refactor(parser): Avoid peek in parse_delimited_list

[leaysgur]

Out of curiosity, I've just deleted the peeking in parse_delimited_list.

Then, coverage errors show me there are only a few places missing error report for invalid trailing comma after rest element, etc.

So I added those checks manually.

In TSC, these checks seem to be done at checker, not parser. But we need this in parser for JS.

---

(Sorry, I have PASSED the test, but I am not very confident that this change is intrinsically sound.)

[graphite-app]

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #11343 will improve performances by 14.65%

_{Comparing r/delimited-list (069b843) with main (3249ab6)}

Summary

⚡ 1 improvements
✅ 37 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	mangler[cal.com.tsx]	3.5 ms	3 ms	+14.65%

[leaysgur]

At this point, there appears to be no regression in the parser benchmark.

But strangely, when I added a commit that removes the unused Lexer::lookahead related things, the regression occurs!
(Please see edit history of codespeed comment)

...🤔

[Copilot]

Pull Request Overview

Refactors parse_delimited_list to return a tuple with an optional trailing-separator span, and adds parser-level checks for invalid trailing commas in specific constructs.

• Changed all parse_delimited_list invocations to the new signature (Vec, Option<u32>)
• Added explicit error reporting for trailing commas in index signatures and parenthesized expressions
• Updated context wrappers to destructure the new tuple return

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
crates/oxc_parser/src/ts/types.rs	Switched to tuple return from parse_delimited_list and added trailing-comma error for index signatures
crates/oxc_parser/src/ts/statement.rs	Adapted enum-body parsing to the new parse_delimited_list signature
crates/oxc_parser/src/js/object.rs	Updated object-expression parsing to destructure the new return
crates/oxc_parser/src/js/module.rs	Simplified import/export specifier parsing with the new signature
crates/oxc_parser/src/js/expression.rs	Hooked into trailing-comma span for parentheses, arrays, and calls
crates/oxc_parser/src/cursor.rs	Changed parse_delimited_list to return trailing-separator info and marked unused peek_at

Comments suppressed due to low confidence (2)

crates/oxc_parser/src/ts/types.rs:1233

• There should be a unit test covering the new trailing-comma error path in index signatures to ensure this diagnostic fires when a comma precedes ].

if let Some(comma_span) = comma_span {

crates/oxc_parser/src/js/expression.rs:212

• Add tests to validate that a trailing comma inside parentheses triggers the fatal_error path and correctly reports the unexpected comma.

if let Some(comma_span) = comma_span {

[Boshen]

Merge activity

• May 28, 8:30 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 28, 8:30 AM UTC: Boshen added this pull request to the Graphite merge queue.
• May 28, 8:37 AM UTC: Merged by the Graphite merge queue.