Fix for using enums as InterfaceType(s) when resynthesize from Kernel.

pkg/analyzer/lib/src/kernel/resynthesize.dart

Index: pkg/analyzer/lib/src/kernel/resynthesize.dart
diff --git a/pkg/analyzer/lib/src/kernel/resynthesize.dart b/pkg/analyzer/lib/src/kernel/resynthesize.dart
index 0931edff0db979af808457f9e5b5aa9d26bb53e7..d3c23f7e9c5b4f8cbccdcf94d746c04de16760d3 100644
--- a/pkg/analyzer/lib/src/kernel/resynthesize.dart
+++ b/pkg/analyzer/lib/src/kernel/resynthesize.dart
@@ -745,10 +745,26 @@ class _KernelUnitResynthesizerContextImpl
   @override
   InterfaceType getInterfaceType(
       ElementImpl context, kernel.Supertype kernelType) {
+    if (kernelType.classNode.isEnum) {
+      return null;

[Brian Wilkerson, 2017/08/31 19:54:15]

Does this mean that we won't be able to resynthesize enum classes? If so, is
this a temporary situation? 

[scheglov, 2017/08/31 19:55:23]

We can resynthesize enums.
We just should not allow to say that "class C extends MyEnum {}".
This is a compilation error, and we consider this as "class C extends Object
{}".

+    }
     return _getInterfaceType(
         context, kernelType.className.canonicalName, kernelType.typeArguments);
   }
 
+  @override
+  List<InterfaceType> getInterfaceTypes(
+      ElementImpl context, List<kernel.Supertype> types) {
+    var interfaceTypes = <InterfaceType>[];
+    for (kernel.Supertype kernelType in types) {
+      InterfaceType interfaceType = getInterfaceType(context, kernelType);
+      if (interfaceType != null) {
+        interfaceTypes.add(interfaceType);
+      }
+    }
+    return interfaceTypes;
+  }
+
   @override
   ConstructorElementImpl getRedirectedConstructor(
       kernel.Constructor kernelConstructor, kernel.Procedure kernelFactory) {