fix(formatter): remove unnecessary parentheses for single-member union types

[Dunqing]

Single-member union/intersection types (e.g., (| number)[]) were getting unnecessary parentheses, outputting (number)[] instead of number[].

In Prettier's Babel AST, single-member unions don't exist (they're unwrapped by the parser), so parenthesization never triggers. In oxc, the parser creates these nodes, so the fix:

1. Makes single-member unions/intersections return false from needs_parentheses
2. Adds effective_parent helper that looks through single-member unions/intersections so inner types correctly check against the grandparent context (e.g., keyof T inside a single-member union inside TSArrayType correctly sees TSArrayType as its parent)

Closes #18941

[Dunqing]

• fix(formatter): preserve comment between callee and optional chaining operator #19020
• fix(formatter): remove unnecessary parentheses for single-member union types #19018 👈 (View in Graphite)
• refactor(formatter): handle TSParenthesizedType with unreachable statement #19017
• fix(formatter): preserve parentheses around await with private field access #19014
• fix(formatter): preserve parentheses around nested sequence expressions #19013
• fix(formatter): add space before type annotation with leading comment #19012
• fix(formatter): keep spread with callback on same line #18999
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing 02-06-fix_formatter_remove_unnecessary_parentheses_for_single-member_union_types (259996f) with 02-06-refactor_formatter_handle_tsparenthesizedtype_with_unreachable_statement (6d53fc1)}

Summary

✅ 46 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. ↩

[Copilot]

Pull request overview

This PR fixes unnecessary parentheses being added to single-member union and intersection types in the formatter, aligning oxc's output with Prettier's behavior.

Changes:

• Added effective_parent helper function that looks through single-member unions/intersections to find the true parent context
• Modified single-member union/intersection types to return false from needs_parentheses
• Updated all type parenthesization checks to use effective_parent when determining parent context

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/oxc_formatter/src/parentheses/ts_type.rs	Core implementation: added effective_parent helper and updated all needs_parentheses implementations for TypeScript types to use it
crates/oxc_formatter/tests/fixtures/ts/union-type/single-member.ts	Test input covering single-member unions/intersections in arrays and standalone
crates/oxc_formatter/tests/fixtures/ts/union-type/single-member.ts.snap	Expected output showing correct formatting without unnecessary parentheses

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[graphite-app]

Merge activity

• Feb 6, 1:05 PM UTC: Dunqing added this pull request to the Graphite merge queue.
• Feb 6, 1:35 PM UTC: Merged by the Graphite merge queue.