anchor.diff:      var fullPath = p.join(packageDir, relativePath);
       var lib = _getLibraryElement(fullPath);
       if (lib == null) return [];
  -    Set<String> refs = new SplayTreeSet();
  +    var refs = new SplayTreeSet<String>();
       lib.importedLibraries.forEach((le) {
         refs.add(_normalizeLibRef(le.librarySource.uri, package, packageDir));
       });
  
positive.code:   final String _packagePath;
    final UriResolver _packageResolver;
    final AnalysisContext _context;
    final _cachedLibs = <String, List<String>>{};
  
    LibraryScanner._(this.packageName, this._packagePath, this._packageResolver,
        this._context);
  
negative.code:       refs.add(_normalizeLibRef(le.librarySource.uri, package, packageDir));
      });
      refs.remove('dart:core');
      return new List<String>.unmodifiable(refs);
    }
  
    LibraryElement _getLibraryElement(String path) {
  