fix(es/minifier): Handle unused parameters with default values

[kdy1]

When a function parameter has a default value and is not used, the minifier can now optimize it away. Previously, Pat::Assign patterns were not being handled due to a TODO comment.

Fixes #9610

Generated with Claude Code

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[kdy1]

@claude I think PR requires lots of test cases verifying various input and interactions with other rules. Fix it

[claude]

Claude finished @kdy1's task —— View job

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Added Comprehensive Test Cases for Unused Parameters with Default Values

• Read the current implementation to understand the changes
• Read existing test cases to understand test patterns
• Identify test scenarios for comprehensive coverage
• Create test fixtures for various scenarios:
  • 9610-keep-fargs - Test interaction with keep_fargs: true
  • 9610-side-effects - Default values with side effects
  • 9610-arrow-functions - Arrow functions with default params
  • 9610-methods - Object and class methods
  • 9610-destructuring - Destructuring patterns with defaults
  • 9610-nested-defaults - Nested default patterns
  • 9610-mixed-params - Mixed used/unused parameters
• Run tests to generate output files
• Verify fixture tests pass (8/8 passed)
• Run execution tests (2116 passed, 1 ignored)
• Format code
• Commit and push changes

Test Cases Added

Test	Description	Verifies
9610-keep-fargs	keep_fargs: true preserves unused defaults	Option interaction
9610-side-effects	Defaults with getSideEffect() and new Date() preserved	Side effect handling
9610-arrow-functions	Arrow functions with unused defaults	Different function types
9610-methods	Object/class methods with unused defaults	Method handling
9610-destructuring	Object/array destructuring with defaults	Destructuring patterns
9610-nested-defaults	Nested destructuring with defaults	Complex patterns
9610-mixed-params	Mixed used/unused params with defaults	Edge cases

All tests pass: 8 fixture tests + 2116 execution tests.
• claude/issue-9610-20260123-0241

[github-actions]

Binary Sizes

File	Size
swc.linux-x64-gnu.node	28M (28665032 bytes)

Commit: a578dde

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing claude/issue-9610-20260123-0241 (04b8c9c) with main (81daaaa)}

Summary

✅ 184 untouched benchmarks
⏩ 1 skipped benchmark¹

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩