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bun.sh/test/regression/issue/comma-operator-this-binding.test.ts
robobun 584946b0ce Fix comma operator optimization to preserve 'this' binding semantics (#21653)
## Summary
- Fix transpiler bug where comma expressions like `(0, obj.method)()`
were incorrectly optimized to `obj.method()`
- This preserved the `this` binding instead of stripping it as per
JavaScript semantics
- Add comprehensive regression test to prevent future issues

## Root Cause
The comma operator optimization in `src/js_parser.zig:7281` was directly
returning the right operand when the left operand had no side effects,
without checking if the expression was being used as a call target.

## Solution
- Added the same `is_call_target` check that other operators (nullish
coalescing, logical OR/AND) use
- When a comma expression is used as a call target AND the right operand
has a value for `this`, preserve the comma expression to strip the
`this` binding
- Follows existing patterns in the codebase for consistent behavior

## Test Plan
- [x] Reproduce the original bug: `(0, obj.method)()` incorrectly
preserved `this`
- [x] Verify fix: comma expressions now correctly strip `this` binding
in function calls
- [x] All existing transpiler tests continue to pass
- [x] Added regression test covering various comma expression scenarios
- [x] Tested edge cases: nested comma expressions, side effects,
different operand types

🤖 Generated with [Claude Code](https://claude.ai/code)

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Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
2025-08-09 05:11:50 -07:00

1.1 KiB