refactor(parser): remove token lookahead in type parsing

[camchenry]

• towards parser: use checkpoints instead of token lookahead #11194

Removes token lookahead in TypeScript type parsing. There was one place I had to use an additional rewind/checkpoint where the TS parser doesn't, otherwise it added extra regressions. I think this is fixable eventually, but for now I've opted to keep the conformance tests passing exactly the same.

[camchenry]

• refactor(parser): remove token lookahead in type parsing #11241 👈 (View in Graphite)
• main

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[Copilot]

Pull Request Overview

This PR refactors TypeScript type parsing by removing direct lookahead via peek_at/peek_kind and replacing it with a unified lookahead mechanism and dedicated helper functions.

• Replaced peek_at/peek_kind checks with lookahead(Self::…) calls and new is_next_token_* helpers.
• Introduced a temporary checkpoint/rewind hack to preserve conformance tests in one parsing branch.
• Updated several predicate functions (is_start_of_mapped_type, next_token_is_start_of_type, etc.) to consume tokens differently.

Comments suppressed due to low confidence (2)

crates/oxc_parser/src/ts/types.rs:537

• The initial '{' check was removed and bump_any() always consumes the current token, which breaks the original guard and alters parser state. Restore the at(Kind::LCurly) check and use lookahead to inspect tokens without consuming.

self.bump_any();

crates/oxc_parser/src/ts/types.rs:925

• Using eat here mutates parser state by consuming the ? when testing for ?:. This may advance the parser incorrectly. Replace with a lookahead or peek check to avoid side effects.

self.eat(Kind::Question) && self.at(Kind::Colon)

[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #11241 will degrade performances by 3.18%

_{Comparing 05-22-refactor_linter_remove_token_lookahead_in_type_parsing (6ddf7a8) with main (1846b03)}

Summary

❌ 1 regressions
✅ 37 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	mangler[RadixUIAdoptionSection.jsx]	14.1 µs	14.6 µs	-3.18%

[Boshen]

Merge activity

• May 23, 6:54 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• May 23, 6:54 AM UTC: Boshen added this pull request to the Graphite merge queue.
• May 23, 7:03 AM UTC: Merged by the Graphite merge queue.