Use identical() instead of == for elements in RuntimeTypeEqualityVisitor.

See dart-lang/mockito#658 (comment)

Change-Id: I5b9e4b1d82ec935bcd2097ec76cf5a8e28c5e29e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/312205
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>

Author: scheglov

pkg/analyzer/lib/src/dart/element/runtime_type_equality.dart

@@ -88,7 +88,7 @@ class RuntimeTypeEqualityVisitor
   @override
   bool visitInterfaceType(InterfaceType T1, DartType T2) {
     if (T2 is InterfaceType &&
-        T1.element == T2.element &&
+        identical(T1.element, T2.element) &&
         _compatibleNullability(T1, T2)) {
       var T1_typeArguments = T1.typeArguments;
       var T2_typeArguments = T2.typeArguments;
@@ -167,7 +167,7 @@ class RuntimeTypeEqualityVisitor
   bool visitTypeParameterType(TypeParameterType T1, DartType T2) {
     return T2 is TypeParameterType &&
         _compatibleNullability(T1, T2) &&
-        T1.element == T2.element;
+        identical(T1.element, T2.element);
   }
 
   @override