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feat(parser): error JSX-like type assertions and generics in .mts/.cts#18910

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feat/jsx-like-errors-mts-cts
Feb 4, 2026
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feat(parser): error JSX-like type assertions and generics in .mts/.cts#18910
graphite-app[bot] merged 1 commit intomainfrom
feat/jsx-like-errors-mts-cts

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@Boshen Boshen commented Feb 4, 2026

Summary

Implements TS7059 and TS7060 errors for JSX-like syntax in .mts/.cts files:

  • TS7059: JSX-like type assertions (<T>value) - "Use an as expression instead"
  • TS7060: JSX-like type parameters in arrow functions (<T>() => {}) - "Add a trailing comma or explicit constraint"

Valid workarounds for TS7060:

  • <T,>() => {} (trailing comma)
  • <T extends unknown>() => {} (explicit constraint)
  • <T, U>() => {} (multiple type parameters)

Closes #15184

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Copilot AI review requested due to automatic review settings February 4, 2026 01:03
@github-actions github-actions bot added A-parser Area - Parser C-enhancement Category - New feature or request labels Feb 4, 2026
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Pull request overview

This PR implements TypeScript errors TS7059 and TS7060 for JSX-like syntax in .mts and .cts files, aligning Oxc's parser with TypeScript's behavior for ES module files.

Changes:

  • Added TS7059 error for JSX-like type assertions (<T>value) in .mts/.cts files
  • Added TS7060 error for ambiguous JSX-like type parameters in arrow functions (<T>() => {}) in .mts/.cts files
  • Updated parser to track trailing commas in type parameter lists to distinguish valid from invalid syntax

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

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File Description
crates/oxc_parser/src/diagnostics.rs Added two new diagnostic functions for TS7059 and TS7060 errors
crates/oxc_parser/src/ts/types.rs Refactored type parameter parsing to track trailing commas and return them alongside type parameters
crates/oxc_parser/src/ts/statement.rs Added file extension check to emit TS7059 error for type assertions in .mts/.cts files
crates/oxc_parser/src/js/arrow.rs Added validation logic to emit TS7060 error for ambiguous arrow function type parameters in .mts/.cts files
tasks/coverage/snapshots/parser_typescript.snap Updated test snapshot to reflect that nodeModulesForbidenSyntax.ts now correctly parses with diagnostic errors instead of failing

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codspeed-hq bot commented Feb 4, 2026 •
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CodSpeed Performance Report

Merging this PR will not alter performance

Comparing feat/jsx-like-errors-mts-cts (3229f99) with main (9561e7f)1

Summary

✅ 46 untouched benchmarks
⏩ 3 skipped benchmarks2

Footnotes

  1. No successful run was found on main (e7e72e2) during the generation of this report, so 9561e7f was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

  2. 3 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. ↩

@github-actions github-actions bot added the A-transformer Area - Transformer / Transpiler label Feb 4, 2026
@Boshen Boshen force-pushed the feat/jsx-like-errors-mts-cts branch from e082ac7 to 3229f99 Compare February 4, 2026 05:09
@Boshen Boshen added the 0-merge Merge with Graphite Merge Queue label Feb 4, 2026
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Boshen commented Feb 4, 2026 •
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@Boshen
feat(parser): error JSX-like type assertions and generics in .mts/`…
0eff6be 
….cts` (#18910)

## Summary

Implements TS7059 and TS7060 errors for JSX-like syntax in `.mts`/`.cts` files:

- **TS7059**: JSX-like type assertions (`<T>value`) - "Use an `as` expression instead"
- **TS7060**: JSX-like type parameters in arrow functions (`<T>() => {}`) - "Add a trailing comma or explicit constraint"

### Valid workarounds for TS7060:
- `<T,>() => {}` (trailing comma)
- `<T extends unknown>() => {}` (explicit constraint)
- `<T, U>() => {}` (multiple type parameters)

Closes #15184

🤖 Generated with [Claude Code](https://claude.com/claude-code)
@graphite-app graphite-app bot force-pushed the feat/jsx-like-errors-mts-cts branch from 3229f99 to 0eff6be Compare February 4, 2026 05:21
@graphite-app graphite-app bot merged commit 0eff6be into main Feb 4, 2026
22 checks passed
@graphite-app graphite-app bot deleted the feat/jsx-like-errors-mts-cts branch February 4, 2026 05:28
@graphite-app graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Feb 4, 2026
This was referenced Feb 9, 2026
Closed
Merged
camc314 added a commit that referenced this pull request Feb 10, 2026
@Boshen @camc314
release(crates): oxc v0.113.0 (#19210)
acdb40e 
### 💥 BREAKING CHANGES

- 2bf7293 mangler: [**BREAKING**] Enable `top_level` by default for
modules and commonjs (#18278) (sapphi-red)
- 48b0542 span: [**BREAKING**] SourceType::ts should set module to
unambigious (#18873) (Boshen)

### 🚀 Features

- 500d071 minifier: Local traverse ctx and generated minifier traverse
(#19106) (Boshen)
- 142a1be parser: Detect binary files with TS1490 error (#19047)
(Boshen)
- e316857 allocator/bitset: Add `Ones` iterator to `BitSet` (#19027)
(sapphi-red)
- 742ad3f minifier: Default `invalid_import_side_effects` to `false`
(#18916) (sapphi-red)
- 0eff6be parser: Error JSX-like type assertions and generics in
`.mts`/`.cts` (#18910) (Boshen)
- 18320c6 span: Store file extension in `SourceType` (#18893) (Boshen)

### 🐛 Bug Fixes

- a7514e4 isolated-declarations: Preserve const context in literal type
inference (#19178) (camc314)
- 312e756 isolated-declarations: Preserve readonly literal initializers
(#19177) (camc314)
- d0ca8d0 isolated-declarations: Skip parenthesis when inferring type
(#19176) (camc314)
- 110c300 oxc_ecmascript: `+[false]` and `+[true]` should evaluate to
`NaN` (#19174) (copilot-swe-agent)
- f32ea19 semantic: Report redeclaration error for import bindings
conflicting with value declarations (#19068) (Boshen)
- 3aeba7a semantic: Report redeclaration error for `function a() {} var
a` in module mode (#19041) (Boshen)
- 35e32c6 coverage: Match Babel's options.json inheritance for test
fixtures (#19002) (Boshen)
- 463d60d semantic: Skip TS2391 for standalone computed-name class
methods (#19025) (Boshen)
- 56c086b parser: Add modifier ordering validation (TS1029) (#19024)
(Boshen)
- 6067a49 linter/jsdoc: False positive in `check-tag-names` for `@` in
email addresses and npm scopes (#19021) (Boshen)
- b13bb70 semantic/jsdoc: Inline tags like `{@link}` break jsdoc parsing
(#19019) (Boshen)
- e3609e3 regular_expression: Preserve UnicodeEscape CharacterKind in
string literals (#18998) (Boshen)
- 57917ee parser: Parse decorators on rest parameters (#18938) (Boshen)
- 487601b napi: Disable mimalloc on Windows to fix worker_threads crash
(#18923) (Boshen)
- 1f6b193 parser: Validate TypeScript import type options (#18889)
(Boshen)
- 1663184 parser: Allow conditional types in function type parameters
(#18886) (Boshen)
- 5758046 parser: Error on property access after instantiation
expression (#18887) (Boshen)
- 5eb4a94 parser: Handle `<<` as two `<` tokens in type argument
contexts (#18885) (Boshen)

### ⚡ Performance

- ed8c054 oxc_str: Add precomputed hash to Ident for fast HashMap
lookups (#19143) (Boshen)
- d4a0867 transformer_plugins: Switch ReplaceGlobalDefines from Traverse
to VisitMut (#19146) (Boshen)
- 9eb16b3 syntax: Pack ASCII identifier tables into single bitflag table
(#19088) (Boshen)
- e7595d1 mangler: Use BitSet for exported symbols set (#19023)
(sapphi-red)
- 2537924 semantic: Optimize scope resolution with fast paths and
inlining (#19029) (Boshen)
- 69a8d85 mangler: Use BitSet for keep_names symbols set (#19028)
(sapphi-red)
- f78c525 parser: Try hybrid parsing for jsx children and closing
element/fragments (#18789) (camchenry)

Co-authored-by: camc314 <[email protected]>
@Boshen Boshen mentioned this pull request Feb 10, 2026
Closed
owjs3901 pushed a commit to owjs3901/oxc that referenced this pull request Feb 11, 2026
@Boshen @camc314 @owjs3901
release(crates): oxc v0.113.0 (oxc-project#19210)
68e76fb 
### 💥 BREAKING CHANGES

- 2bf7293 mangler: [**BREAKING**] Enable `top_level` by default for
modules and commonjs (oxc-project#18278) (sapphi-red)
- 48b0542 span: [**BREAKING**] SourceType::ts should set module to
unambigious (oxc-project#18873) (Boshen)

### 🚀 Features

- 500d071 minifier: Local traverse ctx and generated minifier traverse
(oxc-project#19106) (Boshen)
- 142a1be parser: Detect binary files with TS1490 error (oxc-project#19047)
(Boshen)
- e316857 allocator/bitset: Add `Ones` iterator to `BitSet` (oxc-project#19027)
(sapphi-red)
- 742ad3f minifier: Default `invalid_import_side_effects` to `false`
(oxc-project#18916) (sapphi-red)
- 0eff6be parser: Error JSX-like type assertions and generics in
`.mts`/`.cts` (oxc-project#18910) (Boshen)
- 18320c6 span: Store file extension in `SourceType` (oxc-project#18893) (Boshen)

### 🐛 Bug Fixes

- a7514e4 isolated-declarations: Preserve const context in literal type
inference (oxc-project#19178) (camc314)
- 312e756 isolated-declarations: Preserve readonly literal initializers
(oxc-project#19177) (camc314)
- d0ca8d0 isolated-declarations: Skip parenthesis when inferring type
(oxc-project#19176) (camc314)
- 110c300 oxc_ecmascript: `+[false]` and `+[true]` should evaluate to
`NaN` (oxc-project#19174) (copilot-swe-agent)
- f32ea19 semantic: Report redeclaration error for import bindings
conflicting with value declarations (oxc-project#19068) (Boshen)
- 3aeba7a semantic: Report redeclaration error for `function a() {} var
a` in module mode (oxc-project#19041) (Boshen)
- 35e32c6 coverage: Match Babel's options.json inheritance for test
fixtures (oxc-project#19002) (Boshen)
- 463d60d semantic: Skip TS2391 for standalone computed-name class
methods (oxc-project#19025) (Boshen)
- 56c086b parser: Add modifier ordering validation (TS1029) (oxc-project#19024)
(Boshen)
- 6067a49 linter/jsdoc: False positive in `check-tag-names` for `@` in
email addresses and npm scopes (oxc-project#19021) (Boshen)
- b13bb70 semantic/jsdoc: Inline tags like `{@link}` break jsdoc parsing
(oxc-project#19019) (Boshen)
- e3609e3 regular_expression: Preserve UnicodeEscape CharacterKind in
string literals (oxc-project#18998) (Boshen)
- 57917ee parser: Parse decorators on rest parameters (oxc-project#18938) (Boshen)
- 487601b napi: Disable mimalloc on Windows to fix worker_threads crash
(oxc-project#18923) (Boshen)
- 1f6b193 parser: Validate TypeScript import type options (oxc-project#18889)
(Boshen)
- 1663184 parser: Allow conditional types in function type parameters
(oxc-project#18886) (Boshen)
- 5758046 parser: Error on property access after instantiation
expression (oxc-project#18887) (Boshen)
- 5eb4a94 parser: Handle `<<` as two `<` tokens in type argument
contexts (oxc-project#18885) (Boshen)

### ⚡ Performance

- ed8c054 oxc_str: Add precomputed hash to Ident for fast HashMap
lookups (oxc-project#19143) (Boshen)
- d4a0867 transformer_plugins: Switch ReplaceGlobalDefines from Traverse
to VisitMut (oxc-project#19146) (Boshen)
- 9eb16b3 syntax: Pack ASCII identifier tables into single bitflag table
(oxc-project#19088) (Boshen)
- e7595d1 mangler: Use BitSet for exported symbols set (oxc-project#19023)
(sapphi-red)
- 2537924 semantic: Optimize scope resolution with fast paths and
inlining (oxc-project#19029) (Boshen)
- 69a8d85 mangler: Use BitSet for keep_names symbols set (oxc-project#19028)
(sapphi-red)
- f78c525 parser: Try hybrid parsing for jsx children and closing
element/fragments (oxc-project#18789) (camchenry)

Co-authored-by: camc314 <[email protected]>
OskarLebuda pushed a commit to OskarLebuda/oxc that referenced this pull request Feb 17, 2026
@Boshen @camc314 @OskarLebuda
release(crates): oxc v0.113.0 (oxc-project#19210)
ea5f1e2 
### 💥 BREAKING CHANGES

- 2bf7293 mangler: [**BREAKING**] Enable `top_level` by default for
modules and commonjs (oxc-project#18278) (sapphi-red)
- 48b0542 span: [**BREAKING**] SourceType::ts should set module to
unambigious (oxc-project#18873) (Boshen)

### 🚀 Features

- 500d071 minifier: Local traverse ctx and generated minifier traverse
(oxc-project#19106) (Boshen)
- 142a1be parser: Detect binary files with TS1490 error (oxc-project#19047)
(Boshen)
- e316857 allocator/bitset: Add `Ones` iterator to `BitSet` (oxc-project#19027)
(sapphi-red)
- 742ad3f minifier: Default `invalid_import_side_effects` to `false`
(oxc-project#18916) (sapphi-red)
- 0eff6be parser: Error JSX-like type assertions and generics in
`.mts`/`.cts` (oxc-project#18910) (Boshen)
- 18320c6 span: Store file extension in `SourceType` (oxc-project#18893) (Boshen)

### 🐛 Bug Fixes

- a7514e4 isolated-declarations: Preserve const context in literal type
inference (oxc-project#19178) (camc314)
- 312e756 isolated-declarations: Preserve readonly literal initializers
(oxc-project#19177) (camc314)
- d0ca8d0 isolated-declarations: Skip parenthesis when inferring type
(oxc-project#19176) (camc314)
- 110c300 oxc_ecmascript: `+[false]` and `+[true]` should evaluate to
`NaN` (oxc-project#19174) (copilot-swe-agent)
- f32ea19 semantic: Report redeclaration error for import bindings
conflicting with value declarations (oxc-project#19068) (Boshen)
- 3aeba7a semantic: Report redeclaration error for `function a() {} var
a` in module mode (oxc-project#19041) (Boshen)
- 35e32c6 coverage: Match Babel's options.json inheritance for test
fixtures (oxc-project#19002) (Boshen)
- 463d60d semantic: Skip TS2391 for standalone computed-name class
methods (oxc-project#19025) (Boshen)
- 56c086b parser: Add modifier ordering validation (TS1029) (oxc-project#19024)
(Boshen)
- 6067a49 linter/jsdoc: False positive in `check-tag-names` for `@` in
email addresses and npm scopes (oxc-project#19021) (Boshen)
- b13bb70 semantic/jsdoc: Inline tags like `{@link}` break jsdoc parsing
(oxc-project#19019) (Boshen)
- e3609e3 regular_expression: Preserve UnicodeEscape CharacterKind in
string literals (oxc-project#18998) (Boshen)
- 57917ee parser: Parse decorators on rest parameters (oxc-project#18938) (Boshen)
- 487601b napi: Disable mimalloc on Windows to fix worker_threads crash
(oxc-project#18923) (Boshen)
- 1f6b193 parser: Validate TypeScript import type options (oxc-project#18889)
(Boshen)
- 1663184 parser: Allow conditional types in function type parameters
(oxc-project#18886) (Boshen)
- 5758046 parser: Error on property access after instantiation
expression (oxc-project#18887) (Boshen)
- 5eb4a94 parser: Handle `<<` as two `<` tokens in type argument
contexts (oxc-project#18885) (Boshen)

### ⚡ Performance

- ed8c054 oxc_str: Add precomputed hash to Ident for fast HashMap
lookups (oxc-project#19143) (Boshen)
- d4a0867 transformer_plugins: Switch ReplaceGlobalDefines from Traverse
to VisitMut (oxc-project#19146) (Boshen)
- 9eb16b3 syntax: Pack ASCII identifier tables into single bitflag table
(oxc-project#19088) (Boshen)
- e7595d1 mangler: Use BitSet for exported symbols set (oxc-project#19023)
(sapphi-red)
- 2537924 semantic: Optimize scope resolution with fast paths and
inlining (oxc-project#19029) (Boshen)
- 69a8d85 mangler: Use BitSet for keep_names symbols set (oxc-project#19028)
(sapphi-red)
- f78c525 parser: Try hybrid parsing for jsx children and closing
element/fragments (oxc-project#18789) (camchenry)

Co-authored-by: camc314 <[email protected]>
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parser: error JSX-like type assertions and JSX-looking generics in .mts / .cts

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