[compiler] Simplify validation against writing refs during render

Uses a simple algorithm for detecting writes of refs during render, since the ref _read_ during render is now handled as part of ValidateNoImpureValuesInRender.

compiler/.claude/settings.local.json

@@ -1,7 +1,15 @@
 {
   "permissions": {
     "allow": [
-      "Bash(node scripts/enable-feature-flag.js:*)"
+      "Bash(node scripts/enable-feature-flag.js:*)",
+      "Bash(yarn snap:*)",
+      "Bash(for test in \"error.invalid-access-ref-during-render\" \"error.invalid-ref-in-callback-invoked-during-render\" \"error.invalid-impure-functions-in-render-via-render-helper\")",
+      "Bash(do)",
+      "Bash(echo:*)",
+      "Bash(done)",
+      "Bash(cat:*)",
+      "Bash(sl revert:*)",
+      "Bash(yarn workspace snap run build:*)"
     ],
     "deny": [],
     "ask": []

compiler/CLAUDE.md

@@ -0,0 +1,245 @@
+# React Compiler Knowledge Base
+
+This document contains knowledge about the React Compiler gathered during development sessions. It serves as a reference for understanding the codebase architecture and key concepts.
+
+## Project Structure
+
+- `packages/babel-plugin-react-compiler/` - Main compiler package
+  - `src/HIR/` - High-level Intermediate Representation types and utilities
+  - `src/Inference/` - Effect inference passes (aliasing, mutation, etc.)
+  - `src/Validation/` - Validation passes that check for errors
+  - `src/Entrypoint/Pipeline.ts` - Main compilation pipeline with pass ordering
+  - `src/__tests__/fixtures/compiler/` - Test fixtures
+    - `error.*.js` - Fixtures that should produce compilation errors
+    - `*.expect.md` - Expected output for each fixture
+
+## Running Tests
+
+```bash
+# Run all tests
+yarn snap
+
+# Run specific test by pattern
+yarn snap -p <pattern>
+
+# Update fixture outputs
+yarn snap -u
+```
+
+## Version Control
+
+This repository uses Sapling (`sl`) for version control. Unlike git, Sapling does not require explicitly adding files to the staging area.
+
+```bash
+# Check status
+sl status
+
+# Commit all changes
+sl commit -m "Your commit message"
+
+# Commit with multi-line message using heredoc
+sl commit -m "$(cat <<'EOF'
+Summary line
+
+Detailed description here
+EOF
+)"
+```
+
+## Key Concepts
+
+### HIR (High-level Intermediate Representation)
+
+The compiler converts source code to HIR for analysis. Key types in `src/HIR/HIR.ts`:
+
+- **HIRFunction** - A function being compiled
+  - `body.blocks` - Map of BasicBlocks
+  - `context` - Captured variables from outer scope
+  - `params` - Function parameters
+  - `returns` - The function's return place
+  - `aliasingEffects` - Effects that describe the function's behavior when called
+
+- **Instruction** - A single operation
+  - `lvalue` - The place being assigned to
+  - `value` - The instruction kind (CallExpression, FunctionExpression, LoadLocal, etc.)
+  - `effects` - Array of AliasingEffects for this instruction
+
+- **Terminal** - Block terminators (return, branch, etc.)
+  - `effects` - Array of AliasingEffects
+
+- **Place** - A reference to a value
+  - `identifier.id` - Unique IdentifierId
+
+- **Phi nodes** - Join points for values from different control flow paths
+  - Located at `block.phis`
+  - `phi.place` - The result place
+  - `phi.operands` - Map of predecessor block to source place
+
+### AliasingEffects System
+
+Effects describe data flow and operations. Defined in `src/Inference/AliasingEffects.ts`:
+
+**Data Flow Effects:**
+- `Impure` - Marks a place as containing an impure value (e.g., Date.now() result, ref.current)
+- `Capture a -> b` - Value from `a` is captured into `b` (mutable capture)
+- `Alias a -> b` - `b` aliases `a`
+- `ImmutableCapture a -> b` - Immutable capture (like Capture but read-only)
+- `Assign a -> b` - Direct assignment
+- `MaybeAlias a -> b` - Possible aliasing
+- `CreateFrom a -> b` - Created from source
+
+**Mutation Effects:**
+- `Mutate value` - Value is mutated
+- `MutateTransitive value` - Value and transitive captures are mutated
+- `MutateConditionally value` - May mutate
+- `MutateTransitiveConditionally value` - May mutate transitively
+
+**Other Effects:**
+- `Render place` - Place is used in render context (JSX props, component return)
+- `Freeze place` - Place is frozen (made immutable)
+- `Create place` - New value created
+- `CreateFunction` - Function expression created, includes `captures` array
+- `Apply` - Function application with receiver, function, args, and result
+
+### Hook Aliasing Signatures
+
+Located in `src/HIR/Globals.ts`, hooks can define custom aliasing signatures to control how data flows through them.
+
+**Structure:**
+```typescript
+aliasing: {
+  receiver: '@receiver',    // The hook function itself
+  params: ['@param0'],      // Named positional parameters
+  rest: '@rest',            // Rest parameters (or null)
+  returns: '@returns',      // Return value
+  temporaries: [],          // Temporary values during execution
+  effects: [                // Array of effects to apply when hook is called
+    {kind: 'Freeze', value: '@param0', reason: ValueReason.HookCaptured},
+    {kind: 'Assign', from: '@param0', into: '@returns'},
+  ],
+}
+```
+
+**Common patterns:**
+
+1. **RenderHookAliasing** (useState, useContext, useMemo, useCallback):
+   - Freezes arguments (`Freeze @rest`)
+   - Marks arguments as render-time (`Render @rest`)
+   - Creates frozen return value
+   - Aliases arguments to return
+
+2. **EffectHookAliasing** (useEffect, useLayoutEffect, useInsertionEffect):
+   - Freezes function and deps
+   - Creates internal effect object
+   - Captures function and deps into effect
+   - Returns undefined
+
+3. **Event handler hooks** (useEffectEvent):
+   - Freezes callback (`Freeze @fn`)
+   - Aliases input to return (`Assign @fn -> @returns`)
+   - NO Render effect (callback not called during render)
+
+**Example: useEffectEvent**
+```typescript
+const UseEffectEventHook = addHook(
+  DEFAULT_SHAPES,
+  {
+    positionalParams: [Effect.Freeze],  // Takes one positional param
+    restParam: null,
+    returnType: {kind: 'Function', ...},
+    calleeEffect: Effect.Read,
+    hookKind: 'useEffectEvent',
+    returnValueKind: ValueKind.Frozen,
+    aliasing: {
+      receiver: '@receiver',
+      params: ['@fn'],              // Name for the callback parameter
+      rest: null,
+      returns: '@returns',
+      temporaries: [],
+      effects: [
+        {kind: 'Freeze', value: '@fn', reason: ValueReason.HookCaptured},
+        {kind: 'Assign', from: '@fn', into: '@returns'},
+        // Note: NO Render effect - callback is not called during render
+      ],
+    },
+  },
+  BuiltInUseEffectEventId,
+);
+
+// Add as both names for compatibility
+['useEffectEvent', UseEffectEventHook],
+['experimental_useEffectEvent', UseEffectEventHook],
+```
+
+**Key insight:** If a hook is missing an `aliasing` config, it falls back to `DefaultNonmutatingHook` which includes a `Render` effect on all arguments. This can cause false positives for hooks like `useEffectEvent` whose callbacks are not called during render.
+
+### Effect Inference Pipeline
+
+Effects are populated by `InferMutationAliasingEffects` (runs before validation):
+
+1. For `Date.now()`, `Math.random()` etc. - adds `Impure` effect (controlled by `validateNoImpureFunctionsInRender` config)
+2. For `ref.current` access - adds `Impure` effect (controlled by `validateRefAccessDuringRender` config)
+3. For return terminals - adds `Alias` from return value to `fn.returns`
+4. For component/JSX returns - adds `Render` effect
+5. For function expressions - adds `CreateFunction` effect with captures
+
+### Validation: validateNoImpureValuesInRender
+
+Located at `src/Validation/ValidateNoImpureValuesInRender.ts`
+
+**Purpose:** Detect when impure values (refs, Date.now results, etc.) flow into render context.
+
+**Algorithm:**
+1. Track impure values in a Map<IdentifierId, ImpureEffect>
+2. Track functions with impure returns separately (they're not impure values themselves)
+3. Fixed-point iteration over all blocks:
+   - Process phi nodes (any impure operand makes result impure)
+   - Process instruction effects
+   - Process terminal effects
+   - Backwards propagation for mutated LoadLocal values
+4. Validate: check all Render effects against impure values
+
+**Key patterns:**
+- `Impure` effect marks the target as impure
+- `Capture/Alias/etc` propagates impurity from source to target
+- `Apply` propagates impurity from args/receiver to result
+- `CreateFunction` propagates impurity from captured values (but NOT from body effects)
+- If a value has both `Render` and `Capture` in same instruction, only error on Render (don't cascade)
+
+**Tracking functions with impure returns:**
+- Separate from the `impure` map (function values aren't impure, just their returns)
+- Populated when analyzing FunctionExpression bodies
+- Used when:
+  1. Calling the function - mark call result as impure
+  2. Capturing the function - mark target as impure (for object.foo = impureFunc cases)
+
+**Backwards propagation:**
+- When `$x = LoadLocal y` and `$x` is mutated with impure content, mark `y` as impure
+- This handles: `const arr = []; arr.push(impure); render(arr)`
+
+## Known Issues / Edge Cases
+
+### Function Outlining
+After `OutlineFunctions` pass, inner functions are replaced with `LoadGlobal(_temp)`. The validation runs BEFORE outlining, so it sees the original FunctionExpression. But be aware that test output shows post-outlining HIR.
+
+### SSA and LoadLocal
+In SSA form, each `LoadLocal` creates a new identifier. When a loaded value is mutated:
+- `$x = LoadLocal y`
+- `mutate($x, impure)`
+- `$z = LoadLocal y` (different from $x!)
+- `render($z)`
+
+The impurity in $x must propagate back to y, then forward to $z. This requires backwards propagation in the fixed-point loop.
+
+## Configuration Flags
+
+In `Environment.ts` / test directives:
+- `validateNoImpureFunctionsInRender` - Enable impure function validation (Date.now, Math.random, etc.)
+- `validateRefAccessDuringRender` - Enable ref access validation
+
+## Debugging Tips
+
+1. Run `yarn snap -p <fixture>` to see full HIR output with effects
+2. Look for `@aliasingEffects=` on FunctionExpressions
+3. Look for `Impure`, `Render`, `Capture` effects on instructions
+4. Check the pass ordering in Pipeline.ts to understand when effects are populated vs validated

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

@@ -132,6 +132,12 @@ export class CompilerDiagnostic {
     return new CompilerDiagnostic({...options, details: []});
   }
 
+  clone(): CompilerDiagnostic {
+    const cloned = CompilerDiagnostic.create({...this.options});
+    cloned.options.details = [...this.options.details];
+    return cloned;
+  }
+
   get reason(): CompilerDiagnosticOptions['reason'] {
     return this.options.reason;
   }

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

@@ -96,7 +96,6 @@ import {propagateScopeDependenciesHIR} from '../HIR/PropagateScopeDependenciesHI
 import {outlineJSX} from '../Optimization/OutlineJsx';
 import {optimizePropsMethodCalls} from '../Optimization/OptimizePropsMethodCalls';
 import {transformFire} from '../Transform';
-import {validateNoImpureFunctionsInRender} from '../Validation/ValidateNoImpureFunctionsInRender';
 import {validateStaticComponents} from '../Validation/ValidateStaticComponents';
 import {validateNoFreezingKnownMutableFunctions} from '../Validation/ValidateNoFreezingKnownMutableFunctions';
 import {inferMutationAliasingEffects} from '../Inference/InferMutationAliasingEffects';
@@ -107,6 +106,7 @@ import {nameAnonymousFunctions} from '../Transform/NameAnonymousFunctions';
 import {optimizeForSSR} from '../Optimization/OptimizeForSSR';
 import {validateExhaustiveDependencies} from '../Validation/ValidateExhaustiveDependencies';
 import {validateSourceLocations} from '../Validation/ValidateSourceLocations';
+import {validateNoImpureValuesInRender} from '../Validation/ValidateNoImpureValuesInRender';
 
 export type CompilerPipelineValue =
   | {kind: 'ast'; name: string; value: CodegenFunction}
@@ -271,10 +271,6 @@ function runWithEnvironment(
       assertValidMutableRanges(hir);
     }
 
-    if (env.config.validateRefAccessDuringRender) {
-      validateNoRefAccessInRender(hir).unwrap();
-    }
-
     if (env.config.validateNoSetStateInRender) {
       validateNoSetStateInRender(hir).unwrap();
     }
@@ -296,8 +292,15 @@ function runWithEnvironment(
       env.logErrors(validateNoJSXInTryStatement(hir));
     }
 
-    if (env.config.validateNoImpureFunctionsInRender) {
-      validateNoImpureFunctionsInRender(hir).unwrap();
+    if (
+      env.config.validateNoImpureFunctionsInRender ||
+      env.config.validateRefAccessDuringRender
+    ) {
+      validateNoImpureValuesInRender(hir).unwrap();
+    }
+
+    if (env.config.validateRefAccessDuringRender) {
+      validateNoRefAccessInRender(hir).unwrap();
     }
 
     validateNoFreezingKnownMutableFunctions(hir).unwrap();

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

@@ -38,7 +38,7 @@ import {
   addObject,
 } from './ObjectShape';
 import {BuiltInType, ObjectType, PolyType} from './Types';
-import {TypeConfig} from './TypeSchema';
+import {AliasingSignatureConfig, TypeConfig} from './TypeSchema';
 import {assertExhaustive} from '../Utils/utils';
 import {isHookName} from './Environment';
 import {CompilerError, SourceLocation} from '..';
@@ -626,11 +626,136 @@ const TYPED_GLOBALS: Array<[string, BuiltInType]> = [
   // TODO: rest of Global objects
 ];
 
+const RenderHookAliasing: (
+  reason: ValueReason,
+) => AliasingSignatureConfig = reason => ({
+  receiver: '@receiver',
+  params: [],
+  rest: '@rest',
+  returns: '@returns',
+  temporaries: [],
+  effects: [
+    // Freeze the arguments
+    {
+      kind: 'Freeze',
+      value: '@rest',
+      reason: ValueReason.HookCaptured,
+    },
+    // Render the arguments
+    {
+      kind: 'Render',
+      place: '@rest',
+    },
+    // Returns a frozen value
+    {
+      kind: 'Create',
+      into: '@returns',
+      value: ValueKind.Frozen,
+      reason,
+    },
+    // May alias any arguments into the return
+    {
+      kind: 'Alias',
+      from: '@rest',
+      into: '@returns',
+    },
+  ],
+});
+
+const EffectHookAliasing: AliasingSignatureConfig = {
+  receiver: '@receiver',
+  params: ['@fn', '@deps'],
+  rest: '@rest',
+  returns: '@returns',
+  temporaries: ['@effect'],
+  effects: [
+    // Freezes the function and deps
+    {
+      kind: 'Freeze',
+      value: '@rest',
+      reason: ValueReason.Effect,
+    },
+    {
+      kind: 'Freeze',
+      value: '@fn',
+      reason: ValueReason.Effect,
+    },
+    {
+      kind: 'Freeze',
+      value: '@deps',
+      reason: ValueReason.Effect,
+    },
+    // Deps are accessed during render
+    {
+      kind: 'Render',
+      place: '@deps',
+    },
+    // Internally creates an effect object that captures the function and deps
+    {
+      kind: 'Create',
+      into: '@effect',
+      value: ValueKind.Frozen,
+      reason: ValueReason.KnownReturnSignature,
+    },
+    // The effect stores the function and dependencies
+    {
+      kind: 'Capture',
+      from: '@rest',
+      into: '@effect',
+    },
+    {
+      kind: 'Capture',
+      from: '@fn',
+      into: '@effect',
+    },
+    // Returns undefined
+    {
+      kind: 'Create',
+      into: '@returns',
+      value: ValueKind.Primitive,
+      reason: ValueReason.KnownReturnSignature,
+    },
+  ],
+};
+
 /*
  * TODO(mofeiZ): We currently only store rest param effects for hooks.
  * now that FeatureFlag `enableTreatHooksAsFunctions` is removed we can
  * use positional params too (?)
  */
+const 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,
+    aliasing: {
+      receiver: '@receiver',
+      params: ['@value'],
+      rest: null,
+      returns: '@return',
+      temporaries: [],
+      effects: [
+        {kind: 'Assign', from: '@value', into: '@return'},
+        {
+          kind: 'Freeze',
+          value: '@value',
+          reason: ValueReason.HookCaptured,
+        },
+      ],
+    },
+  },
+  BuiltInUseEffectEventId,
+);
 const REACT_APIS: Array<[string, BuiltInType]> = [
   [
     'useContext',
@@ -644,6 +769,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         hookKind: 'useContext',
         returnValueKind: ValueKind.Frozen,
         returnValueReason: ValueReason.Context,
+        aliasing: RenderHookAliasing(ValueReason.Context),
       },
       BuiltInUseContextHookId,
     ),
@@ -658,6 +784,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       hookKind: 'useState',
       returnValueKind: ValueKind.Frozen,
       returnValueReason: ValueReason.State,
+      aliasing: RenderHookAliasing(ValueReason.State),
     }),
   ],
   [
@@ -670,6 +797,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       hookKind: 'useActionState',
       returnValueKind: ValueKind.Frozen,
       returnValueReason: ValueReason.State,
+      aliasing: RenderHookAliasing(ValueReason.HookCaptured),
     }),
   ],
   [
@@ -682,6 +810,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       hookKind: 'useReducer',
       returnValueKind: ValueKind.Frozen,
       returnValueReason: ValueReason.ReducerState,
+      aliasing: RenderHookAliasing(ValueReason.ReducerState),
     }),
   ],
   [
@@ -715,6 +844,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       calleeEffect: Effect.Read,
       hookKind: 'useMemo',
       returnValueKind: ValueKind.Frozen,
+      aliasing: RenderHookAliasing(ValueReason.HookCaptured),
     }),
   ],
   [
@@ -726,6 +856,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       calleeEffect: Effect.Read,
       hookKind: 'useCallback',
       returnValueKind: ValueKind.Frozen,
+      aliasing: RenderHookAliasing(ValueReason.HookCaptured),
     }),
   ],
   [
@@ -739,41 +870,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         calleeEffect: Effect.Read,
         hookKind: 'useEffect',
         returnValueKind: ValueKind.Frozen,
-        aliasing: {
-          receiver: '@receiver',
-          params: [],
-          rest: '@rest',
-          returns: '@returns',
-          temporaries: ['@effect'],
-          effects: [
-            // Freezes the function and deps
-            {
-              kind: 'Freeze',
-              value: '@rest',
-              reason: ValueReason.Effect,
-            },
-            // Internally creates an effect object that captures the function and deps
-            {
-              kind: 'Create',
-              into: '@effect',
-              value: ValueKind.Frozen,
-              reason: ValueReason.KnownReturnSignature,
-            },
-            // The effect stores the function and dependencies
-            {
-              kind: 'Capture',
-              from: '@rest',
-              into: '@effect',
-            },
-            // Returns undefined
-            {
-              kind: 'Create',
-              into: '@returns',
-              value: ValueKind.Primitive,
-              reason: ValueReason.KnownReturnSignature,
-            },
-          ],
-        },
+        aliasing: EffectHookAliasing,
       },
       BuiltInUseEffectHookId,
     ),
@@ -789,6 +886,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         calleeEffect: Effect.Read,
         hookKind: 'useLayoutEffect',
         returnValueKind: ValueKind.Frozen,
+        aliasing: EffectHookAliasing,
       },
       BuiltInUseLayoutEffectHookId,
     ),
@@ -804,6 +902,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         calleeEffect: Effect.Read,
         hookKind: 'useInsertionEffect',
         returnValueKind: ValueKind.Frozen,
+        aliasing: EffectHookAliasing,
       },
       BuiltInUseInsertionEffectHookId,
     ),
@@ -817,6 +916,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       calleeEffect: Effect.Read,
       hookKind: 'useTransition',
       returnValueKind: ValueKind.Frozen,
+      aliasing: RenderHookAliasing(ValueReason.HookCaptured),
     }),
   ],
   [
@@ -829,6 +929,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
       hookKind: 'useOptimistic',
       returnValueKind: ValueKind.Frozen,
       returnValueReason: ValueReason.State,
+      aliasing: RenderHookAliasing(ValueReason.HookCaptured),
     }),
   ],
   [
@@ -842,6 +943,7 @@ const REACT_APIS: Array<[string, BuiltInType]> = [
         returnType: {kind: 'Poly'},
         calleeEffect: Effect.Read,
         returnValueKind: ValueKind.Frozen,
+        aliasing: RenderHookAliasing(ValueReason.HookCaptured),
       },
       BuiltInUseOperatorId,
     ),
@@ -866,27 +968,8 @@ 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,
-    ),
-  ],
+  ['useEffectEvent', useEffectEvent],
+  ['experimental_useEffectEvent', useEffectEvent],
   ['AUTODEPS', addObject(DEFAULT_SHAPES, BuiltInAutodepsId, [])],
 ];
 

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

@@ -1879,7 +1879,15 @@ export function isRefValueType(id: Identifier): boolean {
 }
 
 export function isUseRefType(id: Identifier): boolean {
-  return id.type.kind === 'Object' && id.type.shapeId === 'BuiltInUseRefId';
+  return isUseRefType_(id.type);
+}
+
+export function isUseRefType_(type: Type): boolean {
+  return (
+    (type.kind === 'Object' && type.shapeId === 'BuiltInUseRefId') ||
+    (type.kind === 'Phi' &&
+      type.operands.some(operand => isUseRefType_(operand)))
+  );
 }
 
 export function isUseStateType(id: Identifier): boolean {
@@ -1890,6 +1898,13 @@ export function isJsxType(type: Type): boolean {
   return type.kind === 'Object' && type.shapeId === 'BuiltInJsx';
 }
 
+export function isJsxOrJsxUnionType(type: Type): boolean {
+  return (
+    (type.kind === 'Object' && type.shapeId === 'BuiltInJsx') ||
+    (type.kind === 'Phi' && type.operands.some(op => isJsxOrJsxUnionType(op)))
+  );
+}
+
 export function isRefOrRefValue(id: Identifier): boolean {
   return isUseRefType(id) || isRefValueType(id);
 }
@@ -2058,4 +2073,23 @@ export function getHookKindForType(
   return null;
 }
 
+export function areEqualSourceLocations(
+  loc1: SourceLocation,
+  loc2: SourceLocation,
+): boolean {
+  if (typeof loc1 === 'symbol' || typeof loc2 === 'symbol') {
+    return false;
+  }
+  return (
+    loc1.filename === loc2.filename &&
+    loc1.identifierName === loc2.identifierName &&
+    loc1.start.line === loc2.start.line &&
+    loc1.start.column === loc2.start.column &&
+    loc1.start.index === loc2.start.index &&
+    loc1.end.line === loc2.end.line &&
+    loc1.end.column === loc2.end.column &&
+    loc1.end.index === loc2.end.index
+  );
+}
+
 export * from './Types';

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

@@ -988,7 +988,7 @@ export function createTemporaryPlace(
     identifier: makeTemporaryIdentifier(env.nextIdentifierId, loc),
     reactive: false,
     effect: Effect.Unknown,
-    loc: GeneratedSource,
+    loc,
   };
 }
 

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

@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {CompilerError} from '../CompilerError';
+import {CompilerError, ErrorCategory} from '../CompilerError';
 import {AliasingEffect, AliasingSignature} from '../Inference/AliasingEffects';
 import {assertExhaustive} from '../Utils/utils';
 import {
@@ -190,14 +190,22 @@ function parseAliasingSignatureConfig(
           };
         }
         case 'Impure': {
-          const place = lookup(effect.place);
+          const into = lookup(effect.into);
           return {
             kind: 'Impure',
+            into,
+            category: ErrorCategory.Purity,
+            description: effect.description,
+            reason: effect.reason,
+            sourceMessage: effect.sourceMessage,
+            usageMessage: effect.usageMessage,
+          };
+        }
+        case 'Render': {
+          const place = lookup(effect.place);
+          return {
+            kind: 'Render',
             place,
-            error: CompilerError.throwTodo({
-              reason: 'Support impure effect declarations',
-              loc: GeneratedSource,
-            }),
           };
         }
         case 'Apply': {
@@ -1513,6 +1521,11 @@ export const DefaultNonmutatingHook = addHook(
           value: '@rest',
           reason: ValueReason.HookCaptured,
         },
+        // Render the arguments
+        {
+          kind: 'Render',
+          place: '@rest',
+        },
         // Returns a frozen value
         {
           kind: 'Create',

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

@@ -1009,7 +1009,7 @@ export function printAliasingEffect(effect: AliasingEffect): string {
       return `MutateGlobal ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
     }
     case 'Impure': {
-      return `Impure ${printPlaceForAliasEffect(effect.place)} reason=${JSON.stringify(effect.error.reason)}`;
+      return `Impure ${printPlaceForAliasEffect(effect.into)} reason=${effect.reason} description=${effect.description}`;
     }
     case 'Render': {
       return `Render ${printPlaceForAliasEffect(effect.place)}`;

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

@@ -185,11 +185,29 @@ export const ApplyEffectSchema: z.ZodType<ApplyEffectConfig> = z.object({
 
 export type ImpureEffectConfig = {
   kind: 'Impure';
-  place: string;
+  into: string;
+  reason: string;
+  description: string;
+  sourceMessage: string;
+  usageMessage: string;
 };
 
 export const ImpureEffectSchema: z.ZodType<ImpureEffectConfig> = z.object({
   kind: z.literal('Impure'),
+  into: LifetimeIdSchema,
+  reason: z.string(),
+  description: z.string(),
+  sourceMessage: z.string(),
+  usageMessage: z.string(),
+});
+
+export type RenderEffectConfig = {
+  kind: 'Render';
+  place: string;
+};
+
+export const RenderEffectSchema: z.ZodType<RenderEffectConfig> = z.object({
+  kind: z.literal('Render'),
   place: LifetimeIdSchema,
 });
 
@@ -204,7 +222,8 @@ export type AliasingEffectConfig =
   | ImpureEffectConfig
   | MutateEffectConfig
   | MutateTransitiveConditionallyConfig
-  | ApplyEffectConfig;
+  | ApplyEffectConfig
+  | RenderEffectConfig;
 
 export const AliasingEffectSchema: z.ZodType<AliasingEffectConfig> = z.union([
   FreezeEffectSchema,

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

@@ -5,7 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-import {CompilerDiagnostic} from '../CompilerError';
+import {CompilerDiagnostic, ErrorCategory} from '../CompilerError';
 import {
   FunctionExpression,
   GeneratedSource,
@@ -162,7 +162,15 @@ export type AliasingEffect =
   /**
    * Indicates a side-effect that is not safe during render
    */
-  | {kind: 'Impure'; place: Place; error: CompilerDiagnostic}
+  | {
+      kind: 'Impure';
+      into: Place;
+      category: ErrorCategory;
+      reason: string;
+      description: string;
+      usageMessage: string;
+      sourceMessage: string;
+    }
   /**
    * 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
@@ -222,6 +230,14 @@ export function hashEffect(effect: AliasingEffect): string {
       return [effect.kind, effect.value.identifier.id, effect.reason].join(':');
     }
     case 'Impure':
+      return [
+        effect.kind,
+        effect.into.identifier.id,
+        effect.reason,
+        effect.description,
+        effect.usageMessage,
+        effect.sourceMessage,
+      ].join(':');
     case 'Render': {
       return [effect.kind, effect.place.identifier.id].join(':');
     }

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

@@ -8,7 +8,7 @@
 import {BlockId, computePostDominatorTree, HIRFunction, Place} from '../HIR';
 import {PostDominator} from '../HIR/Dominator';
 
-export type ControlDominators = (id: BlockId) => boolean;
+export type ControlDominators = (id: BlockId) => Place | null;
 
 /**
  * Returns an object that lazily calculates whether particular blocks are controlled
@@ -23,7 +23,7 @@ export function createControlDominators(
   });
   const postDominatorFrontierCache = new Map<BlockId, Set<BlockId>>();
 
-  function isControlledBlock(id: BlockId): boolean {
+  function isControlledBlock(id: BlockId): Place | null {
     let controlBlocks = postDominatorFrontierCache.get(id);
     if (controlBlocks === undefined) {
       controlBlocks = postDominatorFrontier(fn, postDominators, id);
@@ -35,24 +35,24 @@ export function createControlDominators(
         case 'if':
         case 'branch': {
           if (isControlVariable(controlBlock.terminal.test)) {
-            return true;
+            return controlBlock.terminal.test;
           }
           break;
         }
         case 'switch': {
           if (isControlVariable(controlBlock.terminal.test)) {
-            return true;
+            return controlBlock.terminal.test;
           }
           for (const case_ of controlBlock.terminal.cases) {
             if (case_.test !== null && isControlVariable(case_.test)) {
-              return true;
+              return case_.test;
             }
           }
           break;
         }
       }
     }
-    return false;
+    return null;
   }
 
   return isControlledBlock;

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

@@ -27,11 +27,13 @@ import {
   InstructionKind,
   InstructionValue,
   isArrayType,
-  isJsxType,
+  isJsxOrJsxUnionType,
   isMapType,
+  isMutableEffect,
   isPrimitiveType,
   isRefOrRefValue,
   isSetType,
+  isUseRefType,
   makeIdentifierId,
   Phi,
   Place,
@@ -70,6 +72,7 @@ import {
   MutationReason,
 } from './AliasingEffects';
 import {ErrorCategory} from '../CompilerError';
+import {REF_ERROR_DESCRIPTION} from '../Validation/ValidateNoRefAccessInRender';
 
 const DEBUG = false;
 
@@ -569,14 +572,32 @@ function inferBlock(
       terminal.effects = effects.length !== 0 ? effects : null;
     }
   } else if (terminal.kind === 'return') {
+    terminal.effects = [
+      context.internEffect({
+        kind: 'Alias',
+        from: terminal.value,
+        into: context.fn.returns,
+      }),
+    ];
     if (!context.isFuctionExpression) {
-      terminal.effects = [
+      terminal.effects.push(
         context.internEffect({
           kind: 'Freeze',
           value: terminal.value,
           reason: ValueReason.JsxCaptured,
         }),
-      ];
+      );
+    }
+    if (
+      context.fn.fnType === 'Component' ||
+      isJsxOrJsxUnionType(context.fn.returns.identifier.type)
+    ) {
+      terminal.effects.push(
+        context.internEffect({
+          kind: 'Render',
+          place: terminal.value,
+        }),
+      );
     }
   }
 }
@@ -749,17 +770,7 @@ function applyEffect(
       break;
     }
     case 'ImmutableCapture': {
-      const kind = state.kind(effect.from).kind;
-      switch (kind) {
-        case ValueKind.Global:
-        case ValueKind.Primitive: {
-          // no-op: we don't need to track data flow for copy types
-          break;
-        }
-        default: {
-          effects.push(effect);
-        }
-      }
+      effects.push(effect);
       break;
     }
     case 'CreateFrom': {
@@ -1061,6 +1072,17 @@ function applyEffect(
             reason: new Set(fromValue.reason),
           });
           state.define(effect.into, value);
+          applyEffect(
+            context,
+            state,
+            {
+              kind: 'ImmutableCapture',
+              from: effect.from,
+              into: effect.into,
+            },
+            initialized,
+            effects,
+          );
           break;
         }
         default: {
@@ -1966,6 +1988,11 @@ function computeSignatureForInstruction(
           value: ValueKind.Primitive,
           reason: ValueReason.Other,
         });
+        effects.push({
+          kind: 'ImmutableCapture',
+          from: value.object,
+          into: lvalue,
+        });
       } else {
         effects.push({
           kind: 'CreateFrom',
@@ -1973,6 +2000,20 @@ function computeSignatureForInstruction(
           into: lvalue,
         });
       }
+      if (
+        env.config.validateRefAccessDuringRender &&
+        isUseRefType(value.object.identifier)
+      ) {
+        effects.push({
+          kind: 'Impure',
+          into: lvalue,
+          category: ErrorCategory.Refs,
+          reason: `Cannot access ref value during render`,
+          description: REF_ERROR_DESCRIPTION,
+          sourceMessage: `Ref is initially accessed`,
+          usageMessage: `Ref value is used during render`,
+        });
+      }
       break;
     }
     case 'PropertyStore':
@@ -2137,6 +2178,15 @@ function computeSignatureForInstruction(
           into: lvalue,
         });
       }
+      if (value.children != null) {
+        // Children are typically called during render, not used as an event/effect callback
+        for (const child of value.children) {
+          effects.push({
+            kind: 'Render',
+            place: child,
+          });
+        }
+      }
       if (value.kind === 'JsxExpression') {
         if (value.tag.kind === 'Identifier') {
           // Tags are render function, by definition they're called during render
@@ -2145,29 +2195,23 @@ function computeSignatureForInstruction(
             place: value.tag,
           });
         }
-        if (value.children != null) {
-          // Children are typically called during render, not used as an event/effect callback
-          for (const child of value.children) {
-            effects.push({
-              kind: 'Render',
-              place: child,
-            });
-          }
-        }
         for (const prop of value.props) {
-          if (
-            prop.kind === 'JsxAttribute' &&
-            prop.place.identifier.type.kind === 'Function' &&
-            (isJsxType(prop.place.identifier.type.return) ||
-              (prop.place.identifier.type.return.kind === 'Phi' &&
-                prop.place.identifier.type.return.operands.some(operand =>
-                  isJsxType(operand),
-                )))
-          ) {
-            // Any props which return jsx are assumed to be called during render
+          const place =
+            prop.kind === 'JsxAttribute' ? prop.place : prop.argument;
+          if (isUseRefType(place.identifier)) {
+            continue;
+          }
+          if (place.identifier.type.kind === 'Function') {
+            if (isJsxOrJsxUnionType(place.identifier.type.return)) {
+              effects.push({
+                kind: 'Render',
+                place,
+              });
+            }
+          } else {
             effects.push({
               kind: 'Render',
-              place: prop.place,
+              place,
             });
           }
         }
@@ -2203,6 +2247,11 @@ function computeSignatureForInstruction(
             value: ValueKind.Primitive,
             reason: ValueReason.Other,
           });
+          effects.push({
+            kind: 'ImmutableCapture',
+            from: value.value,
+            into: place,
+          });
         } else if (patternItem.kind === 'Identifier') {
           effects.push({
             kind: 'CreateFrom',
@@ -2384,15 +2433,46 @@ function computeSignatureForInstruction(
       });
       break;
     }
+    case 'BinaryExpression': {
+      effects.push({
+        kind: 'Create',
+        into: lvalue,
+        value: ValueKind.Primitive,
+        reason: ValueReason.Other,
+      });
+      effects.push({
+        kind: 'ImmutableCapture',
+        into: lvalue,
+        from: value.left,
+      });
+      effects.push({
+        kind: 'ImmutableCapture',
+        into: lvalue,
+        from: value.right,
+      });
+      break;
+    }
+    case 'UnaryExpression': {
+      effects.push({
+        kind: 'Create',
+        into: lvalue,
+        value: ValueKind.Primitive,
+        reason: ValueReason.Other,
+      });
+      effects.push({
+        kind: 'ImmutableCapture',
+        into: lvalue,
+        from: value.value,
+      });
+      break;
+    }
     case 'TaggedTemplateExpression':
-    case 'BinaryExpression':
     case 'Debugger':
     case 'JSXText':
     case 'MetaProperty':
     case 'Primitive':
     case 'RegExpLiteral':
     case 'TemplateLiteral':
-    case 'UnaryExpression':
     case 'UnsupportedNode': {
       effects.push({
         kind: 'Create',
@@ -2423,7 +2503,7 @@ function computeEffectsForLegacySignature(
   lvalue: Place,
   receiver: Place,
   args: Array<Place | SpreadPattern | Hole>,
-  loc: SourceLocation,
+  _loc: SourceLocation,
 ): Array<AliasingEffect> {
   const returnValueReason = signature.returnValueReason ?? ValueReason.Other;
   const effects: Array<AliasingEffect> = [];
@@ -2436,20 +2516,18 @@ function computeEffectsForLegacySignature(
   if (signature.impure && state.env.config.validateNoImpureFunctionsInRender) {
     effects.push({
       kind: 'Impure',
-      place: receiver,
-      error: CompilerDiagnostic.create({
-        category: ErrorCategory.Purity,
-        reason: 'Cannot call impure function during render',
-        description:
-          (signature.canonicalName != null
-            ? `\`${signature.canonicalName}\` is an impure function. `
-            : '') +
-          'Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent)',
-      }).withDetails({
-        kind: 'error',
-        loc,
-        message: 'Cannot call impure function',
-      }),
+      into: lvalue,
+      category: ErrorCategory.Purity,
+      reason: 'Cannot access impure value during render',
+      description:
+        'Calling an impure function can produce unstable results that update ' +
+        'unpredictably when the component happens to re-render. ' +
+        '(https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent)',
+      sourceMessage:
+        signature.canonicalName != null
+          ? `\`${signature.canonicalName}\` is an impure function.`
+          : 'This function is impure',
+      usageMessage: 'Cannot access impure value during render',
     });
   }
   if (signature.knownIncompatible != null && state.env.enableValidations) {
@@ -2748,7 +2826,23 @@ function computeEffectsForSignature(
         }
         break;
       }
-      case 'Impure':
+      case 'Impure': {
+        if (env.config.validateNoImpureFunctionsInRender) {
+          const values = substitutions.get(effect.into.identifier.id) ?? [];
+          for (const value of values) {
+            effects.push({
+              kind: effect.kind,
+              into: value,
+              category: effect.category,
+              reason: effect.reason,
+              description: effect.description,
+              sourceMessage: effect.sourceMessage,
+              usageMessage: effect.usageMessage,
+            });
+          }
+        }
+        break;
+      }
       case 'MutateFrozen':
       case 'MutateGlobal': {
         const values = substitutions.get(effect.place.identifier.id) ?? [];

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

@@ -19,6 +19,7 @@ import {
   ValueReason,
   Place,
   isPrimitiveType,
+  isUseRefType,
 } from '../HIR/HIR';
 import {
   eachInstructionLValue,
@@ -28,6 +29,9 @@ import {
 import {assertExhaustive, getOrInsertWith} from '../Utils/utils';
 import {Err, Ok, Result} from '../Utils/Result';
 import {AliasingEffect, MutationReason} from './AliasingEffects';
+import {printIdentifier, printType} from '../HIR/PrintHIR';
+
+const DEBUG = false;
 
 /**
  * This pass builds an abstract model of the heap and interprets the effects of the
@@ -104,7 +108,6 @@ export function inferMutationAliasingRanges(
     reason: MutationReason | null;
   }> = [];
   const renders: Array<{index: number; place: Place}> = [];
-
   let index = 0;
 
   const errors = new CompilerError();
@@ -197,14 +200,12 @@ export function inferMutationAliasingRanges(
           });
         } else if (
           effect.kind === 'MutateFrozen' ||
-          effect.kind === 'MutateGlobal' ||
-          effect.kind === 'Impure'
+          effect.kind === 'MutateGlobal'
         ) {
           errors.pushDiagnostic(effect.error);
           functionEffects.push(effect);
         } else if (effect.kind === 'Render') {
           renders.push({index: index++, place: effect.place});
-          functionEffects.push(effect);
         }
       }
     }
@@ -214,10 +215,6 @@ export function inferMutationAliasingRanges(
         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') &&
@@ -227,23 +224,31 @@ export function inferMutationAliasingRanges(
         if (effect.kind === 'Alias') {
           state.assign(index++, effect.from, effect.into);
         } else {
-          CompilerError.invariant(effect.kind === 'Freeze', {
-            reason: `Unexpected '${effect.kind}' effect for MaybeThrow terminal`,
-            description: null,
-            details: [
-              {
-                kind: 'error',
-                loc: block.terminal.loc,
-                message: null,
-              },
-            ],
-          });
+          CompilerError.invariant(
+            effect.kind === 'Freeze' || effect.kind === 'Render',
+            {
+              reason: `Unexpected '${effect.kind}' effect for MaybeThrow terminal`,
+              description: null,
+              details: [
+                {
+                  kind: 'error',
+                  loc: block.terminal.loc,
+                  message: null,
+                },
+              ],
+            },
+          );
         }
       }
     }
   }
 
   for (const mutation of mutations) {
+    if (DEBUG) {
+      console.log(
+        `[${mutation.index}] mutate ${printIdentifier(mutation.place.identifier)}`,
+      );
+    }
     state.mutate(
       mutation.index,
       mutation.place.identifier,
@@ -255,8 +260,16 @@ export function inferMutationAliasingRanges(
       errors,
     );
   }
+  if (DEBUG) {
+    console.log(state.debug());
+  }
   for (const render of renders) {
-    state.render(render.index, render.place.identifier, errors);
+    if (DEBUG) {
+      console.log(
+        `[${render.index}] render ${printIdentifier(render.place.identifier)}`,
+      );
+    }
+    state.render(render.index, render.place, errors);
   }
   for (const param of [...fn.context, ...fn.params]) {
     const place = param.kind === 'Identifier' ? param : param.place;
@@ -515,6 +528,13 @@ export function inferMutationAliasingRanges(
   const ignoredErrors = new CompilerError();
   for (const param of [...fn.params, ...fn.context, fn.returns]) {
     const place = param.kind === 'Identifier' ? param : param.place;
+    const node = state.nodes.get(place.identifier);
+    if (node != null && node.render != null) {
+      functionEffects.push({
+        kind: 'Render',
+        place: place,
+      });
+    }
     tracked.push(place);
   }
   for (const into of tracked) {
@@ -577,7 +597,6 @@ export function inferMutationAliasingRanges(
 function appendFunctionErrors(errors: CompilerError, fn: HIRFunction): void {
   for (const effect of fn.aliasingEffects ?? []) {
     switch (effect.kind) {
-      case 'Impure':
       case 'MutateFrozen':
       case 'MutateGlobal': {
         errors.pushDiagnostic(effect.error);
@@ -612,10 +631,74 @@ type Node = {
     | {kind: 'Object'}
     | {kind: 'Phi'}
     | {kind: 'Function'; function: HIRFunction};
+  render: Place | null;
 };
+
+function _printNode(node: Node): string {
+  const out: Array<string> = [];
+  debugNode(out, node);
+  return out.join('\n');
+}
+function debugNode(out: Array<string>, node: Node): void {
+  out.push(
+    printIdentifier(node.id) +
+      printType(node.id.type) +
+      ` lastMutated=[${node.lastMutated}]`,
+  );
+  if (node.transitive != null) {
+    out.push(`  transitive=${node.transitive.kind}`);
+  }
+  if (node.local != null) {
+    out.push(`  local=${node.local.kind}`);
+  }
+  if (node.mutationReason != null) {
+    out.push(`  mutationReason=${node.mutationReason?.kind}`);
+  }
+  const edges: Array<{
+    index: number;
+    direction: '<=' | '=>';
+    kind: string;
+    id: Identifier;
+  }> = [];
+  for (const [alias, index] of node.createdFrom) {
+    edges.push({index, direction: '<=', kind: 'createFrom', id: alias});
+  }
+  for (const [alias, index] of node.aliases) {
+    edges.push({index, direction: '<=', kind: 'alias', id: alias});
+  }
+  for (const [alias, index] of node.maybeAliases) {
+    edges.push({index, direction: '<=', kind: 'alias?', id: alias});
+  }
+  for (const [alias, index] of node.captures) {
+    edges.push({index, direction: '<=', kind: 'capture', id: alias});
+  }
+  for (const edge of node.edges) {
+    edges.push({
+      index: edge.index,
+      direction: '=>',
+      kind: edge.kind,
+      id: edge.node,
+    });
+  }
+  edges.sort((a, b) => a.index - b.index);
+  for (const edge of edges) {
+    out.push(
+      `  [${edge.index}] ${edge.direction} ${edge.kind} ${printIdentifier(edge.id)}`,
+    );
+  }
+}
+
 class AliasingState {
   nodes: Map<Identifier, Node> = new Map();
 
+  debug(): string {
+    const items: Array<string> = [];
+    for (const [_id, node] of this.nodes) {
+      debugNode(items, node);
+    }
+    return items.join('\n');
+  }
+
   create(place: Place, value: Node['value']): void {
     this.nodes.set(place.identifier, {
       id: place.identifier,
@@ -629,6 +712,7 @@ class AliasingState {
       lastMutated: 0,
       mutationReason: null,
       value,
+      render: null,
     });
   }
 
@@ -681,9 +765,9 @@ class AliasingState {
     }
   }
 
-  render(index: number, start: Identifier, errors: CompilerError): void {
+  render(index: number, start: Place, errors: CompilerError): void {
     const seen = new Set<Identifier>();
-    const queue: Array<Identifier> = [start];
+    const queue: Array<Identifier> = [start.identifier];
     while (queue.length !== 0) {
       const current = queue.pop()!;
       if (seen.has(current)) {
@@ -691,11 +775,34 @@ class AliasingState {
       }
       seen.add(current);
       const node = this.nodes.get(current);
-      if (node == null || node.transitive != null || node.local != null) {
+      if (node == null || isUseRefType(node.id)) {
+        if (DEBUG) {
+          console.log(`  render ${printIdentifier(current)}: skip mutated/ref`);
+        }
         continue;
       }
-      if (node.value.kind === 'Function') {
-        appendFunctionErrors(errors, node.value.function);
+      if (
+        node.local == null &&
+        node.transitive == null &&
+        node.value.kind === 'Function'
+      ) {
+        const returns = node.value.function.returns;
+        if (
+          isJsxType(returns.identifier.type) ||
+          (returns.identifier.type.kind === 'Phi' &&
+            returns.identifier.type.operands.some(operand =>
+              isJsxType(operand),
+            ))
+        ) {
+          appendFunctionErrors(errors, node.value.function);
+        }
+        if (DEBUG) {
+          console.log(`  render ${printIdentifier(current)}: skip function`);
+        }
+        continue;
+      }
+      if (node.render == null) {
+        node.render = start;
       }
       for (const [alias, when] of node.createdFrom) {
         if (when >= index) {
@@ -709,6 +816,12 @@ class AliasingState {
         }
         queue.push(alias);
       }
+      for (const [alias, when] of node.maybeAliases) {
+        if (when >= index) {
+          continue;
+        }
+        queue.push(alias);
+      }
       for (const [capture, when] of node.captures) {
         if (when >= index) {
           continue;

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

@@ -167,6 +167,14 @@ export function Set_filter<T>(
   return result;
 }
 
+export function Set_subtract<T>(
+  source: ReadonlySet<T>,
+  other: Iterable<T>,
+): Set<T> {
+  const otherSet = other instanceof Set ? other : new Set(other);
+  return Set_filter(source, item => !otherSet.has(item));
+}
+
 export function hasNode<T>(
   input: NodePath<T | null | undefined>,
 ): input is NodePath<NonNullable<T>> {

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

@@ -1,59 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-import {CompilerDiagnostic, CompilerError} from '..';
-import {ErrorCategory} from '../CompilerError';
-import {HIRFunction} from '../HIR';
-import {getFunctionCallSignature} from '../Inference/InferMutationAliasingEffects';
-import {Result} from '../Utils/Result';
-
-/**
- * Checks that known-impure functions are not called during render. Examples of invalid functions to
- * call during render are `Math.random()` and `Date.now()`. Users may extend this set of
- * impure functions via a module type provider and specifying functions with `impure: true`.
- *
- * TODO: add best-effort analysis of functions which are called during render. We have variations of
- * this in several of our validation passes and should unify those analyses into a reusable helper
- * and use it here.
- */
-export function validateNoImpureFunctionsInRender(
-  fn: HIRFunction,
-): Result<void, CompilerError> {
-  const errors = new CompilerError();
-  for (const [, block] of fn.body.blocks) {
-    for (const instr of block.instructions) {
-      const value = instr.value;
-      if (value.kind === 'MethodCall' || value.kind == 'CallExpression') {
-        const callee =
-          value.kind === 'MethodCall' ? value.property : value.callee;
-        const signature = getFunctionCallSignature(
-          fn.env,
-          callee.identifier.type,
-        );
-        if (signature != null && signature.impure === true) {
-          errors.pushDiagnostic(
-            CompilerDiagnostic.create({
-              category: ErrorCategory.Purity,
-              reason: 'Cannot call impure function during render',
-              description:
-                (signature.canonicalName != null
-                  ? `\`${signature.canonicalName}\` is an impure function. `
-                  : '') +
-                'Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent)',
-              suggestions: null,
-            }).withDetails({
-              kind: 'error',
-              loc: callee.loc,
-              message: 'Cannot call impure function',
-            }),
-          );
-        }
-      }
-    }
-  }
-  return errors.asResult();
-}

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

@@ -0,0 +1,307 @@
+/**
+ * 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 {CompilerDiagnostic, CompilerError, Effect} from '..';
+import {
+  areEqualSourceLocations,
+  HIRFunction,
+  IdentifierId,
+  InstructionId,
+  isJsxType,
+  isRefValueType,
+  isUseRefType,
+} from '../HIR';
+import {
+  eachInstructionLValue,
+  eachInstructionValueOperand,
+} from '../HIR/visitors';
+import {AliasingEffect} from '../Inference/AliasingEffects';
+import {createControlDominators} from '../Inference/ControlDominators';
+import {isMutable} from '../ReactiveScopes/InferReactiveScopeVariables';
+import {Err, Ok, Result} from '../Utils/Result';
+import {
+  assertExhaustive,
+  getOrInsertWith,
+  Set_filter,
+  Set_subtract,
+} from '../Utils/utils';
+import {printInstruction} from '../HIR/PrintHIR';
+
+type ImpureEffect = Extract<AliasingEffect, {kind: 'Impure'}>;
+type RenderEffect = Extract<AliasingEffect, {kind: 'Render'}>;
+type FunctionCache = Map<HIRFunction, Map<string, ImpuritySignature>>;
+type ImpuritySignature = {effects: Array<ImpureEffect>; error: CompilerError};
+
+export function validateNoImpureValuesInRender(
+  fn: HIRFunction,
+): Result<void, CompilerError> {
+  const impure = new Map<IdentifierId, ImpureEffect>();
+  const result = inferImpureValues(fn, impure, new Map());
+
+  if (result.error.hasAnyErrors()) {
+    return Err(result.error);
+  }
+  return Ok(undefined);
+}
+
+function inferFunctionExpressionMemo(
+  fn: HIRFunction,
+  impure: Map<IdentifierId, ImpureEffect>,
+  cache: FunctionCache,
+): ImpuritySignature {
+  const key = fn.context
+    .map(place => `${place.identifier.id}:${impure.has(place.identifier.id)}`)
+    .join(',');
+  return getOrInsertWith(
+    getOrInsertWith(cache, fn, () => new Map()),
+    key,
+    () => inferImpureValues(fn, impure, cache),
+  );
+}
+
+function processEffects(
+  id: InstructionId,
+  effects: Array<AliasingEffect>,
+  impure: Map<IdentifierId, ImpureEffect>,
+  cache: FunctionCache,
+): boolean {
+  let hasChanges = false;
+  const rendered: Set<IdentifierId> = new Set();
+  for (const effect of effects) {
+    if (effect.kind === 'Render') {
+      rendered.add(effect.place.identifier.id);
+    }
+  }
+  for (const effect of effects) {
+    switch (effect.kind) {
+      case 'Alias':
+      case 'Assign':
+      case 'Capture':
+      case 'CreateFrom':
+      case 'ImmutableCapture': {
+        const sourceEffect = impure.get(effect.from.identifier.id);
+        if (
+          sourceEffect != null &&
+          !impure.has(effect.into.identifier.id) &&
+          !rendered.has(effect.from.identifier.id) &&
+          !isUseRefType(effect.into.identifier) &&
+          !isJsxType(effect.into.identifier.type)
+        ) {
+          impure.set(effect.into.identifier.id, sourceEffect);
+          hasChanges = true;
+        }
+        if (
+          sourceEffect == null &&
+          (effect.kind === 'Assign' || effect.kind === 'Capture') &&
+          !impure.has(effect.from.identifier.id) &&
+          !rendered.has(effect.from.identifier.id) &&
+          !isUseRefType(effect.from.identifier) &&
+          isMutable({id}, effect.into)
+        ) {
+          const destinationEffect = impure.get(effect.into.identifier.id);
+          if (destinationEffect != null) {
+            impure.set(effect.from.identifier.id, destinationEffect);
+            hasChanges = true;
+          }
+        }
+        break;
+      }
+      case 'Impure': {
+        if (!impure.has(effect.into.identifier.id)) {
+          impure.set(effect.into.identifier.id, effect);
+          hasChanges = true;
+        }
+        break;
+      }
+      case 'Render': {
+        break;
+      }
+      case 'CreateFunction': {
+        const result = inferFunctionExpressionMemo(
+          effect.function.loweredFunc.func,
+          impure,
+          cache,
+        );
+        if (result.error.hasAnyErrors()) {
+          break;
+        }
+        const impureEffect: ImpureEffect | null =
+          result.effects.find(
+            (functionEffect: AliasingEffect): functionEffect is ImpureEffect =>
+              functionEffect.kind === 'Impure' &&
+              functionEffect.into.identifier.id ===
+                effect.function.loweredFunc.func.returns.identifier.id,
+          ) ?? null;
+        if (impureEffect != null) {
+          impure.set(effect.into.identifier.id, impureEffect);
+          hasChanges = true;
+        }
+        break;
+      }
+      case 'MaybeAlias':
+      case 'Apply':
+      case 'Create':
+      case 'Freeze':
+      case 'Mutate':
+      case 'MutateConditionally':
+      case 'MutateFrozen':
+      case 'MutateGlobal':
+      case 'MutateTransitive':
+      case 'MutateTransitiveConditionally': {
+        break;
+      }
+    }
+  }
+  return hasChanges;
+}
+
+function inferImpureValues(
+  fn: HIRFunction,
+  impure: Map<IdentifierId, ImpureEffect>,
+  cache: FunctionCache,
+): ImpuritySignature {
+  const getBlockControl = createControlDominators(fn, place => {
+    return impure.has(place.identifier.id);
+  });
+
+  let hasChanges = false;
+  do {
+    hasChanges = false;
+
+    for (const block of fn.body.blocks.values()) {
+      const controlPlace = getBlockControl(block.id);
+      const controlImpureEffect =
+        controlPlace != null ? impure.get(controlPlace.identifier.id) : null;
+
+      for (const phi of block.phis) {
+        if (impure.has(phi.place.identifier.id)) {
+          // Already marked impure on a previous pass
+          continue;
+        }
+        let impureEffect = null;
+        for (const [, operand] of phi.operands) {
+          const operandEffect = impure.get(operand.identifier.id);
+          if (operandEffect != null) {
+            impureEffect = operandEffect;
+            break;
+          }
+        }
+        if (impureEffect != null) {
+          impure.set(phi.place.identifier.id, impureEffect);
+          hasChanges = true;
+        } else {
+          for (const [pred] of phi.operands) {
+            const predControl = getBlockControl(pred);
+            if (predControl != null) {
+              const predEffect = impure.get(predControl.identifier.id);
+              if (predEffect != null) {
+                impure.set(phi.place.identifier.id, predEffect);
+                hasChanges = true;
+                break;
+              }
+            }
+          }
+        }
+      }
+
+      for (const instr of block.instructions) {
+        const _impure = new Set(impure.keys());
+        hasChanges =
+          processEffects(instr.id, instr.effects ?? [], impure, cache) ||
+          hasChanges;
+      }
+      if (block.terminal.kind === 'return' && block.terminal.effects != null) {
+        hasChanges =
+          processEffects(
+            block.terminal.id,
+            block.terminal.effects,
+            impure,
+            cache,
+          ) || hasChanges;
+      }
+    }
+  } while (hasChanges);
+
+  fn.env.logger?.debugLogIRs?.({
+    kind: 'debug',
+    name: 'ValidateNoImpureValuesInRender',
+    value: JSON.stringify(Array.from(impure.keys()).sort(), null, 2),
+  });
+
+  const error = new CompilerError();
+  function validateRenderEffect(effect: RenderEffect): void {
+    const impureEffect = impure.get(effect.place.identifier.id);
+    if (impureEffect == null) {
+      return;
+    }
+    const diagnostic = CompilerDiagnostic.create({
+      category: impureEffect.category,
+      reason: impureEffect.reason,
+      description: impureEffect.description,
+    }).withDetails({
+      kind: 'error',
+      loc: effect.place.loc,
+      message: impureEffect.usageMessage,
+    });
+    if (!areEqualSourceLocations(effect.place.loc, impureEffect.into.loc)) {
+      diagnostic.withDetails({
+        kind: 'error',
+        loc: impureEffect.into.loc,
+        message: impureEffect.sourceMessage,
+      });
+    }
+    error.pushDiagnostic(diagnostic);
+  }
+  for (const block of fn.body.blocks.values()) {
+    for (const instr of block.instructions) {
+      const value = instr.value;
+      if (
+        value.kind === 'FunctionExpression' ||
+        value.kind === 'ObjectMethod'
+      ) {
+        const result = inferFunctionExpressionMemo(
+          value.loweredFunc.func,
+          impure,
+          cache,
+        );
+        if (result.error.hasAnyErrors()) {
+          error.merge(result.error);
+        }
+      }
+      for (const effect of instr.effects ?? []) {
+        if (effect.kind === 'Render') {
+          validateRenderEffect(effect);
+        }
+      }
+    }
+    if (block.terminal.kind === 'return' && block.terminal.effects != null) {
+      for (const effect of block.terminal.effects) {
+        if (effect.kind === 'Render') {
+          validateRenderEffect(effect);
+        }
+      }
+    }
+  }
+  const impureEffects: Array<ImpureEffect> = [];
+  for (const param of [...fn.context, ...fn.params, fn.returns]) {
+    const place = param.kind === 'Identifier' ? param : param.place;
+    const impureEffect = impure.get(place.identifier.id);
+    if (impureEffect != null) {
+      impureEffects.push({
+        kind: 'Impure',
+        into: impureEffect.into,
+        category: impureEffect.category,
+        reason: impureEffect.reason,
+        description: impureEffect.description,
+        sourceMessage: impureEffect.sourceMessage,
+        usageMessage: impureEffect.usageMessage,
+      });
+    }
+  }
+  return {effects: impureEffects, error};
+}

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

@@ -202,10 +202,10 @@ function getSetStateCall(
     );
   };
 
-  const isRefControlledBlock: (id: BlockId) => boolean =
+  const isRefControlledBlock: (id: BlockId) => Place | null =
     enableAllowSetStateFromRefsInEffects
       ? createControlDominators(fn, place => isDerivedFromRef(place))
-      : (): boolean => false;
+      : (): Place | null => null;
 
   for (const [, block] of fn.body.blocks) {
     if (enableAllowSetStateFromRefsInEffects) {
@@ -224,7 +224,7 @@ function getSetStateCall(
           refDerivedValues.add(phi.place.identifier.id);
         } else {
           for (const [pred] of phi.operands) {
-            if (isRefControlledBlock(pred)) {
+            if (isRefControlledBlock(pred) != null) {
               refDerivedValues.add(phi.place.identifier.id);
               break;
             }
@@ -337,7 +337,7 @@ function getSetStateCall(
                  * be needed when initial layout measurements from refs need to be stored in state.
                  */
                 return null;
-              } else if (isRefControlledBlock(block.id)) {
+              } else if (isRefControlledBlock(block.id) != null) {
                 continue;
               }
             }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/access-ref-in-render-mutate-object-with-ref-function.expect.md

@@ -0,0 +1,51 @@
+
+## Input
+
+```javascript
+import {useRef} from 'react';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
+function Component() {
+  const ref = useRef(null);
+  const object = {};
+  object.foo = () => ref.current;
+  const refValue = object.foo();
+  return <div>{refValue}</div>;
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { useRef } from "react";
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
+function Component() {
+  const $ = _c(2);
+  const ref = useRef(null);
+  const object = {};
+  object.foo = () => ref.current;
+  const refValue = object.foo();
+  let t0;
+  if ($[0] !== refValue) {
+    t0 = <div>{refValue}</div>;
+    $[0] = refValue;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  return t0;
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/access-ref-in-render-mutate-object-with-ref-function.js

@@ -1,5 +1,9 @@
 import {useRef} from 'react';
 
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
 function Component() {
   const ref = useRef(null);
   const object = {};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capture-ref-for-mutation.expect.md

@@ -0,0 +1,74 @@
+
+## Input
+
+```javascript
+import {useRef} from 'react';
+import {addOne} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
+function useKeyCommand() {
+  const currentPosition = useRef(0);
+  const handleKey = direction => () => {
+    const position = currentPosition.current;
+    const nextPosition = direction === 'left' ? addOne(position) : position;
+    currentPosition.current = nextPosition;
+  };
+  const moveLeft = {
+    handler: handleKey('left')(),
+  };
+  const moveRight = {
+    handler: handleKey('right')(),
+  };
+  return [moveLeft, moveRight];
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useKeyCommand,
+  params: [],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { useRef } from "react";
+import { addOne } from "shared-runtime";
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
+function useKeyCommand() {
+  const $ = _c(1);
+  const currentPosition = useRef(0);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    const handleKey = (direction) => () => {
+      const position = currentPosition.current;
+      const nextPosition = direction === "left" ? addOne(position) : position;
+      currentPosition.current = nextPosition;
+    };
+    const moveLeft = { handler: handleKey("left")() };
+    const moveRight = { handler: handleKey("right")() };
+    t0 = [moveLeft, moveRight];
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useKeyCommand,
+  params: [],
+};
+
+```
+      
+### Eval output
+(kind: ok) [{},{}]

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capture-ref-for-mutation.tsx

@@ -1,6 +1,10 @@
 import {useRef} from 'react';
 import {addOne} from 'shared-runtime';
 
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
 function useKeyCommand() {
   const currentPosition = useRef(0);
   const handleKey = direction => () => {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capturing-ref-returning-function-in-rendered-object.expect.md

@@ -5,6 +5,10 @@
 import {useRef} from 'react';
 import {Stringify} from 'shared-runtime';
 
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
 function Component(props) {
   const ref = useRef(props.value);
   const object = {};
@@ -26,6 +30,10 @@ import { c as _c } from "react/compiler-runtime";
 import { useRef } from "react";
 import { Stringify } from "shared-runtime";
 
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
 function Component(props) {
   const $ = _c(1);
   const ref = useRef(props.value);

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/capturing-ref-returning-function-in-rendered-object.js

@@ -1,6 +1,10 @@
 import {useRef} from 'react';
 import {Stringify} from 'shared-runtime';
 
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
 function Component(props) {
   const ref = useRef(props.value);
   const object = {};

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.expect.md

@@ -5,6 +5,7 @@
 function Component() {
   const Foo = () => {
     someGlobal = true;
+    return <div />;
   };
   return <Foo />;
 }
@@ -26,9 +27,9 @@ error.assign-global-in-component-tag-function.ts:3:4
   2 |   const Foo = () => {
 > 3 |     someGlobal = true;
     |     ^^^^^^^^^^ `someGlobal` cannot be reassigned
-  4 |   };
-  5 |   return <Foo />;
-  6 | }
+  4 |     return <div />;
+  5 |   };
+  6 |   return <Foo />;
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.assign-global-in-component-tag-function.js

@@ -1,6 +1,7 @@
 function Component() {
   const Foo = () => {
     someGlobal = true;
+    return <div />;
   };
   return <Foo />;
 }

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

@@ -5,6 +5,7 @@
 function Component() {
   const foo = () => {
     someGlobal = true;
+    return <div />;
   };
   // Children are generally access/called during render, so
   // modifying a global in a children function is almost
@@ -29,9 +30,9 @@ error.assign-global-in-jsx-children.ts:3:4
   2 |   const foo = () => {
 > 3 |     someGlobal = true;
     |     ^^^^^^^^^^ `someGlobal` cannot be reassigned
-  4 |   };
-  5 |   // Children are generally access/called during render, so
-  6 |   // modifying a global in a children function is almost
+  4 |     return <div />;
+  5 |   };
+  6 |   // Children are generally access/called during render, so
 ```
           
       

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

@@ -1,6 +1,7 @@
 function Component() {
   const foo = () => {
     someGlobal = true;
+    return <div />;
   };
   // Children are generally access/called during render, so
   // modifying a global in a children function is almost

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

@@ -1,64 +0,0 @@
-
-## Input
-
-```javascript
-import {useRef} from 'react';
-import {addOne} from 'shared-runtime';
-
-function useKeyCommand() {
-  const currentPosition = useRef(0);
-  const handleKey = direction => () => {
-    const position = currentPosition.current;
-    const nextPosition = direction === 'left' ? addOne(position) : position;
-    currentPosition.current = nextPosition;
-  };
-  const moveLeft = {
-    handler: handleKey('left')(),
-  };
-  const moveRight = {
-    handler: handleKey('right')(),
-  };
-  return [moveLeft, moveRight];
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useKeyCommand,
-  params: [],
-};
-
-```
-
-
-## Error
-
-```
-Found 2 errors:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.capture-ref-for-mutation.ts:12:13
-  10 |   };
-  11 |   const moveLeft = {
-> 12 |     handler: handleKey('left')(),
-     |              ^^^^^^^^^^^^^^^^^ This function accesses a ref value
-  13 |   };
-  14 |   const moveRight = {
-  15 |     handler: handleKey('right')(),
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.capture-ref-for-mutation.ts:15:13
-  13 |   };
-  14 |   const moveRight = {
-> 15 |     handler: handleKey('right')(),
-     |              ^^^^^^^^^^^^^^^^^^ This function accesses a ref value
-  16 |   };
-  17 |   return [moveLeft, moveRight];
-  18 | }
-```
-          
-      

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

@@ -20,30 +20,26 @@ export const FIXTURE_ENTRYPOINT = {
 ## Error
 
 ```
-Found 2 errors:
+Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-error.hook-ref-value.ts:5:23
+error.hook-ref-value.ts:5:22
   3 | function Component(props) {
   4 |   const ref = useRef();
 > 5 |   useEffect(() => {}, [ref.current]);
-    |                        ^^^^^^^^^^^ Cannot access ref value during render
+    |                       ^^^^^^^^^^^^^ Ref value is used during render
   6 | }
   7 |
   8 | export const FIXTURE_ENTRYPOINT = {
 
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
 error.hook-ref-value.ts:5:23
   3 | function Component(props) {
   4 |   const ref = useRef();
 > 5 |   useEffect(() => {}, [ref.current]);
-    |                        ^^^^^^^^^^^ Cannot access ref value during render
+    |                        ^^^^^^^^^^^ Ref is initially accessed
   6 | }
   7 |
   8 | export const FIXTURE_ENTRYPOINT = {

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

@@ -17,15 +17,23 @@ function Component(props) {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
+error.invalid-access-ref-during-render.ts:5:9
+  3 |   const ref = useRef(null);
+  4 |   const value = ref.current;
+> 5 |   return value;
+    |          ^^^^^ Ref value is used during render
+  6 | }
+  7 |
+
 error.invalid-access-ref-during-render.ts:4:16
   2 | function Component(props) {
   3 |   const ref = useRef(null);
 > 4 |   const value = ref.current;
-    |                 ^^^^^^^^^^^ Cannot access ref value during render
+    |                 ^^^^^^^^^^^ Ref is initially accessed
   5 |   return value;
   6 | }
   7 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-access-ref-in-reducer-init.expect.md

@@ -28,7 +28,7 @@ export const FIXTURE_ENTRYPOINT = {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -36,7 +36,16 @@ error.invalid-access-ref-in-reducer-init.ts:8:4
    6 |     (state, action) => state + action,
    7 |     0,
 >  8 |     init => ref.current
-     |     ^^^^^^^^^^^^^^^^^^^ Passing a ref to a function may read its value during render
+     |     ^^^^^^^^^^^^^^^^^^^ Ref value is used during render
+   9 |   );
+  10 |
+  11 |   return <Stringify state={state} />;
+
+error.invalid-access-ref-in-reducer-init.ts:8:12
+   6 |     (state, action) => state + action,
+   7 |     0,
+>  8 |     init => ref.current
+     |             ^^^^^^^^^^^ Ref is initially accessed
    9 |   );
   10 |
   11 |   return <Stringify state={state} />;

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

@@ -24,7 +24,7 @@ export const FIXTURE_ENTRYPOINT = {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -32,7 +32,16 @@ error.invalid-access-ref-in-reducer.ts:5:29
   3 | function Component(props) {
   4 |   const ref = useRef(props.value);
 > 5 |   const [state] = useReducer(() => ref.current, null);
-    |                              ^^^^^^^^^^^^^^^^^ Passing a ref to a function may read its value during render
+    |                              ^^^^^^^^^^^^^^^^^ Ref value is used during render
+  6 |
+  7 |   return <Stringify state={state} />;
+  8 | }
+
+error.invalid-access-ref-in-reducer.ts:5:35
+  3 | function Component(props) {
+  4 |   const ref = useRef(props.value);
+> 5 |   const [state] = useReducer(() => ref.current, null);
+    |                                    ^^^^^^^^^^^ Ref is initially accessed
   6 |
   7 |   return <Stringify state={state} />;
   8 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-access-ref-in-render-mutate-object-with-ref-function.expect.md

@@ -1,37 +0,0 @@
-
-## Input
-
-```javascript
-import {useRef} from 'react';
-
-function Component() {
-  const ref = useRef(null);
-  const object = {};
-  object.foo = () => ref.current;
-  const refValue = object.foo();
-  return <div>{refValue}</div>;
-}
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.invalid-access-ref-in-render-mutate-object-with-ref-function.ts:7:19
-   5 |   const object = {};
-   6 |   object.foo = () => ref.current;
->  7 |   const refValue = object.foo();
-     |                    ^^^^^^^^^^ This function accesses a ref value
-   8 |   return <div>{refValue}</div>;
-   9 | }
-  10 |
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-access-ref-in-state-initializer.expect.md

@@ -24,7 +24,7 @@ export const FIXTURE_ENTRYPOINT = {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -32,7 +32,16 @@ error.invalid-access-ref-in-state-initializer.ts:5:27
   3 | function Component(props) {
   4 |   const ref = useRef(props.value);
 > 5 |   const [state] = useState(() => ref.current);
-    |                            ^^^^^^^^^^^^^^^^^ Passing a ref to a function may read its value during render
+    |                            ^^^^^^^^^^^^^^^^^ Ref value is used during render
+  6 |
+  7 |   return <Stringify state={state} />;
+  8 | }
+
+error.invalid-access-ref-in-state-initializer.ts:5:33
+  3 | function Component(props) {
+  4 |   const ref = useRef(props.value);
+> 5 |   const [state] = useState(() => ref.current);
+    |                                  ^^^^^^^^^^^ Ref is initially accessed
   6 |
   7 |   return <Stringify state={state} />;
   8 | }

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

@@ -21,17 +21,27 @@ function Component(props) {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-error.invalid-aliased-ref-in-callback-invoked-during-render-.ts:9:33
-   7 |     return <Foo item={item} current={current} />;
+error.invalid-aliased-ref-in-callback-invoked-during-render-.ts:7:37
+   5 |     const aliasedRef = ref;
+   6 |     const current = aliasedRef.current;
+>  7 |     return <Foo item={item} current={current} />;
+     |                                      ^^^^^^^ Ref value is used during render
    8 |   };
->  9 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
-     |                                  ^^^^^^^^^^^^^^^^^^^^^^^^ Cannot access ref value during render
+   9 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
   10 | }
-  11 |
+
+error.invalid-aliased-ref-in-callback-invoked-during-render-.ts:6:20
+  4 |   const renderItem = item => {
+  5 |     const aliasedRef = ref;
+> 6 |     const current = aliasedRef.current;
+    |                     ^^^^^^^^^^^^^^^^^^ Ref is initially accessed
+  7 |     return <Foo item={item} current={current} />;
+  8 |   };
+  9 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
 ```
           
       

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

@@ -27,14 +27,14 @@ Error: Cannot access refs during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-error.invalid-disallow-mutating-refs-in-render-transitive.ts:9:2
-   7 |   };
-   8 |   const changeRef = setRef;
->  9 |   changeRef();
-     |   ^^^^^^^^^ This function accesses a ref value
-  10 |
-  11 |   return <button ref={ref} />;
-  12 | }
+error.invalid-disallow-mutating-refs-in-render-transitive.ts:6:4
+  4 |
+  5 |   const setRef = () => {
+> 6 |     ref.current = false;
+    |     ^^^^^^^^^^^ Cannot update ref during render
+  7 |   };
+  8 |   const changeRef = setRef;
+  9 |   changeRef();
 ```
           
       

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

@@ -0,0 +1,50 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+function Component() {
+  const now = Date.now();
+  const f = () => {
+    const array = makeArray(now);
+    const hasDate = identity(array);
+    return hasDate;
+  };
+  const hasDate = f();
+  return <Foo hasDate={hasDate} />;
+}
+
+```
+
+
+## Error
+
+```
+Found 1 error:
+
+Error: Cannot access impure value during render
+
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render-via-function-call.ts:13:23
+  11 |   };
+  12 |   const hasDate = f();
+> 13 |   return <Foo hasDate={hasDate} />;
+     |                        ^^^^^^^ Cannot access impure value during render
+  14 | }
+  15 |
+
+error.invalid-impure-functions-in-render-via-function-call.ts:6:14
+  4 |
+  5 | function Component() {
+> 6 |   const now = Date.now();
+    |               ^^^^^^^^^^ `Date.now` is an impure function.
+  7 |   const f = () => {
+  8 |     const array = makeArray(now);
+  9 |     const hasDate = identity(array);
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-impure-functions-in-render-via-function-call.js

@@ -0,0 +1,14 @@
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+function Component() {
+  const now = Date.now();
+  const f = () => {
+    const array = makeArray(now);
+    const hasDate = identity(array);
+    return hasDate;
+  };
+  const hasDate = f();
+  return <Foo hasDate={hasDate} />;
+}

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

@@ -0,0 +1,50 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+
+import {typedArrayPush, typedIdentity} from 'shared-runtime';
+
+function Component() {
+  const now = Date.now();
+  const renderItem = () => {
+    const array = [];
+    typedArrayPush(array, now());
+    const hasDate = typedIdentity(array);
+    return <Bar hasDate={hasDate} />;
+  };
+  return <Foo renderItem={renderItem} />;
+}
+
+```
+
+
+## Error
+
+```
+Found 1 error:
+
+Error: Cannot access impure value during render
+
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render-via-render-helper-typed.ts:13:26
+  11 |     return <Bar hasDate={hasDate} />;
+  12 |   };
+> 13 |   return <Foo renderItem={renderItem} />;
+     |                           ^^^^^^^^^^ Cannot access impure value during render
+  14 | }
+  15 |
+
+error.invalid-impure-functions-in-render-via-render-helper-typed.ts:6:14
+  4 |
+  5 | function Component() {
+> 6 |   const now = Date.now();
+    |               ^^^^^^^^^^ `Date.now` is an impure function.
+  7 |   const renderItem = () => {
+  8 |     const array = [];
+  9 |     typedArrayPush(array, now());
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-impure-functions-in-render-via-render-helper-typed.js

@@ -0,0 +1,14 @@
+// @validateNoImpureFunctionsInRender
+
+import {typedArrayPush, typedIdentity} from 'shared-runtime';
+
+function Component() {
+  const now = Date.now();
+  const renderItem = () => {
+    const array = [];
+    typedArrayPush(array, now());
+    const hasDate = typedIdentity(array);
+    return <Bar hasDate={hasDate} />;
+  };
+  return <Foo renderItem={renderItem} />;
+}

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

@@ -0,0 +1,49 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+function Component() {
+  const now = Date.now();
+  const renderItem = () => {
+    const array = makeArray(now);
+    const hasDate = identity(array);
+    return <Bar hasDate={hasDate} />;
+  };
+  return <Foo renderItem={renderItem} />;
+}
+
+```
+
+
+## Error
+
+```
+Found 1 error:
+
+Error: Cannot access impure value during render
+
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render-via-render-helper.ts:12:26
+  10 |     return <Bar hasDate={hasDate} />;
+  11 |   };
+> 12 |   return <Foo renderItem={renderItem} />;
+     |                           ^^^^^^^^^^ Cannot access impure value during render
+  13 | }
+  14 |
+
+error.invalid-impure-functions-in-render-via-render-helper.ts:6:14
+  4 |
+  5 | function Component() {
+> 6 |   const now = Date.now();
+    |               ^^^^^^^^^^ `Date.now` is an impure function.
+  7 |   const renderItem = () => {
+  8 |     const array = makeArray(now);
+  9 |     const hasDate = identity(array);
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-impure-functions-in-render-via-render-helper.js

@@ -0,0 +1,13 @@
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+function Component() {
+  const now = Date.now();
+  const renderItem = () => {
+    const array = makeArray(now);
+    const hasDate = identity(array);
+    return <Bar hasDate={hasDate} />;
+  };
+  return <Foo renderItem={renderItem} />;
+}

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

@@ -19,41 +19,65 @@ function Component() {
 ```
 Found 3 errors:
 
-Error: Cannot call impure function during render
+Error: Cannot access impure value during render
 
-`Date.now` is an impure function. Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render.ts:7:20
+  5 |   const now = performance.now();
+  6 |   const rand = Math.random();
+> 7 |   return <Foo date={date} now={now} rand={rand} />;
+    |                     ^^^^ Cannot access impure value during render
+  8 | }
+  9 |
 
 error.invalid-impure-functions-in-render.ts:4:15
   2 |
   3 | function Component() {
 > 4 |   const date = Date.now();
-    |                ^^^^^^^^^^ Cannot call impure function
+    |                ^^^^^^^^^^ `Date.now` is an impure function.
   5 |   const now = performance.now();
   6 |   const rand = Math.random();
   7 |   return <Foo date={date} now={now} rand={rand} />;
 
-Error: Cannot call impure function during render
+Error: Cannot access impure value during render
 
-`performance.now` is an impure function. Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render.ts:7:31
+  5 |   const now = performance.now();
+  6 |   const rand = Math.random();
+> 7 |   return <Foo date={date} now={now} rand={rand} />;
+    |                                ^^^ Cannot access impure value during render
+  8 | }
+  9 |
 
 error.invalid-impure-functions-in-render.ts:5:14
   3 | function Component() {
   4 |   const date = Date.now();
 > 5 |   const now = performance.now();
-    |               ^^^^^^^^^^^^^^^^^ Cannot call impure function
+    |               ^^^^^^^^^^^^^^^^^ `performance.now` is an impure function.
   6 |   const rand = Math.random();
   7 |   return <Foo date={date} now={now} rand={rand} />;
   8 | }
 
-Error: Cannot call impure function during render
+Error: Cannot access impure value during render
 
-`Math.random` is an impure function. Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render.ts:7:42
+  5 |   const now = performance.now();
+  6 |   const rand = Math.random();
+> 7 |   return <Foo date={date} now={now} rand={rand} />;
+    |                                           ^^^^ Cannot access impure value during render
+  8 | }
+  9 |
 
 error.invalid-impure-functions-in-render.ts:6:15
   4 |   const date = Date.now();
   5 |   const now = performance.now();
 > 6 |   const rand = Math.random();
-    |                ^^^^^^^^^^^^^ Cannot call impure function
+    |                ^^^^^^^^^^^^^ `Math.random` is an impure function.
   7 |   return <Foo date={date} now={now} rand={rand} />;
   8 | }
   9 |

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

@@ -0,0 +1,45 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+function Component() {
+  const now = () => Date.now();
+  const render = () => {
+    return <div>{now()}</div>;
+  };
+  return <div>{render()}</div>;
+}
+
+```
+
+
+## Error
+
+```
+Found 1 error:
+
+Error: Cannot access impure value during render
+
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-value-in-render-helper.ts:5:17
+  3 |   const now = () => Date.now();
+  4 |   const render = () => {
+> 5 |     return <div>{now()}</div>;
+    |                  ^^^^^ Cannot access impure value during render
+  6 |   };
+  7 |   return <div>{render()}</div>;
+  8 | }
+
+error.invalid-impure-value-in-render-helper.ts:3:20
+  1 | // @validateNoImpureFunctionsInRender
+  2 | function Component() {
+> 3 |   const now = () => Date.now();
+    |                     ^^^^^^^^^^ `Date.now` is an impure function.
+  4 |   const render = () => {
+  5 |     return <div>{now()}</div>;
+  6 |   };
+```
+          
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-impure-value-in-render-helper.js

@@ -0,0 +1,8 @@
+// @validateNoImpureFunctionsInRender
+function Component() {
+  const now = () => Date.now();
+  const render = () => {
+    return <div>{now()}</div>;
+  };
+  return <div>{render()}</div>;
+}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-pass-ref-to-function.expect.md

@@ -1,34 +0,0 @@
-
-## Input
-
-```javascript
-// @validateRefAccessDuringRender
-function Component(props) {
-  const ref = useRef(null);
-  const x = foo(ref);
-  return x.current;
-}
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.invalid-pass-ref-to-function.ts:4:16
-  2 | function Component(props) {
-  3 |   const ref = useRef(null);
-> 4 |   const x = foo(ref);
-    |                 ^^^ Passing a ref to a function may read its value during render
-  5 |   return x.current;
-  6 | }
-  7 |
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-pass-ref-to-function.js

@@ -1,6 +0,0 @@
-// @validateRefAccessDuringRender
-function Component(props) {
-  const ref = useRef(null);
-  const x = foo(ref);
-  return x.current;
-}

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

@@ -16,15 +16,23 @@ function Component({ref}) {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
+error.invalid-read-ref-prop-in-render-destructure.ts:4:15
+  2 | function Component({ref}) {
+  3 |   const value = ref.current;
+> 4 |   return <div>{value}</div>;
+    |                ^^^^^ Ref value is used during render
+  5 | }
+  6 |
+
 error.invalid-read-ref-prop-in-render-destructure.ts:3:16
   1 | // @validateRefAccessDuringRender @compilationMode:"infer"
   2 | function Component({ref}) {
 > 3 |   const value = ref.current;
-    |                 ^^^^^^^^^^^ Cannot access ref value during render
+    |                 ^^^^^^^^^^^ Ref is initially accessed
   4 |   return <div>{value}</div>;
   5 | }
   6 |

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

@@ -16,15 +16,23 @@ function Component(props) {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
+error.invalid-read-ref-prop-in-render-property-load.ts:4:15
+  2 | function Component(props) {
+  3 |   const value = props.ref.current;
+> 4 |   return <div>{value}</div>;
+    |                ^^^^^ Ref value is used during render
+  5 | }
+  6 |
+
 error.invalid-read-ref-prop-in-render-property-load.ts:3:16
   1 | // @validateRefAccessDuringRender @compilationMode:"infer"
   2 | function Component(props) {
 > 3 |   const value = props.ref.current;
-    |                 ^^^^^^^^^^^^^^^^^ Cannot access ref value during render
+    |                 ^^^^^^^^^^^^^^^^^ Ref is initially accessed
   4 |   return <div>{value}</div>;
   5 | }
   6 |

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

@@ -22,57 +22,27 @@ export const FIXTURE_ENTRYPOINT = {
 ## Error
 
 ```
-Found 4 errors:
+Found 1 error:
 
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-  4 | component C() {
-  5 |   const r = useRef(null);
-> 6 |   const current = !r.current;
-    |                    ^^^^^^^^^ Cannot access ref value during render
-  7 |   return <div>{current}</div>;
-  8 | }
-  9 |
-
-To initialize a ref only once, check that the ref is null with the pattern `if (ref.current == null) { ref.current = ... }`
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-  4 | component C() {
-  5 |   const r = useRef(null);
-> 6 |   const current = !r.current;
-    |                   ^^^^^^^^^^ Cannot access ref value during render
-  7 |   return <div>{current}</div>;
-  8 | }
-  9 |
-
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
    5 |   const r = useRef(null);
    6 |   const current = !r.current;
 >  7 |   return <div>{current}</div>;
-     |                ^^^^^^^ Cannot access ref value during render
+     |                ^^^^^^^ Ref value is used during render
    8 | }
    9 |
   10 | export const FIXTURE_ENTRYPOINT = {
 
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   5 |   const r = useRef(null);
-   6 |   const current = !r.current;
->  7 |   return <div>{current}</div>;
-     |                ^^^^^^^ Cannot access ref value during render
-   8 | }
-   9 |
-  10 | export const FIXTURE_ENTRYPOINT = {
+  4 | component C() {
+  5 |   const r = useRef(null);
+> 6 |   const current = !r.current;
+    |                    ^^^^^^^^^ Ref is initially accessed
+  7 |   return <div>{current}</div>;
+  8 | }
+  9 |
 ```
           
       

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

@@ -20,17 +20,27 @@ function Component(props) {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-error.invalid-ref-in-callback-invoked-during-render.ts:8:33
-   6 |     return <Foo item={item} current={current} />;
-   7 |   };
->  8 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
-     |                                  ^^^^^^^^^^^^^^^^^^^^^^^^ Cannot access ref value during render
-   9 | }
-  10 |
+error.invalid-ref-in-callback-invoked-during-render.ts:6:37
+  4 |   const renderItem = item => {
+  5 |     const current = ref.current;
+> 6 |     return <Foo item={item} current={current} />;
+    |                                      ^^^^^^^ Ref value is used during render
+  7 |   };
+  8 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
+  9 | }
+
+error.invalid-ref-in-callback-invoked-during-render.ts:5:20
+  3 |   const ref = useRef(null);
+  4 |   const renderItem = item => {
+> 5 |     const current = ref.current;
+    |                     ^^^^^^^^^^^ Ref is initially accessed
+  6 |     return <Foo item={item} current={current} />;
+  7 |   };
+  8 |   return <Items>{props.items.map(item => renderItem(item))}</Items>;
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-ref-initialization-unary-not.expect.md

@@ -29,15 +29,13 @@ Error: Cannot access refs during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-  4 | component C() {
-  5 |   const r = useRef(null);
-> 6 |   if (!r.current) {
-    |        ^^^^^^^^^ Cannot access ref value during render
-  7 |     r.current = 1;
-  8 |   }
-  9 | }
-
-To initialize a ref only once, check that the ref is null with the pattern `if (ref.current == null) { ref.current = ... }`
+   5 |   const r = useRef(null);
+   6 |   if (!r.current) {
+>  7 |     r.current = 1;
+     |     ^^^^^^^^^ Cannot update ref during render
+   8 |   }
+   9 | }
+  10 |
 ```
           
       

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

@@ -16,7 +16,7 @@ function Component(props) {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -24,7 +24,7 @@ error.invalid-ref-value-as-props.ts:4:19
   2 | function Component(props) {
   3 |   const ref = useRef(null);
 > 4 |   return <Foo ref={ref.current} />;
-    |                    ^^^^^^^^^^^ Cannot access ref value during render
+    |                    ^^^^^^^^^^^ Ref value is used during render
   5 | }
   6 |
 ```

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

@@ -15,22 +15,9 @@ function Component(props) {
 ## Error
 
 ```
-Found 2 errors:
+Found 1 error:
 
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.invalid-set-and-read-ref-during-render.ts:4:2
-  2 | function Component(props) {
-  3 |   const ref = useRef(null);
-> 4 |   ref.current = props.value;
-    |   ^^^^^^^^^^^ Cannot update ref during render
-  5 |   return ref.current;
-  6 | }
-  7 |
-
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -38,7 +25,7 @@ error.invalid-set-and-read-ref-during-render.ts:5:9
   3 |   const ref = useRef(null);
   4 |   ref.current = props.value;
 > 5 |   return ref.current;
-    |          ^^^^^^^^^^^ Cannot access ref value during render
+    |          ^^^^^^^^^^^ Ref value is used during render
   6 | }
   7 |
 ```

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-set-and-read-ref-nested-property-during-render.expect.md

@@ -15,22 +15,9 @@ function Component(props) {
 ## Error
 
 ```
-Found 2 errors:
+Found 1 error:
 
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.invalid-set-and-read-ref-nested-property-during-render.ts:4:2
-  2 | function Component(props) {
-  3 |   const ref = useRef({inner: null});
-> 4 |   ref.current.inner = props.value;
-    |   ^^^^^^^^^^^ Cannot update ref during render
-  5 |   return ref.current.inner;
-  6 | }
-  7 |
-
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -38,7 +25,15 @@ error.invalid-set-and-read-ref-nested-property-during-render.ts:5:9
   3 |   const ref = useRef({inner: null});
   4 |   ref.current.inner = props.value;
 > 5 |   return ref.current.inner;
-    |          ^^^^^^^^^^^^^^^^^ Cannot access ref value during render
+    |          ^^^^^^^^^^^^^^^^^ Ref value is used during render
+  6 | }
+  7 |
+
+error.invalid-set-and-read-ref-nested-property-during-render.ts:5:9
+  3 |   const ref = useRef({inner: null});
+  4 |   ref.current.inner = props.value;
+> 5 |   return ref.current.inner;
+    |          ^^^^^^^^^^^ Ref is initially accessed
   6 | }
   7 |
 ```

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-use-ref-added-to-dep-without-type-info.expect.md

@@ -1,53 +0,0 @@
-
-## Input
-
-```javascript
-// @validateRefAccessDuringRender
-function Foo({a}) {
-  const ref = useRef();
-  // type information is lost here as we don't track types of fields
-  const val = {ref};
-  // without type info, we don't know that val.ref.current is a ref value so we
-  // *would* end up depending on val.ref.current
-  // however, this is an instance of accessing a ref during render and is disallowed
-  // under React's rules, so we reject this input
-  const x = {a, val: val.ref.current};
-
-  return <VideoList videos={x} />;
-}
-
-```
-
-
-## Error
-
-```
-Found 2 errors:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.invalid-use-ref-added-to-dep-without-type-info.ts:10:21
-   8 |   // however, this is an instance of accessing a ref during render and is disallowed
-   9 |   // under React's rules, so we reject this input
-> 10 |   const x = {a, val: val.ref.current};
-     |                      ^^^^^^^^^^^^^^^ Cannot access ref value during render
-  11 |
-  12 |   return <VideoList videos={x} />;
-  13 | }
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.invalid-use-ref-added-to-dep-without-type-info.ts:12:28
-  10 |   const x = {a, val: val.ref.current};
-  11 |
-> 12 |   return <VideoList videos={x} />;
-     |                             ^ Cannot access ref value during render
-  13 | }
-  14 |
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.invalid-use-ref-added-to-dep-without-type-info.js

@@ -1,13 +0,0 @@
-// @validateRefAccessDuringRender
-function Foo({a}) {
-  const ref = useRef();
-  // type information is lost here as we don't track types of fields
-  const val = {ref};
-  // without type info, we don't know that val.ref.current is a ref value so we
-  // *would* end up depending on val.ref.current
-  // however, this is an instance of accessing a ref during render and is disallowed
-  // under React's rules, so we reject this input
-  const x = {a, val: val.ref.current};
-
-  return <VideoList videos={x} />;
-}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-initialization-arbitrary.expect.md

@@ -25,19 +25,7 @@ export const FIXTURE_ENTRYPOINT = {
 ## Error
 
 ```
-Found 2 errors:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   6 | component C() {
-   7 |   const r = useRef(DEFAULT_VALUE);
->  8 |   if (r.current == DEFAULT_VALUE) {
-     |       ^^^^^^^^^ Cannot access ref value during render
-   9 |     r.current = 1;
-  10 |   }
-  11 | }
+Found 1 error:
 
 Error: Cannot access refs during render
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-initialization-call-2.expect.md

@@ -1,41 +0,0 @@
-
-## Input
-
-```javascript
-//@flow
-import {useRef} from 'react';
-
-component C() {
-  const r = useRef(null);
-  if (r.current == null) {
-    f(r);
-  }
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: C,
-  params: [{}],
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   5 |   const r = useRef(null);
-   6 |   if (r.current == null) {
->  7 |     f(r);
-     |       ^ Passing a ref to a function may read its value during render
-   8 |   }
-   9 | }
-  10 |
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-initialization-call.expect.md

@@ -1,41 +0,0 @@
-
-## Input
-
-```javascript
-//@flow
-import {useRef} from 'react';
-
-component C() {
-  const r = useRef(null);
-  if (r.current == null) {
-    f(r.current);
-  }
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: C,
-  params: [{}],
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   5 |   const r = useRef(null);
-   6 |   if (r.current == null) {
->  7 |     f(r.current);
-     |       ^^^^^^^^^ Passing a ref to a function may read its value during render
-   8 |   }
-   9 | }
-  10 |
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-initialization-linear.expect.md

@@ -33,10 +33,18 @@ React refs are values that are not needed for rendering. Refs should only be acc
    6 |   if (r.current == null) {
    7 |     r.current = 42;
 >  8 |     r.current = 42;
-     |     ^^^^^^^^^ Cannot update ref during render
+     |     ^^^^^^^^^ Ref is initialized more than once during render
    9 |   }
   10 | }
   11 |
+
+   5 |   const r = useRef(null);
+   6 |   if (r.current == null) {
+>  7 |     r.current = 42;
+     |     ^^^^^^^^^ Ref was first initialized here
+   8 |     r.current = 42;
+   9 |   }
+  10 | }
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-initialization-nonif.expect.md

@@ -24,31 +24,19 @@ export const FIXTURE_ENTRYPOINT = {
 ## Error
 
 ```
-Found 2 errors:
+Found 1 error:
 
 Error: Cannot access refs during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-  4 | component C() {
-  5 |   const r = useRef(null);
-> 6 |   const guard = r.current == null;
-    |                 ^^^^^^^^^^^^^^^^^ Cannot access ref value during render
-  7 |   if (guard) {
-  8 |     r.current = 1;
-  9 |   }
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   5 |   const r = useRef(null);
    6 |   const guard = r.current == null;
->  7 |   if (guard) {
-     |       ^^^^^ Cannot access ref value during render
-   8 |     r.current = 1;
+   7 |   if (guard) {
+>  8 |     r.current = 1;
+     |     ^^^^^^^^^ Cannot update ref during render
    9 |   }
   10 | }
+  11 |
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-initialization-post-access-2.expect.md

@@ -1,42 +0,0 @@
-
-## Input
-
-```javascript
-//@flow
-import {useRef} from 'react';
-
-component C() {
-  const r = useRef(null);
-  if (r.current == null) {
-    r.current = 1;
-  }
-  f(r.current);
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: C,
-  params: [{}],
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   7 |     r.current = 1;
-   8 |   }
->  9 |   f(r.current);
-     |     ^^^^^^^^^ Passing a ref to a function may read its value during render
-  10 | }
-  11 |
-  12 | export const FIXTURE_ENTRYPOINT = {
-```
-          
-      

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

@@ -22,7 +22,7 @@ export const FIXTURE_ENTRYPOINT = {
 ```
 Found 1 error:
 
-Error: Cannot access refs during render
+Error: Cannot access ref value during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
@@ -30,7 +30,7 @@ error.ref-optional.ts:5:9
   3 | function Component(props) {
   4 |   const ref = useRef();
 > 5 |   return ref?.current;
-    |          ^^^^^^^^^^^^ Cannot access ref value during render
+    |          ^^^^^^^^^^^^ Ref value is used during render
   6 | }
   7 |
   8 | export const FIXTURE_ENTRYPOINT = {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-value-in-custom-component-event-handler-wrapper.expect.md

@@ -1,69 +0,0 @@
-
-## Input
-
-```javascript
-// @enableInferEventHandlers
-import {useRef} from 'react';
-
-// Simulates a custom component wrapper
-function CustomForm({onSubmit, children}: any) {
-  return <form onSubmit={onSubmit}>{children}</form>;
-}
-
-// Simulates react-hook-form's handleSubmit
-function handleSubmit<T>(callback: (data: T) => void) {
-  return (event: any) => {
-    event.preventDefault();
-    callback({} as T);
-  };
-}
-
-function Component() {
-  const ref = useRef<HTMLInputElement>(null);
-
-  const onSubmit = (data: any) => {
-    // This should error: passing function with ref access to custom component
-    // event handler, even though it would be safe on a native <form>
-    if (ref.current !== null) {
-      console.log(ref.current.value);
-    }
-  };
-
-  return (
-    <>
-      <input ref={ref} />
-      <CustomForm onSubmit={handleSubmit(onSubmit)}>
-        <button type="submit">Submit</button>
-      </CustomForm>
-    </>
-  );
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: Component,
-  params: [{}],
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.ref-value-in-custom-component-event-handler-wrapper.ts:31:41
-  29 |     <>
-  30 |       <input ref={ref} />
-> 31 |       <CustomForm onSubmit={handleSubmit(onSubmit)}>
-     |                                          ^^^^^^^^ Passing a ref to a function may read its value during render
-  32 |         <button type="submit">Submit</button>
-  33 |       </CustomForm>
-  34 |     </>
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.ref-value-in-event-handler-wrapper.expect.md

@@ -1,55 +0,0 @@
-
-## Input
-
-```javascript
-// @enableInferEventHandlers
-import {useRef} from 'react';
-
-// Simulates a handler wrapper
-function handleClick(value: any) {
-  return () => {
-    console.log(value);
-  };
-}
-
-function Component() {
-  const ref = useRef(null);
-
-  // This should still error: passing ref.current directly to a wrapper
-  // The ref value is accessed during render, not in the event handler
-  return (
-    <>
-      <input ref={ref} />
-      <button onClick={handleClick(ref.current)}>Click</button>
-    </>
-  );
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: Component,
-  params: [{}],
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.ref-value-in-event-handler-wrapper.ts:19:35
-  17 |     <>
-  18 |       <input ref={ref} />
-> 19 |       <button onClick={handleClick(ref.current)}>Click</button>
-     |                                    ^^^^^^^^^^^ Cannot access ref value during render
-  20 |     </>
-  21 |   );
-  22 | }
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.todo-useCallback-set-ref-nested-property-ref-modified-later-preserve-memoization.expect.md

@@ -41,7 +41,7 @@ error.todo-useCallback-set-ref-nested-property-ref-modified-later-preserve-memoi
   12 |
   13 |   // The ref is modified later, extending its range and preventing memoization of onChange
 > 14 |   ref.current.inner = null;
-     |   ^^^^^^^^^^^ Cannot update ref during render
+     |   ^^^^^^^^^^^^^^^^^ Cannot update ref during render
   15 |
   16 |   return <input onChange={onChange} />;
   17 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.useCallback-accesses-ref-mutated-later-via-function-preserve-memoization.expect.md

@@ -40,14 +40,14 @@ Error: Cannot access refs during render
 
 React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
 
-error.useCallback-accesses-ref-mutated-later-via-function-preserve-memoization.ts:17:2
-  15 |     ref.current.inner = null;
+error.useCallback-accesses-ref-mutated-later-via-function-preserve-memoization.ts:15:4
+  13 |   // The ref is modified later, extending its range and preventing memoization of onChange
+  14 |   const reset = () => {
+> 15 |     ref.current.inner = null;
+     |     ^^^^^^^^^^^^^^^^^ Cannot update ref during render
   16 |   };
-> 17 |   reset();
-     |   ^^^^^ This function accesses a ref value
+  17 |   reset();
   18 |
-  19 |   return <input onChange={onChange} />;
-  20 | }
 ```
           
       

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.useCallback-set-ref-nested-property-dont-preserve-memoization.expect.md

@@ -40,7 +40,7 @@ error.useCallback-set-ref-nested-property-dont-preserve-memoization.ts:13:2
   11 |   });
   12 |
 > 13 |   ref.current.inner = null;
-     |   ^^^^^^^^^^^ Cannot update ref during render
+     |   ^^^^^^^^^^^^^^^^^ Cannot update ref during render
   14 |
   15 |   return <input onChange={onChange} />;
   16 | }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/error.validate-mutate-ref-arg-in-render.expect.md

@@ -1,39 +0,0 @@
-
-## Input
-
-```javascript
-// @validateRefAccessDuringRender:true
-function Foo(props, ref) {
-  console.log(ref.current);
-  return <div>{props.bar}</div>;
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: Foo,
-  params: [{bar: 'foo'}, {ref: {cuurrent: 1}}],
-  isComponent: true,
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.validate-mutate-ref-arg-in-render.ts:3:14
-  1 | // @validateRefAccessDuringRender:true
-  2 | function Foo(props, ref) {
-> 3 |   console.log(ref.current);
-    |               ^^^^^^^^^^^ Passing a ref to a function may read its value during render
-  4 |   return <div>{props.bar}</div>;
-  5 | }
-  6 |
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/exhaustive-deps/error.invalid-exhaustive-deps.expect.md

@@ -2,7 +2,7 @@
 ## Input
 
 ```javascript
-// @validateExhaustiveMemoizationDependencies
+// @validateExhaustiveMemoizationDependencies @validateRefAccessDuringRender:false
 import {useMemo} from 'react';
 import {Stringify} from 'shared-runtime';
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/exhaustive-deps/error.invalid-exhaustive-deps.js

@@ -1,4 +1,4 @@
-// @validateExhaustiveMemoizationDependencies
+// @validateExhaustiveMemoizationDependencies @validateRefAccessDuringRender:false
 import {useMemo} from 'react';
 import {Stringify} from 'shared-runtime';
 

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/impure-functions-in-render-indirect-via-mutation.expect.md

@@ -0,0 +1,58 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+
+import {arrayPush, identity, makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const getDate = () => Date.now();
+  const now = getDate();
+  const array = [];
+  arrayPush(array, now);
+  return <Foo hasDate={array} />;
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @validateNoImpureFunctionsInRender
+
+import { arrayPush, identity, makeArray } from "shared-runtime";
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const $ = _c(1);
+  const getDate = _temp;
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    const now = getDate();
+    const array = [];
+    arrayPush(array, now);
+    t0 = <Foo hasDate={array} />;
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+function _temp() {
+  return Date.now();
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/impure-functions-in-render-indirect-via-mutation.js

@@ -0,0 +1,16 @@
+// @validateNoImpureFunctionsInRender
+
+import {arrayPush, identity, makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const getDate = () => Date.now();
+  const now = getDate();
+  const array = [];
+  arrayPush(array, now);
+  return <Foo hasDate={array} />;
+}

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

@@ -0,0 +1,56 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const getDate = () => Date.now();
+  const array = makeArray(getDate());
+  const hasDate = identity(array);
+  return <Foo hasDate={hasDate} />;
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @validateNoImpureFunctionsInRender
+
+import { identity, makeArray } from "shared-runtime";
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const $ = _c(1);
+  const getDate = _temp;
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    const array = makeArray(getDate());
+    const hasDate = identity(array);
+    t0 = <Foo hasDate={hasDate} />;
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+function _temp() {
+  return Date.now();
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/impure-functions-in-render-indirect.js

@@ -0,0 +1,15 @@
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const getDate = () => Date.now();
+  const array = makeArray(getDate());
+  const hasDate = identity(array);
+  return <Foo hasDate={hasDate} />;
+}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/impure-functions-in-render-via-function-call-2.expect.md

@@ -0,0 +1,64 @@
+
+## Input
+
+```javascript
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const now = () => Date.now();
+  const f = () => {
+    const array = makeArray(now());
+    const hasDate = identity(array);
+    return hasDate;
+  };
+  const hasDate = f();
+  return <Foo hasDate={hasDate} />;
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @validateNoImpureFunctionsInRender
+
+import { identity, makeArray } from "shared-runtime";
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const $ = _c(1);
+  const now = _temp;
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    const f = () => {
+      const array = makeArray(now());
+      const hasDate = identity(array);
+      return hasDate;
+    };
+    const hasDate_0 = f();
+    t0 = <Foo hasDate={hasDate_0} />;
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+function _temp() {
+  return Date.now();
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/impure-functions-in-render-via-function-call-2.js

@@ -0,0 +1,19 @@
+// @validateNoImpureFunctionsInRender
+
+import {identity, makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render. The impurity is lost
+ * when passed through external function calls.
+ */
+function Component() {
+  const now = () => Date.now();
+  const f = () => {
+    const array = makeArray(now());
+    const hasDate = identity(array);
+    return hasDate;
+  };
+  const hasDate = f();
+  return <Foo hasDate={hasDate} />;
+}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/infer-effect-dependencies/bailout-retry/mutate-after-useeffect-ref-access.expect.md

@@ -47,7 +47,7 @@ export const FIXTURE_ENTRYPOINT = {
 ## Logs
 
 ```
-{"kind":"CompileError","fnLoc":{"start":{"line":6,"column":0,"index":158},"end":{"line":11,"column":1,"index":331},"filename":"mutate-after-useeffect-ref-access.ts"},"detail":{"options":{"category":"Refs","reason":"Cannot access refs during render","description":"React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef)","details":[{"kind":"error","loc":{"start":{"line":9,"column":2,"index":289},"end":{"line":9,"column":16,"index":303},"filename":"mutate-after-useeffect-ref-access.ts"},"message":"Cannot update ref during render"}]}}}
+{"kind":"CompileError","fnLoc":{"start":{"line":6,"column":0,"index":158},"end":{"line":11,"column":1,"index":331},"filename":"mutate-after-useeffect-ref-access.ts"},"detail":{"options":{"category":"Refs","reason":"Cannot access refs during render","description":"React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef)","details":[{"kind":"error","loc":{"start":{"line":9,"column":2,"index":289},"end":{"line":9,"column":20,"index":307},"filename":"mutate-after-useeffect-ref-access.ts"},"message":"Cannot update ref during render"}]}}}
 {"kind":"AutoDepsDecorations","fnLoc":{"start":{"line":8,"column":2,"index":237},"end":{"line":8,"column":50,"index":285},"filename":"mutate-after-useeffect-ref-access.ts"},"decorations":[{"start":{"line":8,"column":24,"index":259},"end":{"line":8,"column":30,"index":265},"filename":"mutate-after-useeffect-ref-access.ts","identifierName":"arrRef"}]}
 {"kind":"CompileSuccess","fnLoc":{"start":{"line":6,"column":0,"index":158},"end":{"line":11,"column":1,"index":331},"filename":"mutate-after-useeffect-ref-access.ts"},"fnName":"Component","memoSlots":0,"memoBlocks":0,"memoValues":0,"prunedMemoBlocks":0,"prunedMemoValues":0}
 ```

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

@@ -19,41 +19,65 @@ function Component() {
 ```
 Found 3 errors:
 
-Error: Cannot call impure function during render
+Error: Cannot access impure value during render
 
-`Date.now` is an impure function. Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render.ts:7:20
+  5 |   const now = performance.now();
+  6 |   const rand = Math.random();
+> 7 |   return <Foo date={date} now={now} rand={rand} />;
+    |                     ^^^^ Cannot access impure value during render
+  8 | }
+  9 |
 
 error.invalid-impure-functions-in-render.ts:4:15
   2 |
   3 | function Component() {
 > 4 |   const date = Date.now();
-    |                ^^^^^^^^^^ Cannot call impure function
+    |                ^^^^^^^^^^ `Date.now` is an impure function.
   5 |   const now = performance.now();
   6 |   const rand = Math.random();
   7 |   return <Foo date={date} now={now} rand={rand} />;
 
-Error: Cannot call impure function during render
+Error: Cannot access impure value during render
 
-`performance.now` is an impure function. Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render.ts:7:31
+  5 |   const now = performance.now();
+  6 |   const rand = Math.random();
+> 7 |   return <Foo date={date} now={now} rand={rand} />;
+    |                                ^^^ Cannot access impure value during render
+  8 | }
+  9 |
 
 error.invalid-impure-functions-in-render.ts:5:14
   3 | function Component() {
   4 |   const date = Date.now();
 > 5 |   const now = performance.now();
-    |               ^^^^^^^^^^^^^^^^^ Cannot call impure function
+    |               ^^^^^^^^^^^^^^^^^ `performance.now` is an impure function.
   6 |   const rand = Math.random();
   7 |   return <Foo date={date} now={now} rand={rand} />;
   8 | }
 
-Error: Cannot call impure function during render
+Error: Cannot access impure value during render
 
-`Math.random` is an impure function. Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+Calling an impure function can produce unstable results that update unpredictably when the component happens to re-render. (https://react.dev/reference/rules/components-and-hooks-must-be-pure#components-and-hooks-must-be-idempotent).
+
+error.invalid-impure-functions-in-render.ts:7:42
+  5 |   const now = performance.now();
+  6 |   const rand = Math.random();
+> 7 |   return <Foo date={date} now={now} rand={rand} />;
+    |                                           ^^^^ Cannot access impure value during render
+  8 | }
+  9 |
 
 error.invalid-impure-functions-in-render.ts:6:15
   4 |   const date = Date.now();
   5 |   const now = performance.now();
 > 6 |   const rand = Math.random();
-    |                ^^^^^^^^^^^^^ Cannot call impure function
+    |                ^^^^^^^^^^^^^ `Math.random` is an impure function.
   7 |   return <Foo date={date} now={now} rand={rand} />;
   8 | }
   9 |

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/new-mutability/mutate-after-useeffect-ref-access.expect.md

@@ -47,7 +47,7 @@ export const FIXTURE_ENTRYPOINT = {
 ## Logs
 
 ```
-{"kind":"CompileError","fnLoc":{"start":{"line":6,"column":0,"index":190},"end":{"line":11,"column":1,"index":363},"filename":"mutate-after-useeffect-ref-access.ts"},"detail":{"options":{"category":"Refs","reason":"Cannot access refs during render","description":"React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef)","details":[{"kind":"error","loc":{"start":{"line":9,"column":2,"index":321},"end":{"line":9,"column":16,"index":335},"filename":"mutate-after-useeffect-ref-access.ts"},"message":"Cannot update ref during render"}]}}}
+{"kind":"CompileError","fnLoc":{"start":{"line":6,"column":0,"index":190},"end":{"line":11,"column":1,"index":363},"filename":"mutate-after-useeffect-ref-access.ts"},"detail":{"options":{"category":"Refs","reason":"Cannot access refs during render","description":"React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef)","details":[{"kind":"error","loc":{"start":{"line":9,"column":2,"index":321},"end":{"line":9,"column":20,"index":339},"filename":"mutate-after-useeffect-ref-access.ts"},"message":"Cannot update ref during render"}]}}}
 {"kind":"AutoDepsDecorations","fnLoc":{"start":{"line":8,"column":2,"index":269},"end":{"line":8,"column":50,"index":317},"filename":"mutate-after-useeffect-ref-access.ts"},"decorations":[{"start":{"line":8,"column":24,"index":291},"end":{"line":8,"column":30,"index":297},"filename":"mutate-after-useeffect-ref-access.ts","identifierName":"arrRef"}]}
 {"kind":"CompileSuccess","fnLoc":{"start":{"line":6,"column":0,"index":190},"end":{"line":11,"column":1,"index":363},"filename":"mutate-after-useeffect-ref-access.ts"},"fnName":"Component","memoSlots":0,"memoBlocks":0,"memoValues":0,"prunedMemoBlocks":0,"prunedMemoValues":0}
 ```

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/pass-ref-to-function.expect.md

@@ -0,0 +1,45 @@
+
+## Input
+
+```javascript
+// @validateRefAccessDuringRender
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses a ref during render. The return type of foo() is unknown.
+ */
+function Component(props) {
+  const ref = useRef(null);
+  const x = foo(ref);
+  return x.current;
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @validateRefAccessDuringRender
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses a ref during render. The return type of foo() is unknown.
+ */
+function Component(props) {
+  const $ = _c(1);
+  const ref = useRef(null);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = foo(ref);
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  const x = t0;
+  return x.current;
+}
+
+```
+      
+### Eval output
+(kind: exception) Fixture not implemented

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/pass-ref-to-function.js

@@ -0,0 +1,11 @@
+// @validateRefAccessDuringRender
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses a ref during render. The return type of foo() is unknown.
+ */
+function Component(props) {
+  const ref = useRef(null);
+  const x = foo(ref);
+  return x.current;
+}

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/preserve-memo-validation/error.maybe-mutable-ref-not-preserved.expect.md

@@ -1,42 +0,0 @@
-
-## Input
-
-```javascript
-// @validatePreserveExistingMemoizationGuarantees:true
-
-import {useRef, useMemo} from 'react';
-import {makeArray} from 'shared-runtime';
-
-function useFoo() {
-  const r = useRef();
-  return useMemo(() => makeArray(r), []);
-}
-
-export const FIXTURE_ENTRYPOINT = {
-  fn: useFoo,
-  params: [],
-};
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-error.maybe-mutable-ref-not-preserved.ts:8:33
-   6 | function useFoo() {
-   7 |   const r = useRef();
->  8 |   return useMemo(() => makeArray(r), []);
-     |                                  ^ Passing a ref to a function may read its value during render
-   9 | }
-  10 |
-  11 | export const FIXTURE_ENTRYPOINT = {
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/preserve-memo-validation/error.useMemo-with-refs.flow.expect.md

@@ -1,37 +0,0 @@
-
-## Input
-
-```javascript
-// @flow @validatePreserveExistingMemoizationGuarantees
-import {identity} from 'shared-runtime';
-
-component Component(disableLocalRef, ref) {
-  const localRef = useFooRef();
-  const mergedRef = useMemo(() => {
-    return disableLocalRef ? ref : identity(ref, localRef);
-  }, [disableLocalRef, ref, localRef]);
-  return <div ref={mergedRef} />;
-}
-
-```
-
-
-## Error
-
-```
-Found 1 error:
-
-Error: Cannot access refs during render
-
-React refs are values that are not needed for rendering. Refs should only be accessed outside of render, such as in event handlers or effects. Accessing a ref value (the `current` property) during render can cause your component not to update as expected (https://react.dev/reference/react/useRef).
-
-   5 |   const localRef = useFooRef();
-   6 |   const mergedRef = useMemo(() => {
->  7 |     return disableLocalRef ? ref : identity(ref, localRef);
-     |                                             ^^^ Passing a ref to a function may read its value during render
-   8 |   }, [disableLocalRef, ref, localRef]);
-   9 |   return <div ref={mergedRef} />;
-  10 | }
-```
-          
-      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/preserve-memo-validation/maybe-mutable-ref-not-preserved.expect.md

@@ -0,0 +1,59 @@
+
+## Input
+
+```javascript
+// @validatePreserveExistingMemoizationGuarantees:true
+
+import {useRef, useMemo} from 'react';
+import {makeArray} from 'shared-runtime';
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
+function useFoo() {
+  const r = useRef();
+  return useMemo(() => makeArray(r), []);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @validatePreserveExistingMemoizationGuarantees:true
+
+import { useRef, useMemo } from "react";
+import { makeArray } from "shared-runtime";
+
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
+function useFoo() {
+  const $ = _c(1);
+  const r = useRef();
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = makeArray(r);
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: useFoo,
+  params: [],
+};
+
+```
+      
+### Eval output
+(kind: ok) [{}]

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/preserve-memo-validation/maybe-mutable-ref-not-preserved.ts

@@ -3,6 +3,10 @@
 import {useRef, useMemo} from 'react';
 import {makeArray} from 'shared-runtime';
 
+/**
+ * Allowed: we don't have sufficient type information to be sure that
+ * this accesses an impure value during render.
+ */
 function useFoo() {
   const r = useRef();
   return useMemo(() => makeArray(r), []);

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/preserve-memo-validation/useMemo-with-refs.flow.expect.md

@@ -0,0 +1,52 @@
+
+## Input
+
+```javascript
+// @flow @validatePreserveExistingMemoizationGuarantees
+import {identity} from 'shared-runtime';
+
+component Component(disableLocalRef, ref) {
+  const localRef = useFooRef();
+  const mergedRef = useMemo(() => {
+    return disableLocalRef ? ref : identity(ref, localRef);
+  }, [disableLocalRef, ref, localRef]);
+  return <div ref={mergedRef} />;
+}
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime";
+import { identity } from "shared-runtime";
+
+const Component = React.forwardRef(Component_withRef);
+function Component_withRef(t0, ref) {
+  const $ = _c(6);
+  const { disableLocalRef } = t0;
+  const localRef = useFooRef();
+  let t1;
+  if ($[0] !== disableLocalRef || $[1] !== localRef || $[2] !== ref) {
+    t1 = disableLocalRef ? ref : identity(ref, localRef);
+    $[0] = disableLocalRef;
+    $[1] = localRef;
+    $[2] = ref;
+    $[3] = t1;
+  } else {
+    t1 = $[3];
+  }
+  const mergedRef = t1;
+  let t2;
+  if ($[4] !== mergedRef) {
+    t2 = <div ref={mergedRef} />;
+    $[4] = mergedRef;
+    $[5] = t2;
+  } else {
+    t2 = $[5];
+  }
+  return t2;
+}
+
+```
+      

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-initialization-call-2.expect.md

@@ -0,0 +1,46 @@
+
+## Input
+
+```javascript
+//@flow
+import {useRef} from 'react';
+
+/**
+ * Allowed: we aren't sure that the ref.current value flows into the render
+ * output, so we optimistically assume it's safe
+ */
+component C() {
+  const r = useRef(null);
+  if (r.current == null) {
+    f(r);
+  }
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{}],
+};
+
+```
+
+## Code
+
+```javascript
+import { useRef } from "react";
+
+function C() {
+  const r = useRef(null);
+  if (r.current == null) {
+    f(r);
+  }
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{}],
+};
+
+```
+      
+### Eval output
+(kind: exception) f is not defined

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-initialization-call-2.js

@@ -1,6 +1,10 @@
 //@flow
 import {useRef} from 'react';
 
+/**
+ * Allowed: we aren't sure that the ref.current value flows into the render
+ * output, so we optimistically assume it's safe
+ */
 component C() {
   const r = useRef(null);
   if (r.current == null) {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-initialization-call.expect.md

@@ -0,0 +1,46 @@
+
+## Input
+
+```javascript
+//@flow
+import {useRef} from 'react';
+
+/**
+ * Allowed: we aren't sure that the ref.current value flows into the render
+ * output, so we optimistically assume it's safe
+ */
+component C() {
+  const r = useRef(null);
+  if (r.current == null) {
+    f(r.current);
+  }
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{}],
+};
+
+```
+
+## Code
+
+```javascript
+import { useRef } from "react";
+
+function C() {
+  const r = useRef(null);
+  if (r.current == null) {
+    f(r.current);
+  }
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{}],
+};
+
+```
+      
+### Eval output
+(kind: exception) f is not defined

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-initialization-call.js

@@ -1,6 +1,10 @@
 //@flow
 import {useRef} from 'react';
 
+/**
+ * Allowed: we aren't sure that the ref.current value flows into the render
+ * output, so we optimistically assume it's safe
+ */
 component C() {
   const r = useRef(null);
   if (r.current == null) {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-initialization-post-access-2.expect.md

@@ -0,0 +1,49 @@
+
+## Input
+
+```javascript
+//@flow
+import {useRef} from 'react';
+
+/**
+ * Allowed: we aren't sure that the ref.current value flows into the render
+ * output, so we optimistically assume it's safe
+ */
+component C() {
+  const r = useRef(null);
+  if (r.current == null) {
+    r.current = 1;
+  }
+  f(r.current);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{}],
+};
+
+```
+
+## Code
+
+```javascript
+import { useRef } from "react";
+
+function C() {
+  const r = useRef(null);
+  if (r.current == null) {
+    r.current = 1;
+  }
+
+  f(r.current);
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: C,
+  params: [{}],
+};
+
+```
+      
+### Eval output
+(kind: exception) f is not defined

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-initialization-post-access-2.js

@@ -1,6 +1,10 @@
 //@flow
 import {useRef} from 'react';
 
+/**
+ * Allowed: we aren't sure that the ref.current value flows into the render
+ * output, so we optimistically assume it's safe
+ */
 component C() {
   const r = useRef(null);
   if (r.current == null) {

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-value-in-custom-component-event-handler-wrapper.expect.md

@@ -0,0 +1,121 @@
+
+## Input
+
+```javascript
+// @enableInferEventHandlers
+import {useRef} from 'react';
+
+// Simulates a custom component wrapper
+function CustomForm({onSubmit, children}: any) {
+  return <form onSubmit={onSubmit}>{children}</form>;
+}
+
+// Simulates react-hook-form's handleSubmit
+function handleSubmit<T>(callback: (data: T) => void) {
+  return (event: any) => {
+    event.preventDefault();
+    callback({} as T);
+  };
+}
+
+function Component() {
+  const ref = useRef<HTMLInputElement>(null);
+
+  const onSubmit = (data: any) => {
+    // Allowed: we aren't sure that the ref.current value flows into the render
+    // output, so we optimistically assume it's safe
+    if (ref.current !== null) {
+      console.log(ref.current.value);
+    }
+  };
+
+  return (
+    <>
+      <input ref={ref} />
+      <CustomForm onSubmit={handleSubmit(onSubmit)}>
+        <button type="submit">Submit</button>
+      </CustomForm>
+    </>
+  );
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @enableInferEventHandlers
+import { useRef } from "react";
+
+// Simulates a custom component wrapper
+function CustomForm(t0) {
+  const $ = _c(3);
+  const { onSubmit, children } = t0;
+  let t1;
+  if ($[0] !== children || $[1] !== onSubmit) {
+    t1 = <form onSubmit={onSubmit}>{children}</form>;
+    $[0] = children;
+    $[1] = onSubmit;
+    $[2] = t1;
+  } else {
+    t1 = $[2];
+  }
+  return t1;
+}
+
+// Simulates react-hook-form's handleSubmit
+function handleSubmit(callback) {
+  const $ = _c(2);
+  let t0;
+  if ($[0] !== callback) {
+    t0 = (event) => {
+      event.preventDefault();
+      callback({} as T);
+    };
+    $[0] = callback;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  return t0;
+}
+
+function Component() {
+  const $ = _c(1);
+  const ref = useRef(null);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    const onSubmit = (data) => {
+      if (ref.current !== null) {
+        console.log(ref.current.value);
+      }
+    };
+    t0 = (
+      <>
+        <input ref={ref} />
+        <CustomForm onSubmit={handleSubmit(onSubmit)}>
+          <button type="submit">Submit</button>
+        </CustomForm>
+      </>
+    );
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+      
+### Eval output
+(kind: ok) <input><form><button type="submit">Submit</button></form>

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-value-in-custom-component-event-handler-wrapper.tsx

@@ -18,8 +18,8 @@ function Component() {
   const ref = useRef<HTMLInputElement>(null);
 
   const onSubmit = (data: any) => {
-    // This should error: passing function with ref access to custom component
-    // event handler, even though it would be safe on a native <form>
+    // Allowed: we aren't sure that the ref.current value flows into the render
+    // output, so we optimistically assume it's safe
     if (ref.current !== null) {
       console.log(ref.current.value);
     }

compiler/packages/babel-plugin-react-compiler/src/__tests__/fixtures/compiler/ref-value-in-event-handler-wrapper.expect.md

@@ -0,0 +1,83 @@
+
+## Input
+
+```javascript
+// @enableInferEventHandlers
+import {useRef} from 'react';
+
+// Simulates a handler wrapper
+function handleClick(value: any) {
+  return () => {
+    console.log(value);
+  };
+}
+
+function Component() {
+  const ref = useRef(null);
+
+  // Allowed: we aren't sure that the ref.current value flows into the render
+  // output, so we optimistically assume it's safe
+  return (
+    <>
+      <input ref={ref} />
+      <button onClick={handleClick(ref.current)}>Click</button>
+    </>
+  );
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+
+## Code
+
+```javascript
+import { c as _c } from "react/compiler-runtime"; // @enableInferEventHandlers
+import { useRef } from "react";
+
+// Simulates a handler wrapper
+function handleClick(value) {
+  const $ = _c(2);
+  let t0;
+  if ($[0] !== value) {
+    t0 = () => {
+      console.log(value);
+    };
+    $[0] = value;
+    $[1] = t0;
+  } else {
+    t0 = $[1];
+  }
+  return t0;
+}
+
+function Component() {
+  const $ = _c(1);
+  const ref = useRef(null);
+  let t0;
+  if ($[0] === Symbol.for("react.memo_cache_sentinel")) {
+    t0 = (
+      <>
+        <input ref={ref} />
+        <button onClick={handleClick(ref.current)}>Click</button>
+      </>
+    );
+    $[0] = t0;
+  } else {
+    t0 = $[0];
+  }
+  return t0;
+}
+
+export const FIXTURE_ENTRYPOINT = {
+  fn: Component,
+  params: [{}],
+};
+
+```
+      
+### Eval output
+(kind: ok) <input><button>Click</button>