perf(ecma_parser): start oxc-style token payload rewrite

[kdy1]

Description:

This starts the long-lived swc_ecma_parser performance rewrite with a parser-facing token payload refactor that follows the oxc-style plan without changing the public parser API.

What changed:

• Buffer now owns separate current/lookahead token payload slots instead of saving and restoring lexer token_value during generic peek().
• TypeScript parser checkpoints now persist the current payload slot directly, so backtracking restores parser state without re-shuffling lexer payload state.
• Flow/TypeScript contextual-word checks that only need equality now use borrowed string comparisons instead of materializing or cloning Atoms on hot paths.

Why this helps:

• It removes the generic Buffer::peek() payload swap from the main parser hot path.
• It keeps lookahead payloads in parser-owned slots, which is closer to the target architecture for the ongoing lexer/parser rewrite.
• It reduces unnecessary Atom work in TS/Flow ambiguity checks.

Local benchmark spot checks on April 20, 2026:

• es/parser/colors: from roughly 4.16–4.59 µs to 3.05–3.07 µs
• es/lexer/colors: from roughly 1.15–1.19 µs to 0.90–0.93 µs
• es/parser/typescript: measured at roughly 51.3–52.5 ms after the change

Validation used:

• git submodule update --init --recursive
• cargo fmt --all
• cargo test -p swc_ecma_parser
• cargo bench -p swc_ecma_parser --bench parser -- --warm-up-time 0.01 --measurement-time 0.01 'es/parser/colors'
• cargo bench -p swc_ecma_parser --bench lexer -- --warm-up-time 0.01 --measurement-time 0.01 'es/lexer/colors'
• cargo bench -p swc_ecma_parser --bench parser -- --warm-up-time 0.01 --measurement-time 0.01 'es/parser/typescript'

This is phase 1 of the rewrite PR. After the Benchmark workflow finishes, I plan to use the CodSpeed report to choose the next optimization step.

BREAKING CHANGE:

None.

Related issue (if exists):

N/A

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Latest commit: 5439aaf

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[codspeed-hq]

Merging this PR will not alter performance

✅ 219 untouched benchmarks
⏩ 31 skipped benchmarks¹

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_{Comparing kdy1/oxc-parser-rewrite (5439aaf) with main (fe38342)}

Footnotes

1. 31 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. ↩

[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	27M (27766728 bytes)

Commit: 634d294