# Oxc crates_v0.140.0 — oxc crates_v0.140.0

- Product: Oxc (https://whatsnew.fyi/product/oxc)
- Vendor: Oxc
- Date: 2026-07-14
- Version: crates_v0.140.0
- Original notes: https://github.com/oxc-project/oxc/releases/tag/crates_v0.140.0
- Permalink: https://whatsnew.fyi/product/oxc/releases/crates-v0.140.0

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **added** — minifier: Extract sequence expression from expressions
- **added** — minifier: Remove unreachable code after terminating statements
- **added** — data_structures: Add likely and unlikely functions
- **added** — react_compiler: Implement enableEmitHookGuards codegen
- **added** — minifier: Apply De Morgan's law to negated comparison chains in jump guards and loop tests
- **added** — minifier: Drop write-only property assignments to unused local bindings by default
- **added** — semantic: Record const enums in EnumData
- **added** — semantic: Add Scoping::set_symbol_span
- **fixed** — minifier: Keep reads of never-assigned uninitialized bindings
- **fixed** — minifier: Preserve guaranteed throws from class heritage evaluation
- **fixed** — semantic: Track ambient contexts in SemanticBuilder
- **fixed** — transformer/decorator: Scope accessor class binding
- **fixed** — semantic: Allow reserved keywords in ambient declaration types
- **fixed** — track-memory-allocations: Exclude arena chunks from Sys allocs
- **fixed** — transformer: Clear lowered namespace redeclarations
- **fixed** — semantic: Mark declared computed MethodDefinitions as type references
- **fixed** — isolated-declarations: Emit const readonly fields as types
- **fixed** — minifier: Make __proto__ write tracking execution-order independent
- **fixed** — transformer: Remove stale enum member bindings
- **fixed** — transformer: Correct symbol flags for lowered namespaces

###### 🚀 Features

- 5b20828 minifier: Extract sequence expression from expressions (#22003) (Armano)
- 616bfa2 minifier: Remove unreachable code after terminating statements (#24441) (Dunqing)
- ddab89a data_structures: Add `likely` and `unlikely` functions (#24368) (overlookmotel)
- a3a39f9 react_compiler: Implement enableEmitHookGuards codegen (#24329) (Boshen)
- b79eef7 minifier: Apply De Morgan's law to negated comparison chains in jump guards and loop tests (#24279) (Dunqing)
- 34ff7b4 minifier: Drop write-only property assignments to unused local bindings by default (#24112) (Dunqing)
- 1b829d8 semantic: Record const enums in EnumData (#24268) (Dunqing)
- ba0944c semantic: Add `Scoping::set_symbol_span` (#24221) (camc314)

###### 🐛 Bug Fixes

- edf781d minifier: Keep reads of never-assigned uninitialized bindings (#24452) (Dunqing)
- 7d33363 minifier: Preserve guaranteed throws from class heritage evaluation (#24349) (Dunqing)
- 058a62f semantic: Track ambient contexts in `SemanticBuilder` (#24327) (camc314)
- 721eb0b transformer/decorator: Scope accessor class binding (#24330) (camc314)
- 1ebdce3 semantic: Allow reserved keywords in ambient declaration types (#24325) (camc314)
- 460176a track-memory-allocations: Exclude arena chunks from Sys allocs (#24292) (Dunqing)
- af4922b transformer: Clear lowered namespace redeclarations (#24300) (camc314)
- ffd2765 semantic: Mark declared computed `MethodDefinition`s as type references (#24296) (camc314)
- f17514b isolated-declarations: Emit const readonly fields as types (#24288) (camc314)
- 40f769d minifier: Make `__proto__` write tracking execution-order independent (#24280) (Dunqing)
- 6371fed transformer: Remove stale enum member bindings (#24272) (camc314)
- f05dfab transformer: Correct symbol flags for lowered namespaces (#24271) (Dunqing)
- 84eeb55 transformer: Correct symbol flags for lowered enums (#24269) (Dunqing)
- c3057da transformer: Preserve generated class binding spans (#24220) (camc314)
- 8260096 transformer: Correct span for lowered namespace symbol (#24222) (camc314)
- 42d00d3 semantic: Mark declared class heritage as type references (#24237) (camc314)
- 588d997 semantic: Mark TS `PropertyDefinition`s computed fields as type references (#24233) (camc314)
- 9b95632 semantic: Mark computed method keys in `TSMethodSignature`s as type references (#24232) (camc314)

###### ⚡ Performance

- 48911ec react_compiler: Use FxHashSet for membership-only block sets (#24486) (Boshen)
- 1e3e626 react_compiler: Reduce allocations in reactive-places and mutation-aliasing passes (#24476) (Boshen)
- e86e0d8 react_compiler: Avoid copying the aliasing fixpoint's abstract state (#24117) (Marius Schulz)
- 5b26643 transformer_plugins: Dispatch global defines by trailing name (#23666) (Boshen)
- dce0f29 react_compiler: Replace all compiled functions in a single AST walk (#24403) (Boshen)
- f85f0d8 ast: Delegate inherited enum variants in clone_in and estree derives (#23555) (Boshen)
- 3ff0234 allocator: Remove `unwrap` from `ReplaceWith` (#24365) (overlookmotel)
- ab22e80 transformer: Fix Rust 1.97 performance regression (#24354) (camc314)
- b47585c parser: Use `ReplaceWith` instead of `TakeIn` (#24018) (overlookmotel)
- b227a06 minifier: Use `ReplaceWith` instead of `TakeIn` (#24017) (overlookmotel)