Throw AbstractClassInstantiationError on abstract class instantiation.

lib/core/errors.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 Error {
   const Error();
 }
 
 class AssertionError implements Error {
 }
@@ skipping 28 matching lines @@
  */
 class IllegalArgumentException extends ArgumentError {
   const IllegalArgumentException([argument = ""]) : super(argument);
 }
 
 
 class FallThroughError implements Error {
   const FallThroughError();
 }
 
-class AbstractClassInstantiationError {
+class AbstractClassInstantiationError implements Error {
+  final String _className;
+  const AbstractClassInstantiationError(String this._className);
+  String toString() => "Cannot instantiate abstract class: '$_className'";
 }
 
 /**
  * Error thrown by the default implementation of [:noSuchMethod:] on [Object].
  */
 class NoSuchMethodError implements Error {
   final Object _receiver;
   final String _functionName;
   final List _arguments;
   final List _existingArgumentNames;
@@ skipping 59 matching lines @@
         .replaceAll('\n', '${backslash}n')
         .replaceAll('\r', '${backslash}r')
         .replaceAll('"',  '$backslash"');
       return '"$escaped"';
     }
     return _objectToString(object);
   }
 
   external static String _objectToString(Object object);
 }