Non-null assertions fails to parse with `Not a pattern`

[mischnic]

Describe the bug

This fails to parse, but works fine with TSC: https://www.typescriptlang.org/play/?#code/NwbQhgThYJ4MIHsAONwF0CEAaABJa8yqARpmjgLw4gBQO9eUsiKIp2dD+zR6HaNIA

Input code

;[arrayCopy[currentIndex]!, arrayCopy[randomIndex]!] = [
  arrayCopy[randomIndex]!,
  arrayCopy[currentIndex]!,
]

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false
    },
    "target": "es5",
    "loose": false,
    "minify": {
      "compress": false,
      "mangle": false
    }
  },
  "module": {
    "type": "es6"
  },
  "minify": false,
  "isModule": true
}

Link to the code that reproduces this issue

https://play.swc.rs/?version=1.13.20&code=H4sIAAAAAAAAA7OOTiwqSqx0zi%2BojE6MVdRRQHCTYhVjFWwVorkUUAV1UARAmrhiuQCITKnpSAAAAA%3D%3D&config=H4sIAAAAAAAAA1WPSw7DIAwF9zkF8rrbdtE79BCIOhERP9mOVBTl7oUE0maH3xszsA5KwcwGnmotxzIkTYx0ziXhHER%2FSgKSE7IhmwRuvRWu1agd4x5tRwOiaUKpW8j3hoOLkbHjLfM22DH%2FC030iZD5ClZUh8nhVTc0Jfj4XvayfaQ%2B9tA%2F4Ad12XkxWH71TaEFh%2B0LYuVI0xQBAAA%3D

SWC Info output

No response

Expected behavior

[arrayCopy[a], arrayCopy[b]] = [
    arrayCopy[b],
    arrayCopy[a],
];

Actual behavior

fails to parse

Version

1.13.20

Additional context

No response

[kdy1]

@claude Fix LHS detection of the parser

[claude]

Claude finished @kdy1's task —— View job • claude/issue-11142-20251007-0030 • Create PR ➔

---

Fixed LHS Detection for Non-null Assertions ✅

Successfully fixed the parser's LHS detection for non-null assertions in destructuring assignments.

Completed Tasks:

• Read repository setup instructions (CLAUDE.md) - No CLAUDE.md found
• Understand the issue and reproduce the problem
• Locate the TypeScript parser code for LHS patterns
• Find where non-null assertions are handled in destructuring
• Implement the fix for LHS detection
• Test the fix with the provided example
• Run tests and linting if available
• Commit and push changes

Root Cause & Fix

Problem: TypeScript non-null assertions (!) in destructuring patterns were failing to parse with "Not a pattern" error because Expr::TsNonNull nodes weren't handled in the expression-to-pattern conversion logic.

Solution: Added handling for Expr::TsNonNull in crates/swc_ecma_lexer/src/common/parser/pat.rs at lines 345-348:

// TypeScript non-null assertion - delegate to inner expression
Expr::TsNonNull(TsNonNullExpr { expr, .. }) => {
    reparse_expr_as_pat_inner(p, pat_ty, expr)
}

This fix allows the parser to properly handle patterns like:

[arrayCopy[currentIndex]!, arrayCopy[randomIndex]!] = [
  arrayCopy[randomIndex]!,
  arrayCopy[currentIndex]!,
];

Testing Results:

• ✅ Successfully compiled parser with fix
• ✅ All 4,399 TypeScript spec tests pass
• ✅ All 51 destructuring-related tests pass
• ✅ No regressions in existing functionality
• ✅ Committed fix with test case

Commit Details:

• Branch: claude/issue-11142-20251007-0030
• Commit: e8b3caf58
• Files changed:
  • crates/swc_ecma_lexer/src/common/parser/pat.rs (fix)
  • crates/swc_ecma_parser/tests/typescript/destructuring-non-null/input.ts (test case)