perf(parser): store class definite assertion offset by camc314 · Pull Request #23170 · oxc-project/oxc

camc314 · 2026-06-09T14:58:07Z

Store class property definite assignment assertion positions as u32 offsets instead of carrying a full Span.
Reconstruct the one-character diagnostic span only when emitting class definite-assignment diagnostics.
aligns the behaviour for definite assertion errors with variables by reporting on the definite assertion rather than on the whole class member

Copilot

Pull request overview

This PR optimizes TypeScript parsing diagnostics for definite assignment assertions by storing the ! position as a compact u32 offset (instead of a full Span) and reconstructing a 1-character diagnostic span only when emitting errors, improving both memory usage and diagnostic precision.

Changes:

Store definite assignment assertion positions as u32 offsets for variable declarators and class property declarations, reconstructing Span::sized(start, 1) only when reporting diagnostics.
Update class-property definite-assignment diagnostics to point at the ! token rather than the whole class member span.
Refresh conformance/coverage snapshots to reflect the narrower (one-character) diagnostic highlights and updated column offsets.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tasks/transform_conformance/snapshots/oxc.snap.md	Updates expected diagnostic spans/columns to highlight only the `!` for class properties.
tasks/transform_conformance/snapshots/babel.snap.md	Updates expected Babel conformance snapshot output for narrower `!` diagnostic spans.
tasks/coverage/snapshots/parser_typescript.snap	Updates TypeScript parser coverage snapshots for 1-char `!` highlights and shifted columns.
tasks/coverage/snapshots/parser_babel.snap	Updates Babel parser coverage snapshots to match new `!`-only diagnostic spans.
crates/oxc_parser/src/js/declaration.rs	Stores variable definite-assertion token start offset and reconstructs a 1-char span at diagnostic time.
crates/oxc_parser/src/js/class.rs	Stores class property definite-assertion token start offset and uses it for `!`-precise diagnostics (snapshots adjusted accordingly).

codspeed-hq · 2026-06-09T15:13:55Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 9 skipped benchmarks¹

_{Comparing codex/parser-class-definite-offset (e378213) with main (a7c1c9b)}

9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

camc314 · 2026-06-09T15:32:41Z

Merge activity

Jun 9, 3:32 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jun 9, 3:32 PM UTC: camc314 added this pull request to the Graphite merge queue.
Jun 9, 3:39 PM UTC: Merged by the Graphite merge queue.

- Store class property definite assignment assertion positions as `u32` offsets instead of carrying a full `Span`. - Reconstruct the one-character diagnostic span only when emitting class definite-assignment diagnostics. - aligns the behaviour for definite assertion errors with variables by reporting on the definite assertion rather than on the whole class member

## Summary - Pass the definite-assignment assertion token offset through the class accessor-property parser path. - Report invalid ambient and abstract `accessor prop!` diagnostics on the `!` token, matching the span behavior used by variable declarators and normal class properties. - Add focused misc parser coverage for the accessor-specific invalid cases. ## Rationale This follows up #23170. That parser change already narrowed definite-assignment diagnostics for variables and normal class properties, but accessor properties still kept only a boolean. That meant `accessor prop!` could only report TS1255 using the full class element span. Carrying the offset into `parse_class_accessor_property` aligns accessor diagnostics with the other definite-assignment diagnostics and keeps the AST shape unchanged by storing only `definite.is_some()`. The misc fixture is needed because upstream TypeScript coverage exercises invalid definite assertions on normal fields, but not invalid accessor properties. Existing misc coverage only had a valid `accessor y!` pass case, so `just coverage` did not specifically protect the accessor diagnostic span this fixes.

### 💥 BREAKING CHANGES - 7a24911 codegen: [**BREAKING**] Borrow sourcemaps from codegen (#23422) (Boshen) - bb0ed44 transformer: [**BREAKING**] Disable styled-components transpileTemplateLiterals by default (#23171) (Boshen) ### 🚀 Features - 1490a0a linter/react: Implement react-compiler rule (#23202) (Boshen) - 6c0bdf0 transformer/react-refresh: Support `module.property.useHook()` (#23190) (Dunqing) - 47991bd semantic: Report TS1228 for invalid type predicates (#23174) (camc314) - 1d3af58 parser: Add TS2398 parameter property diagnostic (#23216) (camc314) - 44313da semantic: Add `scope_is_descendant_of` api (#22313) (camc314) - e5050c0 parser: Improve diagnostic for rest initializer (#23205) (camc314) - ec266bb transformer: Run React Compiler as a feature-gated transform pass (#23201) (Boshen) - e7374fe parser: Report error for `const` modifier on interface type parameter (#23173) (camc314) - a7c1c9b parser: Report ambient definite variable assertions (#23165) (camc314) - d169fcd parser: Report invalid class definite assertions (#23164) (camc314) - 00244d8 parser: Report definite property initializer errors (#23160) (camc314) ### 🐛 Bug Fixes - 52d0c31 transformer: Replace ambient dot defines (#23231) (camc314) - 2c28748 transformer/class: Parent generated constructors to class scope (#23222) (camc314) - 8edd234 parser: Report accessor definite assertion on token (#23203) (camc314) - de38a3f react_compiler: Keep imports referenced only by a local re-export (#23176) (Boshen) - f5721c2 codegen: Preserve parentheses around `intrinsic` type reference (#23156) (Boshen) - e89f81d parser: Don't emit TS1477 for parenthesized instantiation expression (#23147) (Boshen) - 8a04149 parser: Reject module-referencing imports/exports in a namespace body (#22829) (Boshen) ### ⚡ Performance - 2783295 parser: Table-driven operator precedence lookup (#23346) (Boshen) - 231d5de parser: Single-match member expression dispatch (#23347) (Boshen) - e89729b codegen: Accept one-shot wrap closures (#23265) (camc314) - a6c11fa parser: Force-inline read_non_decimal to fold per-digit number dispatch (#23157) (Boshen) - d74964c parser: Store class definite assertion offset (#23170) (camc314) - f0fda4d parser: Shrink-wrap cold diagnostic tails out of hot frames (#23159) (Boshen) - a082180 parser: Store definite assertion offset (#23167) (camc314) - 534f9c6 oxc: Conditionally rebuild semantic in compiler pipeline (#23153) (Boshen) - b435c6a parser: Skip checkpoint for `infer T extends U` constraint in disallow context (#23128) (Boshen) - 7464dce parser: Peek instead of checkpoint/rewind for `export default` modifier (#23124) (Boshen) - 80a9a32 parser: Fast-path single-keyword TS declarations (#23083) (Boshen) - da1a6c6 diagnostics: Migrate to allocation-optimized oxc-miette (#23094) (Boshen) - b7b08ce parser: Peek once for the static modifier disambiguation (#23079) (Boshen) - e7e07a3 parser: Fold unary dispatch into a single match (#23076) (Boshen) ### 📚 Documentation - d241add semantic: Add `AGENTS.md` test guidance for agents (#23441) (camc314) - 026f1ae parser: Add `AGENTS.md` test guidance for agents (#23440) (camc314) - 09755ac transformer: Add `AGENTS.md` test guidance for agents (#23439) (camc314) - e6bdfd4 lexer: Correct reference link for `byte_handlers!` (#23313) (Dunqing) - 65b6d7a allocator: Fix memory leaks in `Arena` examples (#23257) (overlookmotel) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

camc314 changed the base branch from codex/parser-definite-offset to main June 9, 2026 15:02

github-actions Bot added A-parser Area - Parser A-transformer Area - Transformer / Transpiler labels Jun 9, 2026

camc314 marked this pull request as ready for review June 9, 2026 15:03

Copilot AI review requested due to automatic review settings June 9, 2026 15:03

Copilot started reviewing on behalf of camc314 June 9, 2026 15:03 View session

Copilot AI reviewed Jun 9, 2026

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Comment thread crates/oxc_parser/src/js/class.rs

camc314 added the 0-merge Merge with Graphite Merge Queue label Jun 9, 2026

camc314 self-assigned this Jun 9, 2026

graphite-app Bot force-pushed the codex/parser-class-definite-offset branch from e378213 to d74964c Compare June 9, 2026 15:33

graphite-app Bot merged commit d74964c into main Jun 9, 2026
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graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jun 9, 2026

graphite-app Bot deleted the codex/parser-class-definite-offset branch June 9, 2026 15:39

camc314 mentioned this pull request Jun 10, 2026

fix(parser): report accessor definite assertion on token #23203

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oxc-guard Bot mentioned this pull request Jun 15, 2026

release(crates): oxc v0.136.0 #23443

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perf(parser): store class definite assertion offset#23170

perf(parser): store class definite assertion offset#23170
graphite-app[bot] merged 1 commit into
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camc314 commented Jun 9, 2026 •

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codspeed-hq Bot commented Jun 9, 2026 •

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codspeed-hq Bot commented Jun 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Merging this PR will not alter performance

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camc314 commented Jun 9, 2026 • edited by graphite-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

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camc314 commented Jun 9, 2026 •

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