Use Object as supertype in face of invalid supertypes.

sdk/lib/_internal/compiler/implementation/resolution/members.dart

Index: sdk/lib/_internal/compiler/implementation/resolution/members.dart
diff --git a/sdk/lib/_internal/compiler/implementation/resolution/members.dart b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
index 3f03c4edecebf9a8694f1008537b8fb896b078fd..cadfcc34f1f7d30f3af4f1d9d59d30957753aa9e 100644
--- a/sdk/lib/_internal/compiler/implementation/resolution/members.dart
+++ b/sdk/lib/_internal/compiler/implementation/resolution/members.dart
@@ -4111,15 +4111,15 @@ class ClassResolverVisitor extends TypeDefinitionVisitor {
     if (supertype != null) {
       if (identical(supertype.kind, TypeKind.MALFORMED_TYPE)) {
         compiler.reportError(superclass, MessageKind.CANNOT_EXTEND_MALFORMED);
-        return null;
+        return compiler.objectClass.computeType(compiler);

[karlklose, 2014/01/28 13:30:03]

Extract a getter for this type. Also it should be objectClass.rawType.

[Johnni Winther, 2014/01/29 10:26:09]

Done.

       } else if (!identical(supertype.kind, TypeKind.INTERFACE)) {
         compiler.reportError(superclass.typeName,
             MessageKind.CLASS_NAME_EXPECTED);
-        return null;
+        return compiler.objectClass.computeType(compiler);
       } else if (isBlackListed(supertype)) {
         compiler.reportError(superclass, MessageKind.CANNOT_EXTEND,
             {'type': supertype});
-        return null;
+        return compiler.objectClass.computeType(compiler);
       }
     }
     return supertype;