fix(minifier): preserve return value of @__PURE__ IIFE in return statements

[camc314]

Closes #18028

[camc314]

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This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
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• fix(mangler): reserve names from eval-containing scopes #18037
• fix(minifier): preserve return value of @__PURE__ IIFE in return statements #18036 👈 (View in Graphite)
• fix(minifier): skip inlining constant in scopes with eval #17926
• main

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[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing c/01-15-fix_minifier_preserve_return_value_of___pure___iife_in_return_statements (17630cd) with c/01-12-fix_minifier_skip_inlining_constant_in_scopes_with_eval (5b501b9)}

Summary

✅ 38 untouched benchmarks
⏩ 7 skipped benchmarks¹

Footnotes

1. 7 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 a bug where @__PURE__ annotated IIFE return values were incorrectly being removed in return statement contexts. The fix renames and reimplements the helper function to more accurately detect when an expression's result is truly unused.

Changes:

• Renamed is_descendant_of_block to is_expression_result_unused with corrected logic that checks if the immediate parent is an expression statement
• Updated all call sites to use the renamed function
• Added comprehensive test cases verifying the fix handles return statements correctly

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
crates/oxc_minifier/src/peephole/substitute_alternate_syntax.rs	Renamed and reimplemented helper function to correctly identify unused expression results, fixing incorrect behavior in return statement contexts
crates/oxc_minifier/src/peephole/remove_unused_expression.rs	Added test cases verifying the fix preserves IIFE return values in return statements while still removing them in expression statement contexts

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[graphite-app]

Merge activity

• Jan 16, 5:20 AM UTC: Boshen added this pull request to the Graphite merge queue.