[compiler] Count loop reassignments as the enclosing scope reassignin…

Commit 0ca9d20 authored [compiler] Count loop reassignments as the enclosing scope reassigning the variable (#36732) A counter initialized before a memo scope and incremented inside it (`a++` or `a = a + 1` in a `for` body) was emitted as a scope *dependency*, compared at its pre-loop value (constant every render) while the cache stored its post-loop value. The memo could never hit, so the scope recomputed on every render. Root cause: the phi-union rule in `InferReactiveScopeVariables.findDisjointMutableValues` only unioned a phi into the scope when the phi value was mutated after creation, which range-extension only does for object mutation. Primitive reassignments around a loop back-edge never extend ranges, so the counter's SSA versions stayed outside the scope and downstream dependency propagation classified the pre-loop read as a dep. The fix unions a phi with its operands and declaration when any operand is defined at or after the phi's block, i.e. the value is reassigned around a loop back-edge. This matches the shape the compiler already produced for non-primitive loop reassignment (`x = [...x, i]`). Implemented identically in the TypeScript compiler and the Rust port. Both `a++` and `a = a + 1` variants are pinned by fixtures; the first commit documents the previously-wrong codegen, the second fixes it (counter becomes a scope output, dep on `count` only). Corpus delta beyond the new fixtures is 4 fixtures, all strict improvements with byte-identical eval output: `for-in-statement-break`, `for-in-statement-continue`, `for-in-statement-type-inference` (loops previously re-ran every render, now memoized), and `sequence-expression` (two memo blocks collapse into one). Known limitation, unchanged from before: conditional reassignment in a loop (`for (...) { if (c) a++; }`) routes through a join phi that this rule cannot see; that shape behaves as it did before this change. Verification: TS snap 1806/1806, Rust snap 1806/1806, cargo workspace green, scoped TS-vs-Rust HIR parity harness green. Closes #349711 parent 77df6e1 commit 0ca9d20 10 files changed Lines changed: 238 additions & 45 deletions File tree - compiler - crates/react_compiler_inference/src - packages/babel-plugin-react-compiler/src - ReactiveScopes - __tests__/fixtures/compiler Lines changed: 20 additions & 1 deletion | Original file line number | Diff line number | Diff line change | | |---|---|---|---| | ||| 284 | 284 | | | 285 | 285 | | | 286 | 286 | | | 287 | | - | | | 287 | + | | | 288 | + | | | 289 | + | | | 290 | + | | | 291 | + | | | 292 | + | | | 293 | + | | | 294 | + | | | 295 | + | | | 296 | + | | | 297 | + | | | 298 | + | | | 299 | + | | | 300 | + | | | 301 | + | | | 302 | + | | | 303 | + | | | 304 | + | | | 305 | + | | | 306 | + | | 288 | 307 | | | 289 | 308 | | | 290 | 309 | | | | Lines changed: 24 additions & 5 deletions | Original file line number | Diff line number | Diff line change | | |---|---|---|---| | ||| 25 | 25 | | | 26 | 26 | | | 27 | 27 | | | 28 | | - | | | 28 | + | | 29 | 29 | | | 30 | 30 | | | 31 | 31 | | | | ||| 287 | 287 | | | 288 | 288 | | | 289 | 289 | | | 290 | | - 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