Stop building blind: report errors with factories and parametrized types.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 1469)
+++ runtime/vm/parser.cc	(working copy)
@@ -6394,10 +6394,9 @@
   if (!type_arguments.IsNull() &&
       (type_arguments.Length() !=
           Class::Handle(constructor.owner()).NumTypeArguments())) {
-    // TODO(regis): report proper error once we can.
-    // ErrorMsg(pos, "Incorrect number of type arguments, expected %d got %d",
-    //     Class::Handle(constructor.owner()).NumTypeArguments(),
-    //     type_arguments.Length());
+    ErrorMsg(pos, "Incorrect number of type arguments, expected %d got %d",
+        Class::Handle(constructor.owner()).NumTypeArguments(),
+        type_arguments.Length());
   }
 }