perf(semantic): reorder ident reference strict mode check#22652
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Pull request overview
This PR micro-optimizes semantic checking for identifier references by reordering the strict-mode guard in check_identifier_reference so the identifier-name check (eval/arguments) runs before the strict-mode scope-flag lookup. This reduces overhead on the common path where identifiers are neither eval nor arguments.
Changes:
- Reordered the
&&condition to short-circuit before callingctx.strict_mode()for most identifiers. - Preserved existing behavior since both checks are side-effect free and the logic remains equivalent.
Merging this PR will not alter performance
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check_identifier_reference runs for every identifier reference during semantic, but this strict-mode early error only applies to two identifier names: arguments and eval. Given the following two reasonable assumptions: most code is strict mode, and most identifiers are not `arguments` or `eval`, checking the identifier name first makes the common path cheaper. We avoid querying the current scope’s strict-mode flags for almost every identifier reference, and only perform that lookup when the identifier could actually trigger this diagnostic. This is behavior-preserving because both sides of the condition are side-effect free; it only changes which cheap guard runs first.
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… <2 properties (#22668) ## Summary A duplicate `__proto__` entry needs at least two property definitions — empty and single-property objects can't violate the rule. JSX/TSX call sites compile to enormous numbers of single-property object literals (`<Foo prop={x}>` → `{prop: x}`), so bailing before the loop setup and `prop_name()` call skips per-call overhead for the vast majority of `ObjectExpression` nodes seen during semantic checking. ## Context The original version of this PR also reordered `check_identifier`, `check_identifier_reference`, and `check_binding_identifier` to defer expensive scope/symbol-flag loads behind a cheap name-match. While I was working on it, @camc314 shipped equivalent changes as three separate PRs (#22652, #22653, #22656). After rebasing onto `main`, only the `check_object_expression` early-exit remains as new work; the rest of the checker hot path is already covered. This single change shows no measurable delta in `cargo bench --bench semantic` against current `main` (all five files within criterion's noise threshold) — JSX/TSX-heavy benches have already been driven down by the related PRs, and the property loop on a 1-property object is a fast path already. Pushing for completeness; happy to close if the maintainers would prefer to skip a change with no benchmark signal. Verified by `cargo test -p oxc_semantic --features cfg` (72 tests) and `cargo clippy -p oxc_semantic --all-features`. AI assisted.
### 🚀 Features - e857b0c napi/minify: Expose legalComments option and result (#20370) (Boshen) - 661132d parser: More friendly error messages for rest assignment target and rest binding element (#22719) (sapphi-red) - ee659b6 transformer/legacy-decorator: Add `strictNullChecks` option for nullable-union design:type (#22266) (Kyle Cannon) ### 🐛 Bug Fixes - e1d064e transformer/class-properties: Reparent lifted private method helpers (#22716) (Cameron) - 4ac0fca minifier: Preserve `0 && (module.exports = { ... })` cjs-module-lexer hint (#22729) (Dunqing) - 40ff611 minifier: Mark peephole loop changed when dropping dead-after-throw statement (#22722) (Dunqing) - 2f7b210 codegen: Emit pife-arrow/function leading comments inside the wrap (#22720) (Dunqing) - e184f74 parser: Improve invalid `import` property access diagnostic (#22693) (camc314) - 7baed9c transformer/private-method: Clear inherited strict flags (#22508) (camc314) - a9ad27e parser: Keep annotation comments leading without preceding newline (#22711) (Dunqing) - 9ea4d64 minifier: Re-evaluate pure/no-side-effects flags after peephole inlining (#22595) (Dunqing) - 07afbb6 minifier: Drop empty-body IIFE wrapper when called with arguments (#22589) (Dunqing) - fa7c463 semantic: Correct TS enum member symbol spans (#22689) (camc314) - 26b9396 semantic: Resolve parameter decorators outside parameter scope (#22623) (camc314) - b284045 parser: Switch to module goal eagerly on `export` (#22684) (Boshen) - dfa931d semantic: Propagate unresolved auto-increment enum value instead of defaulting to 0 (#22646) (Dunqing) - 69a6ba6 transformer/legacy-decorator: Emit Array for ReadonlyArray<T> in decorator metadata (#22265) (Kyle Cannon) - e421ef0 transformer/legacy-decorator: Return runtime binding for design:type (#22640) (Dunqing) - d61e1d7 codegen: Preserve verbatim text of pure/no-side-effects comments (#22525) (Dunqing) - 702b14e minifier: Preserve IIFE structure in DCE-only mode (#22547) (Dunqing) - 917da24 parser: Apply PURE comment through member-access chains (#22566) (Dunqing) - a069b1c codegen: Preserve quotes for cjs-module-lexer equality strings (#22551) (Dunqing) ### ⚡ Performance - 2f623b0 semantic: Skip unresolved checks for re-exports (#22660) (camc314) - 0d9553d semantic: Early-exit `check_object_expression` for objects with <2 properties (#22668) (Dunqing) - d721ad9 semantic: Use direct grandparent lookup for TS type parameters (#22658) (camc314) - 0aff288 semantic: Reorder numeric literal strict mode checks (#22657) (camc314) - 4d5ddb1 semantic: Reorder binding identifier checks (#22656) (camc314) - e32acd8 semantic: Reorder identifier ambient binding check (#22653) (camc314) - 09fe178 semantic: Reorder ident reference strict mode check (#22652) (camc314) - 4b6add2 semantic: Avoid duplicate ident clone for bindings (#22663) (camc314) - 82f9662 parser: Check identifier kind before context flag (#22662) (camc314) - d7cd951 parser: Fast path identifier parsing and inline operator helpers (#22650) (Boshen) - 7b84314 semantic: Use direct byte access for numeric leading-zero check (#22642) (camc314) - 0345a31 semantic: Pre-size class elements hash map (#22618) (camc314) - 04d3065 minifier: Drop per-call buffers in try_fold_concat (#22596) (Dunqing) - 4f289f1 semantic: Resolve_references_for_current_scope without a temp Vec (#22599) (Dunqing) - e862c15 semantic: Avoid heap alloc for var hoist scope ids (#22603) (Dunqing) - 8ff8674 semantic: Early return if `excess` is `0` in `Stats::increase_by` (#22616) (camc314) - 7a4120e semantic: Pre-reserve unresolved_references using Stats::references (#22580) (Dunqing) Co-authored-by: Dunqing <[email protected]>


check_identifier_reference runs for every identifier reference during semantic, but this strict-mode early error only applies to two identifier names: arguments and eval.
Given the following two reasonable assumptions: most code is strict mode, and most identifiers are not
argumentsoreval, checking the identifier name first makes the common path cheaper. We avoid querying the current scope’s strict-mode flags for almost every identifier reference, and only perform that lookup when the identifier could actually trigger this diagnostic.This is behavior-preserving because both sides of the condition are side-effect free; it only changes which cheap guard runs first.