fix(parser): parse for (using of = ...) as using declaration

[Boshen]

Summary

• Fix parsing of for (using of = null;;) as a using declaration where of is the binding identifier
• Previously, the parser incorrectly treated of as the keyword starting a for-of loop

The fix uses a lookahead to check if the token after of is =, ;, or :, matching TypeScript's parser behavior.

Test plan

• cargo coverage -- parser - conformance tests pass
• cargo test -p oxc_parser - unit tests pass

🤖 Generated with Claude Code

[Boshen]

Merge activity

• Jan 17, 5:10 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Jan 18, 12:41 AM UTC: Boshen added this pull request to the Graphite merge queue.
• Jan 18, 12:48 AM UTC: Merged by the Graphite merge queue.

[Copilot]

Pull request overview

This PR fixes a parser bug where for (using of = ...) was incorrectly treated as a for-of loop instead of a using declaration with of as the binding identifier. The fix uses a lookahead to check the token after of to distinguish between the two cases.

Changes:

• Modified lookahead logic in for statement parsing to handle of as a binding identifier in using declarations
• Improved test coverage with previously failing test262 and Babel test cases now passing

Reviewed changes

Copilot reviewed 1 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/oxc_parser/src/js/statement.rs	Updated lookahead logic for using declarations to check tokens after of
tasks/coverage/snapshots/parser_test262.snap	Improved parsing success rate with using-for-statement.js now passing
tasks/coverage/snapshots/parser_babel.snap	Multiple using declaration tests now parse correctly
tasks/coverage/snapshots/parser_typescript.snap	TypeScript using declaration test now parses correctly
tasks/coverage/snapshots/semantic_test262.snap	Semantic analysis passes for newly parsed test
tasks/coverage/snapshots/semantic_babel.snap	Semantic analysis updated for newly parsed tests

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing fix/parser-using-of-for-statement (bad5823) with main (830b757)}

Summary

✅ 42 untouched benchmarks
⏩ 3 skipped benchmarks¹

Footnotes

1. 3 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. ↩