anchor.diff:    /// Packages are sorted so that inner packages are before outer.
     final List<_Package> _packages = [];
   
  -  /// The list of paths of all files inside the context.
  -  final List<String> _contextPathList = [];
  +  /// The set of paths of all files inside the context.
  +  final Set<String> _contextPathSet = {};
   
     /// The list of paths of all SDK libraries.
     final List<String> _sdkLibraryPathList = [];
  
positive.code:         }
        } else {
          // Not in a package, include all libraries of the context.
          contextPathList = _contextPathList;
        }
      } else {
        // In Blaze workspaces, consider declarations from the entire context
        contextPathList = _contextPathList;
      }
  
      var contextLibraries = <Library>[];
      _addLibrariesWithPaths(
        contextLibraries,
        contextPathList,
        excludingLibraryOfPath: path,
      );
  
  
negative.code:       }
  
        if (package != null) {
          List<String> contextPathList = contextPaths = [];
          var containingFolder = package.folderInRootContaining(path);
          if (containingFolder != null) {
            for (var contextPath in _contextPathSet) {
              // `lib/` can see only libraries in `lib/`.
              // `test/` can see libraries in `lib/` and in `test/`.
              if (package.containsInLib(contextPath) ||
  