Implement simple dynamic type check.

lib/compiler/implementation/typechecker.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.
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);
   String get name() => "Type checker";
 
   static final bool LOG_FAILURES = false;
 
@@ skipping 16 matching lines @@
 interface Type {
   SourceString get name();
   Element get element();
 }
 
 class TypeVariableType implements Type {
   final SourceString name;
   Element element;
   TypeVariableType(this.name, [this.element]);
 
-  toString() => name.toString();
+  toString() => name.slowToString();
 }
 
 /**
  * A statement type tracks whether a statement returns or may return.
  */
 class StatementType implements Type {
   final String stringName;
   Element get element() => null;
 
   SourceString get name() => new SourceString(stringName);
 
   const StatementType(this.stringName);
 
   static final RETURNING = const StatementType('<returning>');
   static final NOT_RETURNING = const StatementType('<not returning>');
   static final MAYBE_RETURNING = const StatementType('<maybe returning>');
 
   /** Combine the information about two control-flow edges that are joined. */
   StatementType join(StatementType other) {
     return (this === other) ? this : MAYBE_RETURNING;
   }
 
   String toString() => stringName;
 }
 
 class InterfaceType implements Type {
   final SourceString name;
-  final Element element;
+  final ClassElement element;
   final Link<Type> arguments;
 
   const InterfaceType(this.name, this.element,
                       [this.arguments = const EmptyLink<Type>()]);
 
   toString() {
     StringBuffer sb = new StringBuffer();
     sb.add(name.slowToString());
     if (!arguments.isEmpty()) {
       sb.add('<');
@@ skipping 651 matching lines @@
   }
 
   visitCatchBlock(CatchBlock node) {
     fail(node);
   }
 
   visitTypedef(Typedef node) {
     fail(node);
   }
 }