Allow creation of public symbols using MirrorSystem.getSymbol when passing a null library.

runtime/lib/mirrors_patch.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.
 
-import "dart:nativewrappers";

[rmacnak, 2013/11/20 00:27:46]

We haven't needed this since the introduction of MirrorReference...

 // TODO(ahe): Move _symbol_dev.Symbol to its own "private" library?
 import "dart:_collection-dev" as _symbol_dev;
 
 /**
  * Returns a [MirrorSystem] for the current isolate.
  */
 patch MirrorSystem currentMirrorSystem() {
   return _Mirrors.currentMirrorSystem();
 }
 
@@ skipping 55 matching lines @@
         result.write(char);
       }
     }
     if (add_setter_suffix) {
       result.write('=');
     }
     return result.toString();
   }
 
   /* patch */ static Symbol getSymbol(String name, [LibraryMirror library]) {
-    if (library is! LibraryMirror ||
+    if ((library != null && library is! _LocalLibraryMirror) ||

[ahe, 2013/11/21 09:07:02]

Why are you checking for is! _LocalLibraryMirror?

My understanding is that it is too protect _mangleName from being called with
anything that isn't a _MirrorReference.

Using reflection, I can instantiate _LocalLibraryMirror and ensure it has a
bogus value for the field _reflectee. I believe I can provoke a crash that way
if Mirrors_mangleName makes too many assumptions. I'd argue that you should
remove the type test here and replace line 84 with:

if (library != null) {
  name = _mangleName(name, library._reflectee as _MirrorReference);
}

However, if _mangleName is so brittle, then you probably also need to write:

if (library != null) {
  name = _mangleName(name as String, library._reflectee as _MirrorReference);
}

If _mangleName is an instance method on _MirrorReference, you can reduce this
to:

if (library != null) {
  name = library._reflectee._mangleName(name as String);
}

Regardless, _mangleName can be invoked reflectively, so it should probably be
checking for String in C++, so really the first lines of this method should just
be:

if (library != null) {
  name = library._reflectee._mangleName(name);
} else if (name.startsWith('_')) {
  throw new ArgumentError("'$name' is private so this method needs a library");
}

         ((name.length > 0) && (name[0] == '_') && (library == null))) {
       throw new ArgumentError(library);
     }
     if (library != null) name = _mangleName(name, library._reflectee);
     return new _symbol_dev.Symbol.unvalidated(name);
   }
 
   static _mangleName(String name, _MirrorReference lib)
       native "Mirrors_mangleName";
 }
 
 // TODO(rmacnak): Eliminate this class.
 class MirroredCompilationError {
   final String message;
 
   MirroredCompilationError(this.message);
 
   String toString() {
     return "Compile-time error during mirrored execution: <$message>";
   }
 }