[compiler] Fix incorrect closure outlining for factory-function components#36538
[compiler] Fix incorrect closure outlining for factory-function components#36538tejasupmanyu wants to merge 1 commit into
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…nents When a React component is defined inside a factory function (e.g. `makeCounter`), the compiler's `infer` compilation mode classifies factory-scope variables (e.g. `counter`) as `ModuleLocal` globals because `parentFunction.scope.parent` coincidentally matches the factory function's scope rather than the true module scope. As a result, inner callbacks that reference those variables (e.g. `getCount = () => counter.value`) end up with an empty `context` array. The `outlineFunctions` pass saw `context.length === 0` and incorrectly hoisted `getCount` to a top-level `_temp` function at module scope, where `counter` is undefined at runtime. Fix: before outlining a FunctionExpression, check whether its body contains a `LoadGlobal(ModuleLocal)` instruction for a name that does not actually exist at the true program/module scope (via `scope.getProgramParent().getBinding(name)`). If such a reference is found the function is left inline — outlined, it would capture an undefined variable. Fixes facebook#34901
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Summary
When the outermost function being compiled is nested inside another function (factory/HOC,
infermode),HIRBuilderresolves identifiers againstparentFunction.scope.parent— the enclosing function's scope, not the program scope. The enclosing scope's locals are mis-tagged asModuleLocal, andoutlineFunctionsseescontext.length === 0and hoists the inner closure to module scope, where the captured name is undefined at runtime.This PR adds a guard in
outlineFunctions: a function is not outlined if its body contains aLoadGlobal(ModuleLocal)whose name does not resolve at the program scope.Fixes #34901
Alternative considered
A more principled fix is to correct the misclassification in
HIRBuilder.resolveIdentifier/isContextIdentifierby usingscope.getProgramParent()instead ofscope.parent. That change alone is semantically correct but exposes a deeper structural gap: the compiler's capture machinery (gatherCapturedContext,captureScopes) only walks scopes up toparentFunction.scope, so factory-scope variables get no value-kind initialization andInferMutationAliasingEffectsinvariant-fails. Closing that gap requires extending capture collection up to (but excluding) the program scope and gathering captures for the outermost function as well — a substantially larger change with wide effects on how nested functions are lowered. Worth doing in a follow-up; out of scope for this fix.Test plan
factory-function-component-captures-outer-scope.js. Eval output renders<div>42</div>, confirminggetCountstays inline.yarn workspace babel-plugin-react-compiler lintclean.