fix(react_compiler): drop stray empty statement from catch bindings by Boshen · Pull Request #24133 · oxc-project/oxc

Boshen · 2026-07-03T16:49:19Z

Root cause

A try/catch with a catch parameter lowers the catch binding to a DeclareLocal (and a StoreLocal in the handler) with InstructionKind::Catch. In emit_store these codegen to an empty statement — a faithful port of the fork's emitStore (case InstructionKind.Catch: return t.emptyStatement()) — because the catch parameter itself is emitted separately, from the Try terminal's handler_binding, so the declaration has no textual form.

oxc's other instruction paths drop such empty statements (ox_codegen_instruction_nullable filters EmptyStatement -> None), but the StoreLocal/DeclareLocal/DeclareContext/Destructure path returned the result of ox_codegen_store_or_declare directly, so the catch declaration's empty statement was pushed into the block. It surfaced as a stray ;:

bb0: {
  x = [];
  ;          // <- stray, from the catch `DeclareLocal`
  try { ... } catch (t1) { ... }
}

and, when the try was optimized away entirely, as a bare ; in the function body (let x; ; return 42;). The reference goldens (*.expect.md) never contain such a ;.

Fix

crates/oxc_react_compiler/src/react_compiler_reactive_scopes/codegen_reactive_function.rs:

Drop the empty statement from the store/declare path in ox_codegen_instruction_nullable, consistent with the other instruction paths.
Removing it turned a labeled block that wrapped only a try into a single-statement block, which tripped the labeled-block single-statement unwrap and dropped the braces (bb0: try {} instead of bb0: { try {} catch {} }). Restrict the unwrap so a labeled try keeps its braces — matching the reference output, which always brace-wraps a labeled try (the catch declaration originally padded the block to two statements). Other single statements (if/for/switch/while, nested labels such as bb1: bb2: switch) still unwrap as before.

Fixtures changed

20 snapshots updated, each removing exactly one stray ; (braces and everything else preserved). ~29 try/catch fixtures now match the fork golden at the compiled-component level. The change also cleaned two non-try-catch-named fixtures that embed a try (repro-unreachable-code-early-return-in-useMemo, error.bug-invariant-local-or-context-references). The whole-suite diff vs main is 20 files, all -1 line; no snapshot regressed.

Remaining work (out of scope, pre-existing)

The still-diverging try/catch fixtures differ only by codegen formatting / error handling unrelated to the stray ;:

Prettier-style formatting: inline vs multi-line object/array literals and FIXTURE_ENTRYPOINT params, multi-line vs inline JSX (try-catch-multiple-value-blocks, try-catch-within-object-method*), directive-comment placement (propagate-scope-deps-hir-fork__*, repro-nested-try-catch-in-usememo).
finally clauses and invalid-JSX-in-catch fixtures (error.todo*, invalid-jsx-*, fault-tolerance__error.try-finally-*) where oxc's error/## Error behavior diverges from the fork.

The catch-binding declaration (`DeclareLocal`/`StoreLocal` with `InstructionKind::Catch`) lowers to an empty statement, since the catch parameter itself is emitted from the `Try` terminal's handler binding. The store/declare codegen path returned this as `Some(EmptyStatement)`, bypassing the empty-statement filtering that the other instruction paths apply, so it surfaced as a stray `;` at the top of the labeled block wrapping every `try` (and as a bare `;` in the body when the try was optimized away). Drop the empty statement from the store/declare path. Removing it turned a labeled block wrapping only a `try` into a single-statement block, which triggered the labeled-block unwrap and dropped the braces (`bb0: try` instead of `bb0: { try {} catch {} }`); restrict that unwrap so a labeled `try` keeps its braces, matching the reference output. Other single statements (if/for/switch/while/nested labels) still unwrap. 20 snapshots updated, each removing a stray `;`.

codspeed-hq · 2026-07-03T16:57:31Z

Merging this PR will not alter performance

✅ 10 untouched benchmarks
⏩ 61 skipped benchmarks¹

_{Comparing fix/rc-try-catch (2a31e35) with main (3c1ae2e)}

61 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. ↩

### 🚀 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]>

Boshen marked this pull request as ready for review July 4, 2026 02:44

Boshen merged commit f13df97 into main Jul 4, 2026
30 checks passed

Boshen deleted the fix/rc-try-catch branch July 4, 2026 02:45

oxc-guard Bot mentioned this pull request Jul 6, 2026

release(crates): oxc v0.139.0 #24218

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fix(react_compiler): drop stray empty statement from catch bindings#24133

fix(react_compiler): drop stray empty statement from catch bindings#24133
Boshen merged 1 commit into
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fix/rc-try-catch

Boshen commented Jul 3, 2026

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codspeed-hq Bot commented Jul 3, 2026

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Boshen commented Jul 3, 2026

Root cause

Fix

Fixtures changed

Remaining work (out of scope, pre-existing)

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codspeed-hq Bot commented Jul 3, 2026

Merging this PR will not alter performance

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