anchor.diff:  /// root path.
   /// Entire other packages are allowed inside a package's root.
   class TrielikePackageTree implements PackageTree {
  -  final Map<String, _TrielikePackageTreeHelper> _map = {};
  +  final Map<String, _PackageTrieNode> _map = {};
   
     /// A list of all packages.
     final List<SimplePackage> _packages = [];
  
positive.code: 
    @override
    SimplePackage? packageOf(Uri file) {
      var currentMapHelper = _map[file.scheme];
      if (currentMapHelper == null) return null;
      var path = file.toString();
      var potential = <SimplePackage>[];
      if (_isMatch(path, currentMapHelper, potential)) {
        return currentMapHelper.package;
      }
      var segments = file.pathSegments;
  
      for (var i = 0; i < segments.length - 1; i++) {
        var segment = segments[i];
        currentMapHelper = currentMapHelper!.map[segment];
        if (currentMapHelper == null) break;
        if (_isMatch(path, currentMapHelper, potential)) {
          return currentMapHelper.package;
        }
      }
      if (potential.isEmpty) return null;
  
negative.code:     }
    }
  
    bool _checkConflict(_PackageTrieNode currentTrieNode,
        SimplePackage newPackage, void Function(Object error) onError) {
      if (currentTrieNode.package != null) {
        var existingPackage = currentTrieNode.package!;
        // Trying to add package that is inside the existing package.
        // 1) If it's an exact match it's not allowed (i.e. the roots can't be
        //    the same).
  