Find diagnostic locations for use in new compiler API.

dart/frog/leg/frog_leg.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.
 
 #library('frog_leg');
 
 #import('../../lib/uri/uri.dart');
 #import('../lang.dart', prefix: 'frog');
 #import('api.dart', prefix: 'api');
 #import('io/io.dart', prefix: 'io');
@@ skipping 17 matching lines @@
     Completer<String> completer = new Completer<String>();
     completer.complete(source);
     return completer.future;
   }
 
   void handler(Uri uri, int begin, int end, String message, bool fatal) {
     if (uri === null && !fatal) {
       world.info('[leg] $message');
       return;
     }
-    print(message);
-    if (fatal && throwOnError) new AbortLeg(message);
+    print('$uri:$begin:$end: $message');
+    if (fatal && throwOnError) throw new AbortLeg(message);
   }
 
   // TODO(ahe): We expect the future to be complete and call value
   // directly. In effect, we don't support truly asynchronous API.
   String code = api.compile(uri, libraryRoot, provider, handler).value;
   if (code === null) return false;
   world.legCode = code;
   world.jsBytesWritten = code.length;
   return true;
 }
 
 class AbortLeg {
   final message;
   AbortLeg(this.message);
   toString() => 'Aborted due to --throw-on-error: $message';
 }