feat(parser): report ambient definite variable assertions by camc314 · Pull Request #23165 · oxc-project/oxc

camc314 · 2026-06-09T14:22:05Z

Summary

Report TS1255 for definite assignment assertions on ambient variable declarations.
Preserve TypeScript’s diagnostic precedence for variable declarations: initializer errors first, missing type annotation errors second, then invalid ambient context.

Details

This covers ambient variable cases from the TypeScript conformance fixture, including:

declare let v1!: number;
declare var v2!: number;

declare namespace foo {
  var v!: number;
}

Copilot

Pull request overview

Adds TypeScript parser diagnostics to match tsc behavior by reporting TS1255 when a definite assignment assertion (!) is used on ambient variable declarations, and updates the parser coverage snapshot accordingly.

Changes:

Emit TS(1255) for definite assignment assertions on variable declarators in ambient contexts (declare ... / .d.ts / ambient namespace/module bodies).
Update TypeScript parser coverage snapshot to include the newly reported diagnostics.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
tasks/coverage/snapshots/parser_typescript.snap	Updates snapshot output to include TS(1255) diagnostics for ambient definite assignment assertions.
crates/oxc_parser/src/js/declaration.rs	Adds an ambient-context check to report `definite_assignment_assertion_not_permitted` for variable declarators using `!`.

codspeed-hq · 2026-06-09T14:29:50Z

Merging this PR will not alter performance

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 4 improved benchmarks
❌ 1 regressed benchmark
✅ 57 untouched benchmarks
⏩ 9 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Simulation	`pipeline[react.development.js]`	4.7 ms	6.5 ms	-26.93%
⚡	Simulation	`pipeline[binder.ts]`	15.1 ms	13.4 ms	+13.11%
⚡	Simulation	`pipeline[App.tsx]`	38.7 ms	34.8 ms	+11.27%
⚡	Simulation	`pipeline[RadixUIAdoptionSection.jsx]`	352.8 µs	322.4 µs	+9.42%
⚡	Simulation	`pipeline[kitchen-sink.tsx]`	130.9 ms	120.9 ms	+8.26%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing codex/parser-ambient-definite-variables (2d091c9) with main (9e19b9b)²}

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. ↩
No successful run was found on codex/parser-definite-property-contexts (7e53867) during the generation of this report, so main (9e19b9b) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Boshen · 2026-06-09T14:32:03Z

Merge activity

Jun 9, 2:32 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, 2:42 PM UTC: Boshen added this pull request to the Graphite merge queue.
Jun 9, 2:49 PM UTC: Merged by the Graphite merge queue.

camc314 · 2026-06-09T14:32:12Z

How to use the Graphite Merge Queue

Add either label to this PR to merge it via the merge queue:

0-merge - adds this PR to the back of the merge queue
hotfix - for urgent changes, fast-track this PR to the front of the merge queue

You must have a Graphite account in order to use the merge queue. Sign up using this link.

_{An organization admin has enabled the Graphite Merge Queue in this repository.} _{Please do not merge from GitHub as this will restart CI on PRs being processed by the merge queue.}

This stack of pull requests is managed by Graphite. Learn more about stacking.

## Summary - Report TS1255 for definite assignment assertions on ambient variable declarations. - Preserve TypeScript’s diagnostic precedence for variable declarations: initializer errors first, missing type annotation errors second, then invalid ambient context. ## Details This covers ambient variable cases from the TypeScript conformance fixture, including: ```ts declare let v1!: number; declare var v2!: number; declare namespace foo { var v!: number; } ```

### 💥 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>

## Summary - Report TS1255 for definite assignment assertions on ambient variable declarations. - Preserve TypeScript’s diagnostic precedence for variable declarations: initializer errors first, missing type annotation errors second, then invalid ambient context. ## Details This covers ambient variable cases from the TypeScript conformance fixture, including: ```ts declare let v1!: number; declare var v2!: number; declare namespace foo { var v!: number; } ```

### 💥 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>

github-actions Bot added the A-parser Area - Parser label Jun 9, 2026

camc314 marked this pull request as ready for review June 9, 2026 14:22

Copilot AI review requested due to automatic review settings June 9, 2026 14:23

Copilot started reviewing on behalf of camc314 June 9, 2026 14:23 View session

Copilot AI reviewed Jun 9, 2026

View reviewed changes

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

camc314 force-pushed the codex/parser-definite-property-contexts branch from 3f9c332 to c5246ff Compare June 9, 2026 14:27

camc314 force-pushed the codex/parser-definite-property-contexts branch from c5246ff to f9d90a3 Compare June 9, 2026 14:30

camc314 force-pushed the codex/parser-ambient-definite-variables branch from 2d091c9 to eb3396a Compare June 9, 2026 14:31

camc314 mentioned this pull request Jun 9, 2026

feat(parser): report invalid class definite assertions #23164

Merged

camc314 mentioned this pull request Jun 9, 2026

feat(parser): report definite property initializer errors #23160

Merged

camc314 mentioned this pull request Jun 9, 2026

perf(parser): store definite assertion offset #23167

Merged

graphite-app Bot force-pushed the codex/parser-definite-property-contexts branch from f9d90a3 to d169fcd Compare June 9, 2026 14:43

graphite-app Bot force-pushed the codex/parser-ambient-definite-variables branch from eb3396a to a7c1c9b Compare June 9, 2026 14:43

graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jun 9, 2026

Base automatically changed from codex/parser-definite-property-contexts to main June 9, 2026 14:48

graphite-app Bot merged commit a7c1c9b into main Jun 9, 2026
32 checks passed

graphite-app Bot deleted the codex/parser-ambient-definite-variables branch June 9, 2026 14:49

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

release(crates): oxc v0.136.0 #23443

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Uh oh!

feat(parser): report ambient definite variable assertions#23165

feat(parser): report ambient definite variable assertions#23165
graphite-app[bot] merged 1 commit into
mainfrom
codex/parser-ambient-definite-variables

camc314 commented Jun 9, 2026 •

edited

Loading

Uh oh!

Copilot AI left a comment

Uh oh!

codspeed-hq Bot commented Jun 9, 2026

Uh oh!

Boshen commented Jun 9, 2026 •

edited by graphite-app Bot

Loading

Uh oh!

camc314 commented Jun 9, 2026 •

edited

Loading

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Uh oh!

Uh oh!

Conversation

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

Uh oh!

Summary

Details

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

codspeed-hq Bot commented Jun 9, 2026

Merging this PR will not alter performance

Performance Changes

Footnotes

Uh oh!

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

Uh oh!

Merge activity

Uh oh!

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

Uh oh!

How to use the Graphite Merge Queue

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

camc314 commented Jun 9, 2026 •

edited

Loading

Boshen commented Jun 9, 2026 •

edited by graphite-app Bot

Loading

camc314 commented Jun 9, 2026 •

edited

Loading