[element model] migrate type_constraint_gatherer_test

Change-Id: I01708c6e7e8b2e87b9f906ed13b6e94ba6511d62
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/405603
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

pkg/analyzer/test/generated/elements_types_mixin.dart

@@ -120,7 +120,6 @@ mixin ElementsTypesMixin {
   TypeImpl get unknownInferredType => UnknownInferredType.instance;
 
   VoidTypeImpl get voidNone => VoidTypeImpl.instance;
-
   ClassElementImpl class_({
     required String name,
     bool isAbstract = false,
@@ -151,6 +150,31 @@ mixin ElementsTypesMixin {
     return fragment;
   }
 
+  ClassElementImpl class_2({
+    required String name,
+    bool isAbstract = false,
+    bool isAugmentation = false,
+    bool isSealed = false,
+    InterfaceType? superType,
+    List<TypeParameterElement2> typeParameters = const [],
+    List<InterfaceType> interfaces = const [],
+    List<InterfaceType> mixins = const [],
+    List<MethodElementImpl> methods = const [],
+  }) {
+    return class_(
+        name: name,
+        isAbstract: isAbstract,
+        isAugmentation: isAugmentation,
+        isSealed: isSealed,
+        superType: superType,
+        typeParameters: typeParameters
+            .map((e) => e.asElement as TypeParameterElementImpl)
+            .toList(),
+        interfaces: interfaces,
+        mixins: mixins,
+        methods: methods);
+  }
+
   InterfaceTypeImpl comparableNone(DartType type) {
     var coreLibrary = typeProvider.intElement.library;
     var element = coreLibrary.getClass('Comparable')!;