test(parser): combine test cases for let as identifier

[overlookmotel]

Follow-on after #16840 and #16857. We had a few test cases relating to the same thing, and one of them called the undescriptive oxc.js. Combine them, and rename the test case files with a more accurate name.

[overlookmotel]

• test(parser): combine test cases for let as identifier #16861 👈 (View in Graphite)
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[overlookmotel]

Merge activity

• Dec 14, 9:23 PM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Dec 14, 9:27 PM UTC: overlookmotel added this pull request to the Graphite merge queue.
• Dec 14, 9:36 PM UTC: Merged by the Graphite merge queue.

[charliecreates]

The consolidation looks correct and the snapshot updates are consistent with the file moves, but the new fixture names/comments are now slightly misleading because they bundle optional chaining cases under “member expression”. Consider renaming or splitting to keep fixtures narrowly scoped and easier to maintain/search.

Additional notes (3)

• Maintainability | tasks/coverage/misc/fail/let-member-expression.js:1-12
  The file comment says it tests member/call expressions, but it also includes several optional chaining cases. That’s fine functionally, but it makes the fixture name/comment slightly misleading and harder to grep later when someone is looking specifically for optional chaining behavior.

Consider either splitting optional chaining back out or renaming/commenting the fixture to reflect both concerns (e.g., member/call and optional chaining) so future changes don’t accidentally drop coverage.

• Maintainability | tasks/coverage/misc/fail/let-member-expression.js:1-3
'use strict'; is redundant in a file that is explicitly described as a module fixture, since ES modules are always strict mode. If the harness treats .js in misc/fail as a module via sourceType: "module", this line is noise and can slightly obscure what is being tested (reserved-word parsing vs. strictness). If, however, the harness relies on 'use strict' to force strictness for .js inputs, the comment should say that explicitly to avoid future confusion.

• Maintainability | tasks/coverage/misc/pass/let-member-expression.cjs:1-10
  In the passing .cjs fixture, the comment says “in script”, but the file also contains optional chaining. Depending on what this coverage suite is intended to assert, optional chaining may require a minimum language version/feature flag in some parsers.

If the test runner’s configuration ever varies (e.g., running with older ECMAScript targets), this fixture could become an accidental coupling between “script vs module let identifier rules” and “optional chaining enabled”.

Summary of changes

What changed

This PR consolidates and renames parser coverage fixtures around using the reserved keyword let as an identifier in member/call expressions.

• New negative fixture: tasks/coverage/misc/fail/let-member-expression.js
  • Combines prior failing cases from let-optional-chaining.js and oxc.js into one module/strict-mode fixture.
• New positive fixture: tasks/coverage/misc/pass/let-member-expression.cjs
  • Consolidates prior passing optional chaining script fixture into a single .cjs script fixture.
• Removed redundant/unclear fixtures:
  • Deleted tasks/coverage/misc/fail/let-optional-chaining.js
  • Deleted tasks/coverage/misc/fail/oxc.js (previously non-descriptive)
  • Deleted tasks/coverage/misc/pass/let-optional-chaining.cjs
• Snapshot update: tasks/coverage/snapshots/parser_misc.snap
  • Updates counts (Negative Passed: 122/122 → 121/121) and rewires expected error locations to the new consolidated file/line numbers.