Fix nil pointer dereference in completion at property start after JSDoc

[Copilot]

Requesting completions at the beginning of a property name preceded by JSDoc caused a nil pointer panic when accessing contextToken.Kind.

Root Cause

Variable shadowing in getRelevantTokens: Used := instead of =, creating a local variable that shadowed the return parameter, causing contextToken to return nil.

// Before: shadows the return parameter
contextToken := astnav.FindPrecedingToken(file, previousToken.Pos())

// After: assigns to return parameter
contextToken = astnav.FindPrecedingToken(file, previousToken.Pos())

Missing nil guards in tryGetClassLikeCompletionSymbols: tryGetObjectTypeDeclarationCompletionContainer can return a non-nil declaration when contextToken is nil (e.g., when location is an identifier in a class body).

Changes

• Fixed variable shadowing in getRelevantTokens (line 2753)
• Added nil checks before accessing contextToken.Kind and contextToken.Parent in tryGetClassLikeCompletionSymbols (lines 1447, 1461, 1464, 1471)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Crash completing beginning of property name when preceded by JSDoc</issue_title>
<issue_description>```ts
export class SomeInterface {
/** ruh-roh! /
/$1*/property: string;
}

export class SomeClass {
/** ruh-roh! /
/$2*/property = "value";
}

Request completions at the beginning of either property (markers `/*$1*/` and `/*$2*/`).

error] panic handling requesttextDocument/completionruntime error: invalid memory address or nil pointer dereferencegoroutine 23769 [running]:
runtime/debug.Stack()
runtime/debug/stack.go:26 +0x5e
github.com/microsoft/typescript-go/internal/lsp.(*Server).recover(0xc0001e4008, 0xc026483a10)
github.com/microsoft/typescript-go/internal/lsp/server.go:872 +0x58
panic({0xbddea0?, 0x16c8b70?})
runtime/panic.go:783 +0x132
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getCompletionData.func15()
github.com/microsoft/typescript-go/internal/ls/completions.go:1447 +0xba
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getCompletionData.func18(...)
github.com/microsoft/typescript-go/internal/ls/completions.go:1689
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getCompletionData(0xc029141380, {0x107d088, 0xc029141320}, 0xc036d90008, 0xc005362f08, 0x85, 0xc0097e1e00)
github.com/microsoft/typescript-go/internal/ls/completions.go:1717 +0x1edf
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getCompletionsAtPosition(0xc029141380, {0x107d088, 0xc029141320}, 0xc005362f08, 0x85, 0x0)
github.com/microsoft/typescript-go/internal/ls/completions.go:383 +0x2cf
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).ProvideCompletion(0xc029141380, {0x107d088, 0xc029141320}, {0xc0035e8690?, 0xc029141320?}, {0x35e8690?, 0xc0?}, 0xc02b74b0f0)
github.com/microsoft/typescript-go/internal/ls/completions.go:44 +0xc8
github.com/microsoft/typescript-go/internal/lsp.(*Server).handleCompletion(0xc00140c008?, {0x107d088?, 0xc029141320?}, 0xc0035e8690?, 0x40b92c?)
github.com/microsoft/typescript-go/internal/lsp/server.go:1208 +0x39
github.com/microsoft/typescript-go/internal/lsp.init.func1.registerLanguageServiceDocumentRequestHandler[...].16({0x107d088, 0xc029141320}, 0xc026483a10)
github.com/microsoft/typescript-go/internal/lsp/server.go:621 +0x130
github.com/microsoft/typescript-go/internal/lsp.(*Server).handleRequestOrNotification(0xc0001e4008, {0x107d0c0?, 0xc01d1484b0?}, 0xc026483a10)
github.com/microsoft/typescript-go/internal/lsp/server.go:502 +0x14b
github.com/microsoft/typescript-go/internal/lsp.(*Server).dispatchLoop.func1()
github.com/microsoft/typescript-go/internal/lsp/server.go:405 +0x3a
created by github.com/microsoft/typescript-go/internal/lsp.(*Server).dispatchLoop in goroutine 10
github.com/microsoft/typescript-go/internal/lsp/server.go:425 +0x9ad

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Crash completing beginning of property name when preceded by JSDoc #2253

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