Implement simple dynamic type check.

lib/compiler/implementation/ssa/optimize.dart

 // Copyright (c) 2011, 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.
 
 interface OptimizationPhase {
   String get name();
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 440 matching lines @@
 
   HInstruction visitTypeGuard(HTypeGuard node) {
     HInstruction value = node.guarded;
     // If the union of the types is still the guarded type than the incoming
     // type was a subtype of the guarded type, and no check is required.
     HType combinedType = value.propagatedType.union(node.guardedType);
     return (combinedType == value.propagatedType) ? value : node;
   }
 
   HInstruction visitIs(HIs node) {
-    Type type = node.typeName;
+    Type type = node.typeExpression;
     Element element = type.element;
     if (element.kind === ElementKind.TYPE_VARIABLE) {
       compiler.unimplemented("visitIs for type variables");
     }
 
     HType expressionType = node.expression.propagatedType;
     if (element === compiler.objectClass
         || element === compiler.dynamicClass) {
       return graph.addConstantBool(true);
     } else if (expressionType.isInteger()) {
@@ skipping 503 matching lines @@
         }
       }
       if (!canBeMoved) continue;
 
       // This is safe because we are running after GVN.
       // TODO(ngeoffray): ensure GVN has been run.
       set_.add(current);
     }
   }
 }