = cache.get(input);
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 31 |       if (output == null) {
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 32 |         output = map(input);
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 33 |         cache.set(input, output);
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 34 |       }
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 35 |       return output;
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 36 |     };
+     | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+> 37 |   }, [map]);
+     | ^^^^^^^^^^^^ 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 (21:37)
+
+InvalidReact: The function modifies a local variable here (33:33)
+  38 | }
+  39 |
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-uncalled-function-capturing-mutable-values-memoizes-with-captures-values.js

@@ -1,4 +1,4 @@
-// @flow
+// @flow @enableNewMutationAliasingModel
 /**
  * This hook returns a function that when called with an input object,
  * will return the result of mapping that input with the supplied map

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.mutable-range-shared-inner-outer-function.expect.md

@@ -18,7 +18,7 @@ function Component(props) {
     a.property = true;
     b.push(false);
   };
-  return <div onClick={f()} />;
+  return <div onClick={f} />;
 }
 
 export const FIXTURE_ENTRYPOINT = {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.mutable-range-shared-inner-outer-function.js

@@ -14,7 +14,7 @@ function Component(props) {
     a.property = true;
     b.push(false);
   };
-  return <div onClick={f()} />;
+  return <div onClick={f} />;
 }
 
 export const FIXTURE_ENTRYPOINT = {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.mutate-hook-argument.expect.md

@@ -16,6 +16,8 @@ function useHook(a, b) {
   1 | function useHook(a, b) {
 > 2 |   b.test = 1;
     |   ^ InvalidReact: Mutating component props or hook arguments is not allowed. Consider using a local variable instead (2:2)
+
+InvalidReact: Mutating component props or hook arguments is not allowed. Consider using a local variable instead (3:3)
   3 |   a.test = 2;
   4 | }
   5 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.not-useEffect-external-mutate.expect.md

@@ -21,6 +21,8 @@ function Component(props) {
   4 |   foo(() => {
 > 5 |     x.a = 10;
     |     ^ InvalidReact: Writing to a variable defined outside a component or hook is not allowed. Consider using an effect (5:5)
+
+InvalidReact: Writing to a variable defined outside a component or hook is not allowed. Consider using an effect (6:6)
   6 |     x.a = 20;
   7 |   });
   8 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.object-capture-global-mutation.expect.md

@@ -2,6 +2,7 @@
 ## Input
 
 ```javascript
+// @enableNewMutationAliasingModel:false
 function Foo() {
   const x = () => {
     window.href = 'foo';
@@ -21,13 +22,13 @@ export const FIXTURE_ENTRYPOINT = {
 ## Error
 
 ```
-  1 | function Foo() {
-  2 |   const x = () => {
-> 3 |     window.href = 'foo';
-    |     ^^^^^^ InvalidReact: Writing to a variable defined outside a component or hook is not allowed. Consider using an effect (3:3)
-  4 |   };
-  5 |   const y = {x};
-  6 |   return <Bar y={y} />;
+  2 | function Foo() {
+  3 |   const x = () => {
+> 4 |     window.href = 'foo';
+    |     ^^^^^^ InvalidReact: Writing to a variable defined outside a component or hook is not allowed. Consider using an effect (4:4)
+  5 |   };
+  6 |   const y = {x};
+  7 |   return <Bar y={y} />;
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.object-capture-global-mutation.js

@@ -1,3 +1,4 @@
+// @enableNewMutationAliasingModel:false
 function Foo() {
   const x = () => {
     window.href = 'foo';

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.reassignment-to-global-indirect.expect.md

@@ -21,6 +21,8 @@ function Component() {
   3 |     // Cannot assign to globals
 > 4 |     someUnknownGlobal = 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)
+
+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) (5:5)
   5 |     moduleLocal = true;
   6 |   };
   7 |   foo();