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feat(transformer/typescript): implement const enum inlining and declaration removal#20508

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feat/const-enum-support
Apr 13, 2026
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feat(transformer/typescript): implement const enum inlining and declaration removal#20508
graphite-app[bot] merged 1 commit intomainfrom
feat/const-enum-support

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@Dunqing Dunqing commented Mar 18, 2026

Summary

Depends on #20602.

Closes: #6073
Closes: #11844

  • Inline const enum member accesses (Foo.Bar / Foo["Bar"]) to literal values when optimize_const_enums is enabled
  • Remove non-exported const enum declarations when all members are evaluable
  • Use exit_statements for enum removal so inlining happens before removal
  • Delete references when inlining enum member accesses for correct semantic data
  • Handle IdentifierReferenceRename for sibling enum member references in merged declarations

Test plan

  • Transform conformance tests pass (cargo run -p oxc_transform_conformance)
  • cargo test -p oxc_transformer passes
  • Babel conformance snapshot updated

@github-actions github-actions Bot added A-semantic Area - Semantic A-transformer Area - Transformer / Transpiler C-enhancement Category - New feature or request labels Mar 18, 2026
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codspeed-hq Bot commented Mar 18, 2026

Merging this PR will not alter performance

✅ 44 untouched benchmarks
⏩ 7 skipped benchmarks1


Comparing feat/const-enum-support (6a30237) with feat/const-enum-semantic (edbaf84)

Open in CodSpeed

Footnotes

  1. 7 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.

@Dunqing Dunqing changed the title feat(semantic, transformer): support const enum inlining feat(semantic,transformer): const enum support with cross-module inlining Mar 19, 2026
@Dunqing Dunqing force-pushed the feat/const-enum-support branch 9 times, most recently from feafb0c to c3ac5ed Compare March 19, 2026 14:44
@Dunqing Dunqing changed the title feat(semantic,transformer): const enum support with cross-module inlining feat(transformer): const enum inlining and optimize_enums support Mar 20, 2026
@Dunqing Dunqing force-pushed the feat/const-enum-support branch from b6b0204 to 210bcb5 Compare March 20, 2026 00:50
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Dunqing commented Mar 20, 2026


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@Dunqing Dunqing force-pushed the feat/const-enum-support branch 3 times, most recently from ae6471c to 197cc6a Compare March 21, 2026 04:39
@Dunqing Dunqing changed the base branch from main to graphite-base/20508 March 21, 2026 13:41
@Dunqing Dunqing force-pushed the feat/const-enum-support branch from 197cc6a to 805f2fc Compare March 21, 2026 13:41
@Dunqing Dunqing force-pushed the graphite-base/20508 branch from be3fd15 to eb96a1c Compare March 21, 2026 13:41
@Dunqing Dunqing changed the base branch from graphite-base/20508 to feat/const-enum-semantic March 21, 2026 13:41
@Dunqing Dunqing changed the title feat(transformer): const enum inlining and optimize_enums support feat(transformer): implement const enum inlining and declaration removal Mar 21, 2026
@Dunqing Dunqing force-pushed the feat/const-enum-semantic branch from eb96a1c to ce2f72e Compare March 23, 2026 03:07
@Dunqing Dunqing force-pushed the feat/const-enum-support branch from 805f2fc to 75d2afe Compare March 23, 2026 03:07
@Dunqing Dunqing force-pushed the feat/const-enum-semantic branch from 0e4585b to 28b9b12 Compare March 23, 2026 06:05
@Dunqing Dunqing changed the title feat(transformer): implement const enum inlining and declaration removal feat(transformer/typescript): implement const enum inlining and declaration removal Mar 23, 2026
@Dunqing Dunqing force-pushed the feat/const-enum-support branch from a4f3a5b to b2b068f Compare March 23, 2026 06:50
@Dunqing Dunqing force-pushed the feat/const-enum-semantic branch from 28b9b12 to d2f596a Compare March 23, 2026 06:50
@Dunqing Dunqing force-pushed the feat/const-enum-support branch from b2b068f to cfa7202 Compare March 23, 2026 07:17
@Dunqing Dunqing force-pushed the feat/const-enum-semantic branch from d2f596a to 0d3cb2e Compare March 23, 2026 07:17
@Dunqing Dunqing marked this pull request as ready for review March 23, 2026 07:34
@Dunqing Dunqing requested a review from overlookmotel as a code owner March 23, 2026 07:34
@Dunqing Dunqing force-pushed the feat/const-enum-semantic branch from 0d3cb2e to 5a62fdc Compare April 3, 2026 01:00
@Dunqing Dunqing force-pushed the feat/const-enum-support branch 3 times, most recently from 816f76e to 6a30237 Compare April 7, 2026 07:54
@graphite-app graphite-app Bot added the 0-merge Merge with Graphite Merge Queue label Apr 7, 2026
@graphite-app graphite-app Bot changed the base branch from feat/const-enum-semantic to graphite-base/20508 April 7, 2026 08:52
@graphite-app graphite-app Bot force-pushed the graphite-base/20508 branch from edbaf84 to 75663c0 Compare April 7, 2026 08:56
@graphite-app graphite-app Bot force-pushed the feat/const-enum-support branch from 6a30237 to 69986e0 Compare April 7, 2026 08:56
@graphite-app graphite-app Bot changed the base branch from graphite-base/20508 to main April 7, 2026 08:57
@graphite-app graphite-app Bot force-pushed the feat/const-enum-support branch from 69986e0 to 739c4ec Compare April 7, 2026 08:57
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graphite-app Bot commented Apr 9, 2026

Merge activity

  • Apr 9, 3:24 PM UTC: This pull request can not be added to the Graphite merge queue. Please try rebasing and resubmitting to merge when ready.
  • Apr 9, 3:24 PM UTC: Graphite disabled "merge when ready" on this PR due to: a merge conflict with the target branch; resolve the conflict and try again..
  • Apr 9, 3:25 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
  • Apr 13, 3:28 AM UTC: graphite-app added this pull request to the Graphite merge queue.
  • Apr 13, 3:33 AM UTC: Merged by the Graphite merge queue.

@Dunqing Dunqing force-pushed the feat/const-enum-support branch from 739c4ec to 7bd1a40 Compare April 13, 2026 03:24
…ration removal (#20508)

## Summary

Depends on #20602.

Closes: #6073
Closes: #11844

- Inline const enum member accesses (`Foo.Bar` / `Foo["Bar"]`) to literal values when `optimize_const_enums` is enabled
- Remove non-exported const enum declarations when all members are evaluable
- Use `exit_statements` for enum removal so inlining happens before removal
- Delete references when inlining enum member accesses for correct semantic data
- Handle `IdentifierReferenceRename` for sibling enum member references in merged declarations

## Test plan

- [x] Transform conformance tests pass (`cargo run -p oxc_transform_conformance`)
- [x] `cargo test -p oxc_transformer` passes
- [x] Babel conformance snapshot updated
@graphite-app graphite-app Bot force-pushed the feat/const-enum-support branch from 7bd1a40 to 679f57f Compare April 13, 2026 03:29
@graphite-app graphite-app Bot merged commit 679f57f into main Apr 13, 2026
26 checks passed
@graphite-app graphite-app Bot deleted the feat/const-enum-support branch April 13, 2026 03:33
@graphite-app graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Apr 13, 2026
graphite-app Bot pushed a commit that referenced this pull request Apr 13, 2026
… enum inlining (#20539)

This is required in Rolldown to align with `esbuild`, which could inline a regular enum as long as all its enum members can be evaluated. See rolldown/rolldown#8796
## Summary

Depends on #20508.

- Add `optimize_enums` option to `TypeScriptOptions` that treats regular enums with all-evaluable members the same as const enums: inlines member accesses and removes non-exported declarations
- Regular enums are only removed when no runtime value references remain (e.g., `typeof Foo`, passing as argument)
- Includes 14 conformance test fixtures covering basic, string values, binary expressions, cross-member/cross-enum references, merged enums, exported (kept), non-evaluable (kept), template literals, unary expressions, typeof/value-usage/passed-as-argument (kept), and re-exported (kept)

## Test plan

- [x] 14 new conformance test fixtures under `optimize-enums/`
- [x] `cargo run -p oxc_transform_conformance` passes
- [x] `cargo test -p oxc_transformer` passes
camc314 pushed a commit that referenced this pull request Apr 13, 2026
### 💥 BREAKING CHANGES

- 36cdc31 str: [**BREAKING**] Remove identity `FromIn` impl for `Ident`
(#21251) (overlookmotel)
- 382958a span: [**BREAKING**] Remove re-exports of string types from
`oxc_span` crate (#21246) (overlookmotel)
- c4aedfa str: [**BREAKING**] Add `static_ident!` macro (#21245)
(overlookmotel)

### 🚀 Features

- e7e1aea transformer/typescript: Add `optimize_enums` option for
regular enum inlining (#20539) (Dunqing)
- 679f57f transformer/typescript: Implement const enum inlining and
declaration removal (#20508) (Dunqing)
- 6dd061c semantic: Extend `MemberWriteTarget` to cover all property
modification patterns (#21205) (Dunqing)
- f134e24 minifier: Support `property_write_side_effects` option to drop
unused property assignments (#20773) (Dunqing)
- 75663c0 semantic: Add enum member value evaluation for const enum
support (#20602) (Dunqing)
- 3cfe8ed semantic: Add `MemberWriteTarget` flag to `ReferenceFlags`
(#20772) (Dunqing)

### 🐛 Bug Fixes

- af1a586 transformer/class-properties: Use correct property name when
converting parameter properties (#21268) (Amal Jossy)
- b43250a allocator: Move allocation tracking into `Bump` (#21342)
(overlookmotel)
- 36f505f allocator: `StringBuilder` use `Allocator::alloc_layout`
(#21340) (overlookmotel)
- 7a08a6f allocator: Fix allocation counting in
`Allocator::alloc_concat_strs_array` (#21336) (overlookmotel)
- 2338e28 ecmascript: Treat `this` as potentially having side effects
(#21297) (sapphi-red)
- bd8bd39 allocator: Remove unsafe hacks from `from_raw_parts` methods
(#21283) (overlookmotel)
- 8f4c340 allocator: Remove dangerous pointer const to mut cast (#21279)
(overlookmotel)
- aa9259f parser: Add missing error code for optional param diagnostic
(#21258) (camc314)
- 04b3c2f str: Fix unsound casting const pointers to mut pointers
(#21242) (overlookmotel)
- ceadf6c str: Make `Ident::from_raw` an unsafe function (#21241)
(overlookmotel)
- eab13b3 transformer/decorators: Avoid accessor storage name collisions
(#21106) (Dunqing)
- 07e8a30 transformer/react-refresh: Handle parenthesized variable
initializers (#21047) (camc314)

### ⚡ Performance

- c3ca6f6 allocator: `StringBuilder::from_strs_array_in` check for 0
length earlier (#21338) (overlookmotel)
- c2422bb allocator: `Allocator::alloc_concat_strs_array` check for 0
length earlier (#21337) (overlookmotel)
- 04b0fdc allocator: Mark `Allocator::alloc_layout` as
`#[inline(always)]` (#21335) (overlookmotel)
- 17aee9e allocator: Use `offset_from_unsigned` in
`ChunkFooter::as_raw_parts` (#21280) (overlookmotel)
- 61adedd minifier: Fix O(n²) perf on very many var decls (#21062)
(Gunnlaugur Thor Briem)
- addcd02 napi/parser, linter/plugins: Raw transfer deserializer for
`Vec`s use shift instead of multiply where possible (#21142)
(overlookmotel)
- 3068ded napi/parser, linter/plugins: Shift before add when calculating
positions in raw transfer deserializer (#21141) (overlookmotel)
- eb400b8 napi/parser, linter/plugins: Remove `uint32` buffer view
(#21140) (overlookmotel)
- 2675085 napi/parser: Lazy deserialization use only `Int32Array`
(#21139) (overlookmotel)
- 5b35a53 napi/parser: Deserializing tokens use only `int32` array
(#21138) (overlookmotel)
- f163d10 parser: Tokens raw deserialization use `Int32Array` (#21137)
(overlookmotel)
- 7a86613 linter/plugins: Use `Int32Array`s for tokens and comments
buffers (#21136) (overlookmotel)
- 8c51121 napi/parser, linter/plugins: Raw transfer deserialize `Span`
fields as `i32`s (#21135) (overlookmotel)
- bc1bcdd napi/parser, linter/plugins: Inline trivial raw transfer field
deserializers into node object definitions (#21134) (overlookmotel)
- c0278ab napi/parser, linter/plugins: Use `Int32Array` in raw transfer
deserializer (#21132) (overlookmotel)
- 43482c7 linter/plugins: Use `>>` not `>>>` in binary search loops
(#21129) (overlookmotel)

### 📚 Documentation

- f5e1845 allocator: Upgrade headers in doc comments for `Bump` (#21263)
(overlookmotel)
- 2870174 allocator: Upper case `SAFETY` in comments (#21253)
(overlookmotel)
- 01bc269 str: Reformat `Ident` doc comments (#21240) (overlookmotel)
- dd47359 allocator: Add doc comments for panics and errors (#21230)
(overlookmotel)
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incorrect const enum output transformer: inline const enum

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