MalformedType used for all invalid type annotations.

sdk/lib/_internal/compiler/implementation/ssa/optimize.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.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 553 matching lines @@
         return graph.addConstantBool(true, constantSystem);
       } else {
         return graph.addConstantBool(false, constantSystem);
       }
     // TODO(karlklose): remove the hasTypeArguments check.
     } else if (expressionType.isUseful()
                && !expressionType.canBeNull()
                && !RuntimeTypeInformation.hasTypeArguments(type)) {
       DartType receiverType = expressionType.computeType(compiler);
       if (receiverType != null) {
-        if (compiler.types.isSubtype(receiverType, type)) {
+        if (!receiverType.isMalformed &&
+            !type.isMalformed &&
+            compiler.types.isSubtype(receiverType, type)) {
           return graph.addConstantBool(true, constantSystem);
         } else if (expressionType.isExact()) {
           return graph.addConstantBool(false, constantSystem);
         }
       }
     }
     return node;
   }
 
   HInstruction visitTypeConversion(HTypeConversion node) {
@@ skipping 890 matching lines @@
     HInstruction receiver = interceptor.receiver;
     for (var user in receiver.usedBy) {
       if (user is HInterceptor && interceptor.dominates(user)) {
         user.interceptedClasses = interceptor.interceptedClasses;
       }
     }
   }
 
   // TODO(ngeoffray): Also implement it for non-intercepted calls.
 }