Don't use ClassElementImpl for now in override checking.

TBR

I'd like to land this for now, but I probably will reintroduce it a
bit later. The problem is that this again the same problem with
handles, and I don't want to make it into internal build as is.

R=brianwilkerson@google.com

Change-Id: I98c37b2c5dadf2d5450a536471fc002fc5b247d2
Reviewed-on: https://dart-review.googlesource.com/76221
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
diff --git a/pkg/analyzer/lib/src/error/inheritance_override.dart b/pkg/analyzer/lib/src/error/inheritance_override.dart
index fbbb768..1d48cf7 100644
--- a/pkg/analyzer/lib/src/error/inheritance_override.dart
+++ b/pkg/analyzer/lib/src/error/inheritance_override.dart
@@ -251,7 +251,7 @@
 
   void _verifyClass(SimpleIdentifier classNameNode,
       {List<ClassMember> members: const [], WithClause withClause}) {
-    ClassElementImpl element = classNameNode.staticElement;
+    ClassElement element = classNameNode.staticElement;
     LibraryElement library = element.library;
     InterfaceTypeImpl type = element.type;