[compiler] Fix set-state-in-effect false negative with NewExpression default param#36107
Merged
mofeiZ merged 1 commit intofacebook:mainfrom Apr 8, 2026
Merged
[compiler] Fix set-state-in-effect false negative with NewExpression default param#36107mofeiZ merged 1 commit intofacebook:mainfrom
mofeiZ merged 1 commit intofacebook:mainfrom
Conversation
…default param
When a component function has a destructured prop with a NewExpression
default value (e.g. `{ value = new Number() }`), the compiler would
bail out during BuildHIR when trying to lower the default value via
`lowerReorderableExpression`. This caused `validateNoSetStateInEffects`
to never run, silently suppressing the set-state-in-effect diagnostic.
The fix adds a 'NewExpression' case to `isReorderableExpression`, treating
it the same as 'CallExpression' — safe to reorder when the callee and all
arguments are themselves reorderable (e.g., global identifiers and literals).
Fixes facebook#36101
Contributor
Author
|
👋 Gentle ping — just checking if this is still on the radar for review. Happy to address any feedback or rebase if needed! |
Contributor
|
Looking at this again, you're right in that we already allow for function calls (which also may be side-effectful). My main worry here is reordering across function / constructor calls, but it looks like our lowering should preserve that |
This was referenced Apr 18, 2026
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Summary
Fixes #36101
When a component function has a destructured prop with a
NewExpressiondefault value (e.g.{ value = new Number() }), the React Compiler bails out during HIR construction when trying to lower the default value vialowerReorderableExpression. This causesvalidateNoSetStateInEffectsto never run, silently suppressing theset-state-in-effectdiagnostic.Root cause:
isReorderableExpressiondid not have a case forNewExpression, so it fell through to thedefault: return falsebranch.lowerReorderableExpressionthen recorded aTodoerror and aborted compilation of the function before any validation passes ran.Fix: Add a
NewExpressioncase toisReorderableExpressionthat mirrors the existingCallExpressioncase — the expression is safe to reorder when the callee and all arguments are themselves reorderable (e.g. global identifiers and literals).How did you test this change?
Added a new compiler fixture
invalid-setState-in-useEffect-new-expression-default-paramthat reproduces the bug from the issue. The fixture verifies that theEffectSetStatediagnostic is correctly emitted for a component with aNewExpressiondefault prop value.All 1720 compiler snapshot tests pass.