Make test of malformed types a dynamic type error.

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 576 matching lines @@
         return graph.addConstantBool(false, compiler);
       }
     }
     return node;
   }
 
   HInstruction visitTypeConversion(HTypeConversion node) {
     HInstruction value = node.inputs[0];
     DartType type = node.typeExpression;
     if (type != null) {
+      if (type.kind == TypeKind.MALFORMED_TYPE) {
+        // Malformed types are treated as dynamic statically, but should
+        // throw a type error at runtime.
+        return node;
+      }
       if (!type.treatAsRaw || type.kind == TypeKind.TYPE_VARIABLE) {
         return node;
       }
       if (type.kind == TypeKind.FUNCTION) {
         // TODO(johnniwinther): Optimize function type conversions.
         return node;
       }
     }
     return removeIfCheckAlwaysSucceeds(node, node.checkedType);
   }
@@ skipping 905 matching lines @@
       // that knows it is not of a specific Type.
     }
 
     for (HIf ifUser in notIfUsers) {
       changeUsesDominatedBy(ifUser.elseBlock, input, convertedType);
       // TODO(ngeoffray): Also change uses for the then block on a HType
       // that knows it is not of a specific Type.
     }
   }
 }