gotools/gopls/internal/golang/signature_help.go

// SignatureHelp returns information about the signature of the innermost
// function call enclosing the position, or nil if there is none.
// On success it also returns the parameter index of the position.
func SignatureHelp(ctx context.Context, snapshot *cache.Snapshot, fh file.Handle, position protocol.Position) (*protocol.SignatureInformation, int, error) { … }

// Note: callExpr may be nil when signatureHelp is invoked outside the call
// argument list (golang/go#69552).
func builtinSignature(ctx context.Context, snapshot *cache.Snapshot, callExpr *ast.CallExpr, name string, pos token.Pos) (*protocol.SignatureInformation, int, error) { … }

func activeParameter(callExpr *ast.CallExpr, numParams int, variadic bool, pos token.Pos) (activeParam int) { … }

func stringToSigInfoDocumentation(s string, options *settings.Options) *protocol.Or_SignatureInformation_documentation { … }