Make signature help arg index handling more like Strada (microsoft#1586)

Author: jakebailey

internal/fourslash/tests/signatureHelpCrash_test.go

@@ -0,0 +1,32 @@
+package fourslash_test
+
+import (
+	"testing"
+
+	"github.com/microsoft/typescript-go/internal/fourslash"
+	. "github.com/microsoft/typescript-go/internal/fourslash/tests/util"
+	"github.com/microsoft/typescript-go/internal/lsp/lsproto"
+	"github.com/microsoft/typescript-go/internal/testutil"
+)
+
+func TestSignatureHelpTokenCrash2(t *testing.T) {
+	t.Parallel()
+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+	const content = `
+function foo<T, U>(x: string, y: T, z: U) {
+
+}
+
+foo<number,number>/*1*/("hello", 123,456)
+`
+	f := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	f.VerifySignatureHelp(t, &fourslash.SignatureHelpCase{
+		MarkerInput: "1",
+		Expected:    nil,
+		Context: &lsproto.SignatureHelpContext{
+			IsRetrigger:      false,
+			TriggerCharacter: PtrTo("("),
+			TriggerKind:      lsproto.SignatureHelpTriggerKindTriggerCharacter,
+		},
+	})
+}

internal/ls/completions.go

@@ -4692,12 +4692,12 @@ type argumentInfoForCompletions struct {
 
 func getArgumentInfoForCompletions(node *ast.Node, position int, file *ast.SourceFile, typeChecker *checker.Checker) *argumentInfoForCompletions {
 	info := getImmediatelyContainingArgumentInfo(node, position, file, typeChecker)
-	if info == nil || info.isTypeParameterList || info.invocation.callInvocation == nil || info.argumentIndex == nil {
+	if info == nil || info.isTypeParameterList || info.invocation.callInvocation == nil {
 		return nil
 	}
 	return &argumentInfoForCompletions{
 		invocation:    info.invocation.callInvocation.node,
-		argumentIndex: *info.argumentIndex,
+		argumentIndex: info.argumentIndex,
 		argumentCount: info.argumentCount,
 	}
 }