Fix panic in inlay hints for tuple types

[Copilot]

Fixes #2039

Fix crash in VSCode: Unhandled case in Node.ElementList: KindTupleType

Summary

Fixed a crash that occurred when using TypeScript inlay hints with tuple types. The crash happened when the language server tried to display type information for parameters with tuple types like [string][].

Plan

• Understand the issue: ElementList() method doesn't handle KindTupleType
• Add KindTupleType case to ElementList() method in internal/ast/ast.go
• Create a fourslash test to reproduce the issue
• Run the test to verify it fails before the fix (confirmed with baseline creation)
• Apply the fix
• Verify the test passes after the fix
• Run linters and existing tests to ensure no regressions
• Run codeql checker for security validation
• Address PR feedback: Move test from gen to tests directory

Changes Made

1. Fixed ElementList() in internal/ast/ast.go: Added handling for KindTupleType by returning the Elements field from TupleTypeNode
2. Added test TestInlayHintsTupleTypeCrash: Reproduces the original issue with tuple types in inlay hints (now in internal/fourslash/tests/)
3. Generated baseline files: Showing the fix works correctly and displays type hints for tuple types

Testing & Validation

✅ Test passes in new location
✅ All existing tests pass
✅ Linting passes - 0 issues
✅ Formatting check passes
✅ CodeQL security check - no issues found

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Crash in VSCode: Unhandled case in Node.ElementList: KindTupleType</issue_title>
<issue_description>## Stack trace

[Error - 7:18:48 PM] Request textDocument/inlayHint failed.
  Message: InternalError: panic handling request textDocument/inlayHint: Unhandled case in Node.ElementList: KindTupleType
  Code: -32603 
panic handling request textDocument/inlayHint Unhandled case in Node.ElementList: KindTupleType goroutine 278400 [running]:
runtime/debug.Stack()
	runtime/debug/stack.go:26 +0x64
github.com/microsoft/typescript-go/internal/lsp.(*Server).recover(0x14000000f00, 0x140f4912d20)
	github.com/microsoft/typescript-go/internal/lsp/server.go:571 +0x44
panic({0x10528cb00?, 0x1407513e710?})
	runtime/panic.go:783 +0x120
github.com/microsoft/typescript-go/internal/ast.(*Node).ElementList(0x0?)
	github.com/microsoft/typescript-go/internal/ast/ast.go:1073 +0xf8
github.com/microsoft/typescript-go/internal/ast.(*Node).Elements(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:1077
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).getInlayHintLabelParts.func1(0x14046d7a040)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:524 +0x4524
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).getInlayHintLabelParts(0x14003c489e8?, 0x1408f0b0380?)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:745 +0x90
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).typeToInlayHintParts(0x140bfb36000, 0x104fdd56c?)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:313 +0x50
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).getParameterDeclarationTypeHints(0x140bfb36000, 0x1052ffba0?)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:304 +0x84
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).addParameterTypeHint(0x140bfb36000, 0x14089784f50, 0x1408ea4b260)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:280 +0x50
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).visitFunctionLikeForParameterType(0x140bfb36000, 0x140bf3e41e0)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:266 +0xd8
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).visit(0x140bfb36000, 0x140bf3e41e0)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:94 +0x2e8
github.com/microsoft/typescript-go/internal/ast.visitNodes(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:28
github.com/microsoft/typescript-go/internal/ast.visitNodeList(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:37
github.com/microsoft/typescript-go/internal/ast.(*CallExpression).ForEachChild(0x140bd532c60, 0x1407513e500)
	github.com/microsoft/typescript-go/internal/ast/ast.go:6849 +0x114
github.com/microsoft/typescript-go/internal/ast.(*Node).ForEachChild(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:242
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).visit(0x140bfb36000, 0x140bd532c60)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:101 +0x390
github.com/microsoft/typescript-go/internal/ast.visit(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:21
github.com/microsoft/typescript-go/internal/ast.(*ExpressionStatement).ForEachChild(0x14000091808?, 0x1407513e4e0?)
	github.com/microsoft/typescript-go/internal/ast/ast.go:3637 +0x34
github.com/microsoft/typescript-go/internal/ast.(*Node).ForEachChild(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:242
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).visit(0x140bfb36000, 0x14181e50d80)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:101 +0x390
github.com/microsoft/typescript-go/internal/ast.visitNodes(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:28
github.com/microsoft/typescript-go/internal/ast.visitNodeList(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:37
github.com/microsoft/typescript-go/internal/ast.(*Block).ForEachChild(0x14089784ee0?, 0x1407513e4e0)
	github.com/microsoft/typescript-go/internal/ast/ast.go:3681 +0x74
github.com/microsoft/typescript-go/internal/ast.(*Node).ForEachChild(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:242
github.com/microsoft/typescript-go/internal/ls.(*inlayHintState).visit(0x140bfb36000, 0x14172841e60)
	github.com/microsoft/typescript-go/internal/ls/inlay_hints.go:101 +0x390
github.com/microsoft/typescript-go/internal/ast.visit(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:21
github.com/microsoft/typescript-go/internal/ast.(*FunctionDeclaration).ForEachChild(0x141af1eda20, 0x1407513e4a0)
	github.com/microsoft/typescript-go/internal/ast/ast.go:4106 +0x1a0
github.com/microsoft/typescript-go/internal/ast.(*Node).ForEachChild(...)
	github.com/microsoft/typescript-go/internal/ast/ast.go:242
github.com/microsoft/typescript-go/internal/ls.(*inlayHint...

</details>

- Fixes microsoft/typescript-go#2039

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[jakebailey]

#2052 fixed this bug, so now this PR only contains the test which I'd like to still have.