Internal libraries supported.

sdk/lib/_internal/compiler/implementation/dart2js.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 dart2js;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:uri';
 import 'dart:utf';
@@ skipping 182 matching lines @@
   if (arguments.length > 1) {
     var extra = arguments.getRange(1, arguments.length - 1);
     helpAndFail('Error: Extra arguments: ${Strings.join(extra, " ")}');
   }
 
   Map<String, SourceFile> sourceFiles = <String, SourceFile>{};
   int dartBytesRead = 0;
 
   Future<String> provider(Uri uri) {
     if (uri.scheme != 'file') {
-      throw new ArgumentError(uri);
+      throw new ArgumentError("Invalid uri '$uri'");

[ahe, 2013/01/24 10:00:57]

How about: "Unknown scheme in uri '$uri'"

[Johnni Winther, 2013/01/24 13:04:59]

Done.

     }
     String source;
     try {
       source = readAll(uriPathToNative(uri.path));
     } on FileIOException catch (ex) {
       throw 'Error: Cannot read "${relativize(cwd, uri, isWindows)}" '
             '(${ex.osError}).';
     }
     dartBytesRead += source.length;
     sourceFiles[uri.toString()] =
@@ skipping 252 matching lines @@
     } catch (ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }