perf(linter/block-scoped-var): avoid `iter_all_scope_child_ids` by walking references/redeclarations scope ancestors by Dunqing · Pull Request #18335 · oxc-project/oxc

Dunqing · 2026-01-21T09:00:37Z

Get rid of iter_all_scope_child_ids usage by walking up the ancestor scope of the reference scope where it occurs to see if the ancestor scope is equal to the scope where the declaration is declared (which means the reference is referenced in the child scopes of the declaration that declared it).

For example:

function func() {
  {
    var a = 0; // this is a declaration whose scope is a block scope id
    function nested() {
      console.log(a); // `a` is a `Reference` and `Reference::scope_id()` is a `nested` function scope id
    }
  }
  console.log(a); // `a` is a `Reference` and `Reference::scope_id()` is a `func` function scope id
}

In this approach, we will walk up the scope.ancestor_scopes(Reference::scope_id) to see if we can find the scope id where the declaration is declared.

First a reference (inside nested), this reference is inside the child scopes, so no errors
Second a reference (Under func), this reference is out of the declaration scope, which would cause an error.

The previous approach collected all child scopes by calling iter_all_scope_child_ids first and then checked if Reference::scope_id was within all its child scope IDs. If not, then it was referenced outside of the declaration scope. This is very bad in cases where there are a few hundred child scopes and only a few references, which causes a huge heap allocation.

This new approach would also cause some performance hit in the opposite case mentioned above (i.e., when there are a few hundred references), but from the Benchmark we can see that this approach brought some performance improvements, so I think it is better than before.

Anyway, the PR aims to remove iter_all_scope_child_ids usage here and eliminate the whole API after all usages are removed.

Dunqing · 2026-01-21T09:00:53Z

feat(semantic)!: remove Scoping::scope_build_child_ids and all related APIs #18362
feat(oxc)!: remove CompilerInterface::semantic_child_scope_ids #18361
refactor(minifier): turn off scope_tree_child_ids for SemanticBuilder #18241
perf(linter): turn off scope_build_child_ids for SemanticBuilder #18360
perf(linter/exhaustive-deps): simplify the logic of checking if the identifier it is a dependency of hook #18350
perf(linter/block-scoped-var): avoid iter_all_scope_child_ids by walking references/redeclarations scope ancestors #18335 👈 (View in Graphite)
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codspeed-hq · 2026-01-21T09:06:38Z

Merging this PR will improve performance by 3.21%

⚡ 1 improved benchmark
✅ 3 untouched benchmarks
⏩ 41 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
⚡	Simulation	`linter[react.development.js]`	19.7 ms	19.1 ms	+3.21%

_{Comparing 01-21-refactor_linter_block-scoped-var_avoid_iter_all_scope_child_ids_by_walking_references_redeclarations_scope_ancestors (b5802c6) with main (5985141)²}

41 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. ↩
No successful run was found on main (8f7c57c) during the generation of this report, so 5985141 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

Dunqing · 2026-01-22T03:01:36Z

overlookmotel said he is interested in the change on iter_all_scope_child_ids, so I assigned it to him.

Copilot

Pull request overview

This PR optimizes the block-scoped-var linter rule's performance by replacing the expensive iter_all_scope_child_ids approach with a more efficient ancestor-walking algorithm. Instead of collecting all child scopes and checking membership, the new implementation walks up the scope chain from each reference to determine if it's within the declaration's scope.

Changes:

Replaced iter_all_scope_child_ids with scope_ancestors for checking scope containment
Added early exit optimization for top-level scope declarations
Added early returns when there are no references or redeclarations to check
Introduced check_if_has_reference_outside_scope helper function for the new scope checking logic

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crates/oxc_linter/src/rules/eslint/block_scoped_var.rs

graphite-app · 2026-01-22T06:24:28Z

Merge activity

Jan 22, 6:24 AM UTC: Boshen added this pull request to the Graphite merge queue.
Jan 22, 6:38 AM UTC: Merged by the Graphite merge queue.

…lking references/redeclarations scope ancestors (#18335) Get rid of `iter_all_scope_child_ids` usage by walking up the ancestor scope of the reference scope where it occurs to see if the ancestor scope is equal to the scope where the declaration is declared (which means the reference is referenced in the child scopes of the declaration that declared it). For example: ```js function func() { { var a = 0; // this is a declaration whose scope is a block scope id function nested() { console.log(a); // `a` is a `Reference` and `Reference::scope_id()` is a `nested` function scope id } } console.log(a); // `a` is a `Reference` and `Reference::scope_id()` is a `func` function scope id } ``` In this approach, we will walk up the `scope.ancestor_scopes(Reference::scope_id)` to see if we can find the scope id where the declaration is declared. 1. First `a` reference (inside `nested`), this reference is inside the child scopes, so no errors 2. Second `a` reference (Under `func`), this reference is out of the declaration scope, which would cause an error. The previous approach collected all child scopes by calling `iter_all_scope_child_ids` first and then checked if `Reference::scope_id` was within all its child scope IDs. If not, then it was referenced outside of the declaration scope. This is very bad in cases where there are a few hundred child scopes and only a few references, which causes a huge heap allocation. This new approach would also cause some performance hit in the opposite case mentioned above (i.e., when there are a few hundred references), but from the Benchmark we can see that this approach brought some performance improvements, so I think it is better than before. Anyway, the PR aims to remove `iter_all_scope_child_ids` usage here and eliminate the whole API after all usages are removed.

…18360) No use case in the linter after #18350 and #18335, so turn it off.

# Oxlint ### 💥 BREAKING CHANGES - 777fc40 ast: [**BREAKING**] Add `Ident` type (#18354) (Boshen) ### 🚀 Features - 34c3ec3 linter/prefer-logical-operator-over-ternary: Implement fixer (#18545) (camc314) - 019e0aa linter/valid-typeof: Add suggestions if type is misspelled (#18543) (camchenry) - 704c8eb linter/use-isnan: Add more specific error message for equality/inequality (#18542) (camchenry) - 1e99ace linter/use-isnan: Support more `indexOf` cases and improve diagnostic messages (#18537) (camchenry) - bffd134 linter/text-encoding-identifier-case: Add `withDash` option (#18533) (camc314) - 993fd2b parser: Parse unambiguous await with better error messages (#18480) (Boshen) - b4b6247 linter/plugins: `RuleTester` support settings (#18445) (overlookmotel) - 15d69dc linter: Implement react/display-name rule (#18426) (camchenry) - 2fbceae linter: Implement rule docs and config support for rules with tuple config options. (#18372) (connorshea) - 8db0e78 linter/plugins: Handle BOMs (#18376) (overlookmotel) - 6ac09e2 linter/plugins: Support source text not being at start of buffer (#18375) (overlookmotel) - fc3c86b linter: Update 125 rules to raise errors when provided with invalid config options. (#18104) (connorshea) - 2cc6ad2 linter/plugins: Add `ecmaFeatures` to `parserOptions` (#18313) (overlookmotel) ### 🐛 Bug Fixes - 2acf568 linter/plugins: Keep `Infinity` in rule default options (#18550) (overlookmotel) - 332d2ef linter/plugins: Add `jsx` property to `parserOptions.ecmaFeatures` (#18549) (overlookmotel) - 7d9bb1b linter: Update `eslint/func-names` to error on invalid rule config options, improve docs. (#18510) (connorshea) - 9c67974 linter: Improve the jsx-a11y/no-noninteractive-tabindex rule to match original rule logic better (#17848) (connorshea) - 75e7163 vscode: Support json5 for oxfmt (#18502) (Sysix) - c205b0d ast: Remove `ThisExpression` from `TSModuleReference` (#18489) (Boshen) - c51339a oxlint/lsp: Respect code action `source.fixAll` as an alias for `source.fixAll.oxc` (#18366) (Sysix) - 3c0e9b9 oxlint/lsp: Skip dangerous fixes/suggestions for "fix all" code action and command (#18364) (Sysix) - c44c093 linter: Fix behavior of unicorn/catch-error-name to match original rule (#18209) (connorshea) - 9c65aff linter/jsx-a11y: Change `no-autofocus` autofix to suggestion (#18155) (Ben Lowery) - 235c820 linter/unicorn: Fix `prefer-array-some` autofix for `.filter().length` pattern (#18153) (Ben Lowery) - a9925dc linter: Mark fixes in `unicorn/no-null` rule as dangerous. (#18436) (connorshea) - cee29b4 linter: Remove confusing scope from `react/only-export-components` rule diagnostics. (#18434) (connorshea) - aed3669 parser: Parse HTML-like comments in unambiguous mode (#18442) (Boshen) - b8a371d linter: Fix the path used in the gitlab format output (#18165) (connorshea) - e046ea6 linter: `vue/no-lifecycle-after-await` skip looking into arrow functions (#18302) (Sysix) - a9bfbcf linter: Compatibility issue with `DiagnosticData` type in ESLint (#18396) (루밀LuMir) - 10ab424 linter: `react/no_array_index_key` continue search for other attributes (#18409) (Lonami) - 9d776d4 linter: Update `import/no-cycle` rule to error on invalid config options. (#18330) (connorshea) - c163231 linter: Update eslint/sort-imports to validate options. (#18378) (connorshea) - 79bbcff linter: Update `eslint/func-style` to error on invalid configuration options. (#18390) (connorshea) - b871235 linter/plugins: Fix identifying "use strict" directives in scope analysis (#18402) (overlookmotel) - 5985141 linter: Update `jest/prefer-lowercase-title` rule to error on invalid config options. (#18332) (connorshea) - faca4b5 linter/plugins: Tokenize `let`, `static` and `yield` as `Keyword`s (#18368) (overlookmotel) - a3914fd linter/plugins: Allow line number passed to `report` to be 1 over line count (#18341) (overlookmotel) - 88e0896 linter: Update `typescript/no-restricted-types` rule to error on invalid config options. (#18329) (connorshea) - 9eec600 linter: Update `react/jsx-fragments` rule to raise an error on invalid configuration options (#18111) (connorshea) - 0fa969d linter: Update `react/no-will-update-set-state` to error on invalid config options (#18112) (connorshea) - 70e7be4 linter: Update `import/no-unassigned-import` to raise an error when passed invalid config options. (#18108) (connorshea) - 496cac7 linter: Update `unicorn/explicit-length-check` to raise an error when passed invalid config options. (#18107) (connorshea) - 080b1ec linter: Update 5 more rules to error on invalid config options. (#18113) (connorshea) - c5d05dd linter: Update 11 rules to raise an error on invalid config options. (#18109) (connorshea) - 9e359d4 linter/plugins: Set all properties on global vars objects (#18317) (overlookmotel) - 39c7f32 linter/plugins: Set `writeable` flag on variables where defined as globals (#18316) (overlookmotel) - a570693 linter/plugins: Fix `CatchClause` scopes (#18312) (overlookmotel) - 8c98e69 linter: `vitest/prefer-describe-function-title`: Check earlier to avoid false positive (#18177) (Jovi De Croock) - 44be0eb linter/plugins: Set scope analyse settings based on source type (#18306) (overlookmotel) - b9a14fd vscode: Update package.json to restrict a few more config options. (#18270) (Connor Shea) - c1260cb vscode: Update version info formatting. (#18274) (connorshea) - 2f68dc6 vscode: Update notification for client restart to specify tool. (#18273) (connorshea) ### ⚡ Performance - dc931ba linter/no-inner-declarations: Skip scope flags lookup in modules (#18249) (overlookmotel) - 07618a7 linter: Turn off `scope_build_child_ids` for SemanticBuilder (#18360) (Dunqing) - 1aac079 linter/exhaustive-deps: Simplify the logic of checking if the identifier it is a dependency of hook (#18350) (Dunqing) - 591d522 linter/block-scoped-var: Avoid `iter_all_scope_child_ids` by walking references/redeclarations scope ancestors (#18335) (Dunqing) - 2eefd6d linter/plugins: Remove branch from token parsing (#18369) (overlookmotel) ### 📚 Documentation - 698c21d linter: Modernize docs for various React rules (#18559) (connorshea) - 314a47c linter: Clarify the `no-find-dom-node` rule with a note that the method was removed in React 19. (#18556) (connorshea) - 5eff704 linter: Update `no-inner-declarations` to fix config option docs (#18511) (connorshea) - dd5d2f6 linter: Improve diagnostic message in `valid_typeof` rule. (#18507) (connorshea) - 8ccd853 npm: Update package homepage URLs and add keywords (#18509) (Boshen) - 4958233 linter: Add missing "What it does" section in prefer-reflect-apply rule. (#18475) (connorshea) - 2fa83a4 linter: Improve the docs for import/unambiguous. (#18474) (connorshea) - 7b1505c linter: Improve docs for `oxc/only-used-in-recursion` rule. (#18473) (connorshea) - ab506d6 linter/plugins: Correct comment (#18456) (overlookmotel) - 4565c73 linter: `react/display-name`: add docs for config options (#18430) (camchenry) - b95a89f linter: Fix docs for the curly rule. (#18374) (connorshea) - f675eb4 linter: Fix the `react/only-export-components` rule docs. (#18319) (connorshea) - 704db95 linter: "no-unused-vars" extend ignored files section for svelte and astro files (#18304) (Sysix) - 3af4a88 linter: Add "Examples" headers to rules missing them (#18266) (connorshea) # Oxfmt ### 💥 BREAKING CHANGES - 777fc40 ast: [**BREAKING**] Add `Ident` type (#18354) (Boshen) ### 🚀 Features - d71c15d oxfmt: Enable tailwind sort inside xxx-in-js (#18417) (leaysgur) - 52b5003 formatter,oxfmt: Support Angular `@Component({ template, styles })` (#18324) (leaysgur) ### 🐛 Bug Fixes - 224140c oxfmt: Canonicalize `..` component in config path (#18570) (leaysgur) - 30b467e formatter: Preserve trailing comments before the semicolon in class methods without a body (#18446) (Dunqing) - c205b0d ast: Remove `ThisExpression` from `TSModuleReference` (#18489) (Boshen) - 164bbd7 formatter: Preserve trailing comments inside ternary alternate branch (#18433) (Dunqing) - 1c50800 formatter: Use HTML entity escaping for JSX attribute strings (#18385) (Boshen) - 4e156d2 formatter: Preserve parentheses for `in` expressions in arrow function block bodies (#18352) (Boshen) - 7e6c15b oxfmt: Increase Tailwind CSS test timeout for Windows CI (#18339) (Boshen) - 29966eb formatter/dead-code-removal: Handle tailwind sorting (#18321) (leaysgur) - 29f41be formatter: Only expand mapped types when newline immediately follows opening brace (#18087) (Boshen) - 2194552 formatter: Relocate leading comments for single-element union/intersection types (#18083) (Boshen) ### ⚡ Performance - 85ab400 formatter: Store `AstNodes` itself instead of `&'a AstNodes` as the `parent` field of `AstNode` (#18428) (Dunqing) - 194d384 formatter: Reduce AstNode size by 8 bytes using following_span_start (#18347) (Dunqing) - b2df8fb oxfmt: Enable tailwind plugin only for relevant parser (#18418) (leaysgur) ### 📚 Documentation - 8ccd853 npm: Update package homepage URLs and add keywords (#18509) (Boshen) Co-authored-by: Boshen <[email protected]>

github-actions bot added A-linter Area - Linter C-cleanup Category - technical debt or refactoring. Solution not expected to change behavior labels Jan 21, 2026

Dunqing mentioned this pull request Jan 21, 2026

refactor(minifier): turn off scope_tree_child_ids for SemanticBuilder #18241

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Dunqing mentioned this pull request Jan 21, 2026

perf(linter/exhaustive-deps): simplify the logic of checking if the identifier it is a dependency of hook #18350

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Dunqing changed the title ~~refactor(linter/block-scoped-var): avoid iter_all_scope_child_ids by walking references/redeclarations scope ancestors~~ perf(linter/block-scoped-var): avoid iter_all_scope_child_ids by walking references/redeclarations scope ancestors Jan 21, 2026

github-actions bot added the C-performance Category - Solution not expected to change functional behavior, only performance label Jan 21, 2026

Dunqing changed the base branch from 01-19-refactor_minifier_turn_off_scope_tree_child_ids_for_semanticbuilder to graphite-base/18335 January 21, 2026 14:02

Dunqing force-pushed the graphite-base/18335 branch from 72b0982 to 7e6c15b Compare January 21, 2026 14:02

Dunqing force-pushed the 01-21-refactor_linter_block-scoped-var_avoid_iter_all_scope_child_ids_by_walking_references_redeclarations_scope_ancestors branch from 934040d to 0b5bb74 Compare January 21, 2026 14:02

Dunqing changed the base branch from graphite-base/18335 to main January 21, 2026 14:02

This was referenced Jan 21, 2026

perf(linter): turn off scope_build_child_ids for SemanticBuilder #18360

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feat(oxc)!: remove CompilerInterface::semantic_child_scope_ids #18361

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feat(semantic)!: remove Scoping::scope_build_child_ids and all related APIs #18362

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perf(linter): turn off scope_build_child_ids for SemanticBuilder (#…

07618a7

…18360) No use case in the linter after #18350 and #18335, so turn it off.

graphite-app bot merged commit 591d522 into main Jan 22, 2026
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release(apps): oxlint v1.42.0 && oxfmt v0.27.0 #18573

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perf(linter/block-scoped-var): avoid `iter_all_scope_child_ids` by walking references/redeclarations scope ancestors#18335

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