Issue 3532. Report error if one unit included twice

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

Index: compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java
diff --git a/compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java b/compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java
index 4797109173e276b6391e4fd8065403862bbbd620..054fcdd563bdbccf09c41932ff0d465926ec3bd9 100644
--- a/compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java
+++ b/compiler/java/com/google/dart/compiler/DartCompilerErrorCode.java
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -18,7 +18,8 @@ public enum DartCompilerErrorCode implements ErrorCode {
       + "#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");

[Brian Wilkerson, 2012/06/12 18:26:29]

nit: perhaps instead of "included" we should say "sourced"?

[scheglov, 2012/06/12 18:38:20]

"sourced" sounds as slang for me.
I've used to it however.

Spec says in "12.3 Includes":
An include directive speci
es a URI where a Dart compilation unit that should
be incorporated into the current library may be found.

So, it looks for me that best word from from spec would be "incorporated" :-)
Or "included" by the name (but not keyword) or directive.
Well, this is mess...

   private final ErrorSeverity severity;
   private final String message;