Issue 3532. Report error if one unit included twice

compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file

[Brian Wilkerson, 2012/06/12 15:34:14]

nit: copyright year

[scheglov, 2012/06/12 18:17:51]

Done.

 // 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.
 
 package com.google.dart.compiler;
 
 /**
  * Valid error codes for the errors produced by the Dart compiler.
  */
 public enum DartCompilerErrorCode implements ErrorCode {
   ENTRY_POINT_METHOD_CANNOT_HAVE_PARAMETERS(ErrorSeverity.WARNING, 
       "Main entry point method cannot have parameters"),
   ENTRY_POINT_METHOD_MAY_NOT_BE_GETTER(ErrorSeverity.WARNING,
       "Entry point \"%s\" may not be a getter"),
   ENTRY_POINT_METHOD_MAY_NOT_BE_SETTER(ErrorSeverity.WARNING,
       "Entry point \"%s\" may not be a setter"),
   ILLEGAL_DIRECTIVES_IN_SOURCED_UNIT("This source was included by %s via a "
       + "#source directive, so cannot itself contain directives"),
   IO("Input/Output error: %s"),
   MISSING_LIBRARY_DIRECTIVE("a library which is imported is missing a #library directive: %s"),
-  MISSING_SOURCE("Cannot find referenced source: %s");
+  MISSING_SOURCE("Cannot find referenced source: %s"),
+  UNIT_WAS_ALREADY_INCLUDED("Unit '%s' was already included");
   private final ErrorSeverity severity;
   private final String message;
 
   /**
    * Initialize a newly created error code to have the given message and ERROR severity.
    */
   private DartCompilerErrorCode(String message) {
     this(ErrorSeverity.ERROR, message);
   }
 
@@ skipping 18 matching lines @@
   @Override
   public SubSystem getSubSystem() {
     return SubSystem.COMPILER;
   }
 
   @Override
   public boolean needsRecompilation() {
     return true;
   }
 }