Address the remaining review comments on http://chromiumcodereview.appspot.com/9431029.

lib/compiler/implementation/typechecker.dart

Index: lib/compiler/implementation/typechecker.dart
diff --git a/lib/compiler/implementation/typechecker.dart b/lib/compiler/implementation/typechecker.dart
index c44326180dce5407de98ff00452b1a6f585a8dad..13478662c4f1c03d429f063ae4cb98d9c399bdcb 100644
--- a/lib/compiler/implementation/typechecker.dart
+++ b/lib/compiler/implementation/typechecker.dart
@@ -61,19 +61,20 @@ class StatementType implements Type {
 }
 
 class InterfaceType implements Type {
-  final SourceString name;
   final Element element;
   final Link<Type> arguments;
 
-  const InterfaceType(this.name, this.element,
+  const InterfaceType(name, this.element,
                       [this.arguments = const EmptyLink<Type>()]);
 
+  SourceString get name() => element.name;
+
   toString() {
     StringBuffer sb = new StringBuffer();
     sb.add(name.slowToString());
     if (!arguments.isEmpty()) {
       sb.add('<');
-      arguments.printOn(sb);
+      arguments.printOn(sb, ', ');
       sb.add('>');
     }
     return sb.toString();