anchor.diff:  class _MemberTable {
     final _ClassTable parent;
     final Class class_; // Null for top-level.
  -  final Map<String, Member> members = <String, Member>{};
  +  Map<String, Member> _members;
   
     Library get library => parent.library;
   
  -  _MemberTable(this.parent, this.class_) {
  -    class_.procedures.forEach(addMember);
  -    class_.fields.forEach(addMember);
  -    class_.constructors.forEach(addMember);
  -  }
  -
  -  _MemberTable.topLevel(this.parent) : class_ = null {
  -    library.procedures.forEach(addMember);
  -    library.fields.forEach(addMember);
  +  _MemberTable(this.parent, this.class_);
  +
  +  _MemberTable.topLevel(this.parent) : class_ = null;
  +
  +  Map<String, Member> get members {
  +    if (_members == null) {
  +      _members = <String, Member>{};
  +      if (class_ != null) {
  +        class_.procedures.forEach(addMember);
  +        class_.fields.forEach(addMember);
  +        class_.constructors.forEach(addMember);
  +      } else {
  +        library.procedures.forEach(addMember);
  +        library.fields.forEach(addMember);
  +      }
  +    }
  +    return _members;
     }
   
     String getDisambiguatedName(Member member) {
  
positive.code: }
  
  class _ClassTable {
    Library library;
    final Map<String, _MemberTable> classes = <String, _MemberTable>{};
  
    void build(Library library) {
      this.library = library;
      classes[LibraryIndex.topLevel] = new _MemberTable.topLevel(this);
      for (var class_ in library.classes) {
        classes[class_.name] = new _MemberTable(this, class_);
      }
    }
  
    String get containerName {
  
negative.code: 
    /// Indexes the libraries with the URIs given in [libraryUris].
    LibraryIndex(Program program, Iterable<String> libraryUris) {
      var libraryUriSet = libraryUris.toSet();
      for (var library in program.libraries) {
        var uri = '${library.importUri}';
        if (libraryUriSet.contains(uri)) {
          _libraries[uri] = new _ClassTable(library);
        }
      }
    }
  