anchor.diff:  
         for (ClassMember classMember
             in toSet(declaredMember.classBuilder, overriddenMembers)) {
  -        assert(useConsolidated || !classMember.hasDeclarations);
           Member overriddenMember = classMember.getMember(hierarchy);
           Substitution classSubstitution;
           if (classBuilder.cls != overriddenMember.enclosingClass) {
  
positive.code: void _toSet(ClassBuilder classBuilder, Iterable<ClassMember> members,
      Set<ClassMember> result) {
    for (ClassMember member in members) {
      if (member.hasDeclarations &&
          (!useConsolidated || classBuilder == member.classBuilder)) {
        _toSet(classBuilder, member.declarations, result);
      } else {
        result.add(member);
  
negative.code: 
    void recordAbstractMember(ClassMember member) {
      abstractMembers ??= <ClassMember>[];
      if (member.hasDeclarations && classBuilder == member.classBuilder) {
        abstractMembers.addAll(member.declarations);
      } else {
        abstractMembers.add(member);
  