LSP: Jump to the function name

[shinichy]

Improved the "Go to Definition" command to jump to the function name instead of the beginning of the function keyword.

Example:

function foo() {
   ...
}

foo(); // "Go to Definition" jumps to `foo` instead of `function`.

[shinichy]

I tried to port the logic from src/services/goToDefinition.ts in the TypeScript repository.

[Copilot]

Pull Request Overview

This PR improves the “Go to Definition” command so that it now jumps directly to a function’s name instead of its leading keyword. Key changes include:

• Updating the definition lookup in internal/ls/definition.go to focus on the function name.
• Renaming several helper functions to exported versions (e.g., GetResolvedSignature, IsCallLikeExpression) for consistency.
• Adding new utility functions in internal/ast/utilities.go to support the enhanced navigation.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/ls/definition.go	Refactored definition location logic and added helper functions.
internal/checker/utilities.go	Renamed and added exported helper functions for signature checks.
internal/checker/jsx.go	Updated signature resolution to use exported helper functions.
internal/checker/flow.go	Updated calls to use the exported GetResolvedSignature function.
internal/checker/checker.go	Replaced internal function calls with their exported counterparts.
internal/ast/utilities.go	Added a utility to determine property access context.

Comments suppressed due to low confidence (4)

internal/ls/definition.go:19

• [nitpick] Consider renaming 'tryGetSignatureDeclaration' to better convey its intent (e.g., 'getSignatureDeclaration') if it always returns a declaration or nil.

calledDeclaration := tryGetSignatureDeclaration(checker, node)

internal/checker/utilities.go:1297

• Ensure that the change to an exported function name is accompanied by updated documentation comments to clarify its usage.

func IsCallLikeExpression(node *ast.Node) bool {

internal/checker/checker.go:7904

• [nitpick] Verify that all calls to the renamed 'GetResolvedSignature' are updated consistently and that its behavior is properly documented.

func (c *Checker) GetResolvedSignature(node *ast.Node, candidatesOutArray *[]*Signature, checkMode CheckMode) *Signature {

internal/ast/utilities.go:2654

• [nitpick] Add a documentation comment for 'IsRightSideOfPropertyAccess' to clearly describe its purpose and usage in the codebase.

func IsRightSideOfPropertyAccess(node *Node) bool {