anchor.diff:    /// [_disambiguateMember], [_disambiguateInternalMember],
     /// [_disambiguateOperator], and [reservePublicMemberName].
     final NamingScope instanceScope = NamingScope();
  -  final Map<String, jsAst.Name> userInstanceMembers = HashMap();
  -  final Map<String, String> userInstanceMembersOriginalName = HashMap();
  -  final Map<MemberEntity, jsAst.Name> internalInstanceMembers = HashMap();
  -  final Map<String, jsAst.Name> userInstanceOperators = HashMap();
  -  final Map<jsAst.Name, jsAst.Name> userGetters = HashMap();
  -  final Map<jsAst.Name, jsAst.Name> userSetters = HashMap();
  +  final Map<String, jsAst.Name> userInstanceMembers = {};
  +  final Map<String, String> userInstanceMembersOriginalName = {};
  +  final Map<MemberEntity, jsAst.Name> internalInstanceMembers = {};
  +  final Map<String, jsAst.Name> userInstanceOperators = {};
  +  final Map<jsAst.Name, jsAst.Name> userGetters = {};
  +  final Map<jsAst.Name, jsAst.Name> userSetters = {};
     final Map<TypeVariableEntity, jsAst.Name> _typeVariableNames = {};
   
     Map<String, String> createMinifiedInstanceNameMap() {
  
positive.code: // BSD-style license that can be found in the LICENSE file.
  
  library js_backend.namer;
  
  import 'dart:collection' show HashMap;
  
  import 'package:front_end/src/api_unstable/dart2js.dart'
      show $0, $9, $A, $Z, $_, $a, $g, $s, $z;
  
negative.code:   // parts with the fast-startup emitter.
    String get typesOffsetName => r'typesOffset';
  
    Map<FunctionType, jsAst.Name> functionTypeNameMap = {};
  
    FunctionTypeNamer _functionTypeNamer;
  
  