Implement DotShorthandConstructorInvocationImpl support for argument list context.

Bug: https://github.com/dart-lang/sdk/issues/61843
Change-Id: I54118ea6599c30e36918dd3255f6c79b2f02280e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/457801
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer_plugin/lib/src/utilities/completion/optype.dart

@@ -1837,6 +1837,8 @@ class _OpTypeAstVisitor extends GeneralizingAstVisitor<void> {
       var parent = node.parent;
       if (parent is Annotation) {
         return 'annotation';
+      } else if (parent is DotShorthandConstructorInvocation) {
+        return 'constructor';
       } else if (parent is EnumConstantArguments) {
         return 'enumConstantArguments';
       } else if (parent is ExtensionOverride) {

pkg/analyzer_plugin/test/src/utilities/completion/optype_test.dart

@@ -1131,6 +1131,21 @@ void f() {
     );
   }
 
+  Future<void> test_dotShorthandConstructorInvocation_arguments() async {
+    addTestSource('''
+class C {
+  C({int? i});
+}
+void f() {
+  C _ = .new(^);
+},
+''');
+    await assertOpType(
+      completionLocation: 'ArgumentList_constructor_named',
+      namedArgs: true,
+    );
+  }
+
   Future<void> test_dotShorthandConstructorInvocation_noTarget() async {
     addTestSource('''
 class C {