Removed IllegalAccessException and UnsupportedOperationException.

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();
 }
 
+/**
+ * Error thrown by the runtime system when an assert statement fails.
+ */
 class AssertionError implements Error {
 }
 
+/**
+ * Error thrown by the runtime system when a type assertion fails.
+ */
 class TypeError implements AssertionError {
 }
 
+/**
+ * Error thrown by the runtime system when a cast operation fails.
+ */
 class CastError implements Error {
 }
 
 /**
  * Error thrown when a function is passed an unacceptable argument.
- */class ArgumentError implements Error {
+ */
+ class ArgumentError implements Error {
   final message;
 
   /** The [message] describes the erroneous argument. */
   const ArgumentError([this.message = ""]);
 
   String toString() {
     if (message != null) {
       return "Illegal argument(s): $message";
     }
     return "Illegal argument(s)";
@@ skipping 99 matching lines @@
         .replaceAll('"',  '$backslash"');
       return '"$escaped"';
     }
     return _objectToString(object);
   }
 
   external static String _objectToString(Object object);
 }
 
 
+/**
+ * The operation was not allowed by the object.
+ *
+ * This [Error] is thrown when a class cannot implement
+ * one of the methods in its signature.
+ */
+class UnsupportedError implements Error {
+  final String message;
+  UnsupportedError(this.message);
+  String toString() => message;
+}
+
+/**
+ * The operation was not allowed by the current state of the object.
+ *
+ * This is a generic error used for a variety of different erroneous
+ * actions. The message should be descriptive.
+ */
+class StateError implements Error {
+  final String message;
+  StateError(this.message);
+  String toString() => message;
+}
+
+
 class OutOfMemoryError implements Error {
   const OutOfMemoryError();
   String toString() => "Out of Memory";
 }
 
 class StackOverflowError implements Error {
   const StackOverflowError();
   String toString() => "Stack Overflow";
 }