Refactor resolution code in the vm to properly handle ambiguity errors.

runtime/vm/exceptions.cc

 // 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.
 
 #include "vm/exceptions.h"
 
 #include "vm/dart_api_impl.h"
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
 #include "vm/flags.h"
@@ skipping 376 matching lines @@
   return caller.script();
 }
 
 
 // Allocate a new instance of the given class name.
 // TODO(hausner): Rename this NewCoreInstance to call out the fact that
 // the class name is resolved in the core library implicitly?
 RawInstance* Exceptions::NewInstance(const char* class_name) {
   const String& cls_name = String::Handle(Symbols::New(class_name));
   const Library& core_lib = Library::Handle(Library::CoreLibrary());
-  Class& cls = Class::Handle(core_lib.LookupClass(cls_name));
+  // No ambiguity error expected: passing NULL.
+  Class& cls = Class::Handle(core_lib.LookupClass(cls_name, NULL));
   ASSERT(!cls.IsNull());
   // There are no parameterized error types, so no need to set type arguments.
   return Instance::New(cls);
 }
 
 
 // Assign the value to the field given by its name in the given instance.
 void Exceptions::SetField(const Instance& instance,
                           const Class& cls,
                           const char* field_name,
@@ skipping 220 matching lines @@
       break;
   }
 
   return DartLibraryCalls::InstanceCreate(library,
                                           *class_name,
                                           *constructor_name,
                                           arguments);
 }
 
 }  // namespace dart