MalformedType used for all invalid type annotations.

sdk/lib/_internal/compiler/implementation/universe/universe.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library universe;
 
 import '../closure.dart';
 import '../elements/elements.dart';
 import '../dart2jslib.dart';
 import '../tree/tree.dart';
@@ skipping 364 matching lines @@
    * The type of the receiver. Any subtype of that type can be the
    * target of the invocation.
    */
   final DartType receiverType;
 
   TypedSelector(DartType this.receiverType, Selector selector)
     : super(selector.kind,
             selector.name,
             selector.library,
             selector.argumentCount,
-            selector.namedArguments);
+            selector.namedArguments) {
+    // Invariant: Typed selector can not be based on a malformed type.
+    assert(!identical(receiverType.kind, TypeKind.MALFORMED_TYPE));
+  }
 
   /**
    * Check if [element] will be the one used at runtime when being
    * invoked on an instance of [cls].
    */
   bool hasElementIn(ClassElement cls, Element element) {
     Element resolved = cls.lookupMember(element.name);
     if (identical(resolved, element)) return true;
     if (resolved == null) return false;
     if (identical(resolved.kind, ElementKind.ABSTRACT_FIELD)) {
@@ skipping 43 matching lines @@
     ClassElement cls = self;
     if (cls.isSubclassOf(other)) {
       // Resolve an invocation of [element.name] on [self]. If it
       // is found, this selector is a candidate.
       return hasElementIn(self, element) && appliesUntyped(element, compiler);
     }
 
     return false;
   }
 }