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perf(transformer/decorators): narrow type earlier#23987

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Jul 2, 2026
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perf(transformer/decorators): narrow type earlier#23987
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@overlookmotel

@overlookmotel overlookmotel commented Jun 30, 2026

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Tiny optimization to decorators transformer.

Narrow PropertyKey to Expression earlier. This has 2 advantages:

  1. Proximity of match_expression!(PropertyKey) and key.to_expression_mut() makes it more likely compiler can remove the "is key an Expression?" check from to_expression_mut.
  2. Call create_uid_var_based_on_node with Expression instead of PropertyKey, which has a few less branches.

overlookmotel commented Jun 30, 2026

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codspeed-hq Bot commented Jun 30, 2026

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Merging this PR will not alter performance

✅ 52 untouched benchmarks
⏩ 19 skipped benchmarks1


Comparing om/06-27-perf_transformer_decorators_narrow_type_earlier (a3ebd6b) with main (675e6a8)

Open in CodSpeed

Footnotes

  1. 19 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.

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overlookmotel marked this pull request as ready for review July 1, 2026 08:29
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overlookmotel requested a review from Dunqing as a code owner July 1, 2026 08:29
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Pull request overview

This PR aims to micro-optimize the legacy decorators transformer by narrowing PropertyKey to Expression earlier during computed-key handling, reducing branching in to_expression_mut() and in create_uid_var_based_on_node.

Changes:

  • Replaces the computed-key catch-all arm with a match_expression!(PropertyKey) arm and narrows via key.to_expression_mut() earlier.
  • Passes an Expression reference into VarDeclarationsStore::create_uid_var_based_on_node instead of a PropertyKey.
  • Builds the mutated key directly with PropertyKey::new_assignment_expression(...) instead of creating an Expression first and converting.

Comment thread crates/oxc_transformer/src/decorator/legacy/mod.rs
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Merge activity

Tiny optimization to decorators transformer.

Narrow `PropertyKey` to `Expression` earlier. This has 2 advantages:

1. Proximity of `match_expression!(PropertyKey)` and `key.to_expression_mut()` makes it more likely compiler can remove the "is `key` an `Expression`?" check from `to_expression_mut`.
2. Call `create_uid_var_based_on_node` with `Expression` instead of `PropertyKey`, which has a few less branches.
@graphite-app
graphite-app Bot force-pushed the om/06-27-perf_transformer_decorators_narrow_type_earlier branch from a3ebd6b to 527b8e5 Compare July 2, 2026 01:31
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graphite-app Bot merged commit 527b8e5 into main Jul 2, 2026
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@graphite-app graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jul 2, 2026
@graphite-app
graphite-app Bot deleted the om/06-27-perf_transformer_decorators_narrow_type_earlier branch July 2, 2026 01:35
camc314 pushed a commit that referenced this pull request Jul 3, 2026
Tiny optimization to decorators transformer.

Narrow `PropertyKey` to `Expression` earlier. This has 2 advantages:

1. Proximity of `match_expression!(PropertyKey)` and `key.to_expression_mut()` makes it more likely compiler can remove the "is `key` an `Expression`?" check from `to_expression_mut`.
2. Call `create_uid_var_based_on_node` with `Expression` instead of `PropertyKey`, which has a few less branches.
Boshen added a commit that referenced this pull request Jul 6, 2026
### 🚀 Features

- 260425f semantic/examples: Include unresolved references (#24214)
(camc314)
- 2d9b0b3 minifier: Fold boolean-literal ternary branches in value
contexts (#24110) (Dunqing)
- 61fbf10 ast: Implement `ReplaceWith` on all AST types (#24013)
(overlookmotel)
- 7db7a29 allocator: Add `ReplaceWith` trait (#24012) (overlookmotel)
- 4eb074e mangler: Add `reserved` option for names that must not be
mangled (#24041) (Dunqing)
- 2e62012 data_structures: Add `StringExt` trait (#24006)
(overlookmotel)
- 60e7160 minifier: Drop side-effect-free IIFEs whose result is unused
(#23967) (Dunqing)
- 26dd9e2 ast: Add method to widen inherited enum ref to parent ref
(#23961) (overlookmotel)

### 🐛 Bug Fixes

- e8b50ee transformer: Clean up semantics for stripped TypeScript syntax
(#24180) (camc314)
- d966d0b react_compiler: Remove clippy allows (#24168) (Boshen)
- 854ef8d react_compiler: Compile generic functions instead of
over-bailing on type-param hoisting (#24158) (Boshen)
- 093586c react_compiler: Align memoization cache-slot allocation with
Babel (#24157) (Boshen)
- 09c8f59 react_compiler: Normalize snapshot fixture paths (#24142)
(camc314)
- f13df97 react_compiler: Drop stray empty statement from catch bindings
(#24133) (Boshen)
- cb2a505 react_compiler: Codegen destructuring reassignment targets
(#24131) (Boshen)
- b82c394 react_compiler: Propagate codegen invariants instead of
emitting empty bodies (#24128) (Boshen)
- 5771982 react_compiler: Render unchanged programs as source in fixture
snapshots (#24129) (Boshen)
- 4b16e1a transformer/async-to-generator: Preserve direct eval scope
flags (#24136) (camc314)
- 4e9194f react_compiler: Lower `delete obj.prop` to
Property/ComputedDelete (#24123) (Boshen)
- 0b25582 ast: Type binding node `typeAnnotation` as `TSTypeAnnotation |
null` (#23113) (Boshen)
- 018c0e5 transformer: Hoist lowered async declarations (#22770)
(camc314)
- 652fbaf mangler: Keep names of destructured exported bindings (#24036)
(Dunqing)
- e274415 minifier: Don't drop global calls that throw despite pure
arguments (#23917) (Dunqing)
- 59abb30 minifier: Only merge string literals in `try_fold_add` when
the inner operator is `+` (#23622) (Jerry Zhao)

### ⚡ Performance

- c5ca77b transformer: Avoid cloning refresh options (#24191) (camc314)
- bf1a151 react_compiler: Compile out debug printers (#24184) (Boshen)
- abb44a0 transformer: Build fixed object-rest arguments (#24190)
(camc314)
- a4db731 isolated_declarations: Use `ReplaceWith` instead of `TakeIn`
(#24016) (overlookmotel)
- ff10855 transformer: Use `ReplaceWith` instead of `TakeIn` (#24015)
(overlookmotel)
- bd49aff ecmascript: Avoid heap-allocating Math.min/max/imul operands
(#23941) (Lawrence Lin)
- e4b708b react_compiler: Skip compiled files before prefilters (#24171)
(Boshen)
- c59f2fe rust: Return impl ExactSizeIterator from slice-backed
accessors (#24144) (Boshen)
- 5d6d04a codegen: SWAR-skip boring byte runs in sourcemap line/column
scan (#24023) (Boshen)
- a55e0be traverse: Reduce string operations in `get_var_name_from_node`
(#24007) (overlookmotel)
- e6d48e1 transformer/nullish_coalescing: Move cold path into separate
function (#23989) (overlookmotel)
- c4e35b5 transformer/object_rest_spread: Pre-allocate capacity in `Vec`
(#23988) (overlookmotel)
- 527b8e5 transformer/decorators: Narrow type earlier (#23987)
(overlookmotel)

### 📚 Documentation

- 30d17f5 allocator: Clarify docs for `TakeIn::take_in_box` (#24093)
(overlookmotel)
- 675e6a8 ast: Correct doc comment for `PrivateFieldExpression` (#24008)
(overlookmotel)
- e4c30e6 minifier: Explain what `dce` mode means (#23994) (Dunqing)
- 37cbf88 ast_macros: Document fields of `StructDetails` (#23959)
(overlookmotel)
- 4de3e54 ast: Correct doc comment (#23948) (overlookmotel)

Co-authored-by: Boshen <[email protected]>
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