Fixed a nil pointer dereference crash that occurred when requesting signature help on parenthesized call expressions with specific trigger parameters.

Problem

The language server would crash with a nil pointer dereference when:

1. A user had a call expression likesomeCall()
2. They wrapped it in parentheses:(someCall())
3. Signature help was triggered at specific positions withtriggerCharacter: "(" andtriggerKind: 2

The crash occurred inGetSignatureHelpItems at line 103 when trying to accesscandidateInfo.candidateInfo without first checking ifcandidateInfo was nil.

Root Cause

ThegetCandidateOrTypeInfo function can returnnil when it doesn't match any of the three invocation types (callInvocation, typeArgsInvocation, contextualInvocation). However, the calling code assumedcandidateInfo would never be nil and attempted to access its fields directly, causing a panic.

Solution

Added a simple nil check forcandidateInfo before accessing its fields:

ifcandidateInfo==nil {// We didn't have any sig help items produced by the TS compiler.returnnil}

This defensive programming approach prevents the crash while maintaining existing behavior for valid cases. WhencandidateInfo is nil, the function now returns nil (no signature help) instead of crashing.

Testing

• Added a test casesignatureHelpParenthesizedCall that reproduces the crash scenario
• Verified the test fails with a panic before the fix and passes after
• Confirmed all existing signature help tests continue to pass
• Build and formatting checks pass

Fixes#1415.

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn moreCopilot coding agent tips in the docs.