anchor.diff:      } else if (moduleId == ModuleId.corePrimitives.nested(['ToString'])) {
         return compileToString();
       } else if (moduleId == ModuleId.corePrimitives.nested(['Unit'])) {
  -      return compileUnit();
  +      return compileUnit(declarationId);
       } else if (moduleId == ModuleId.corePrimitives.nested(['Never'])) {
         return compileNever();
       } else if (moduleId == ModuleId.coreBool.nested(['Bool'])) {
  
positive.code:   List<Output> compileAny();
    List<Output> compileToString();
  
    List<Output> compileUnit();
    List<Output> compileNever();
  
    List<Output> compileBool(DeclarationId id);
  
negative.code:   }
  
    @override
    List<dart.Spec> compileUnit(DeclarationId id) {
      final mixinsAndImplementsAndMethodOverrides =
          _prepareMixinsAndImplementsAndMethodOverrides(context, id);
  
      return [
        dart.Class((b) => b
          ..annotations.add(dart.refer('sealed', packageMetaUrl))
          ..name = 'Unit'
          ..constructors.add(dart.Constructor((b) => b..constant = true))
          ..mixins.addAll(mixinsAndImplementsAndMethodOverrides.first)
          ..implements.addAll(mixinsAndImplementsAndMethodOverrides.second)
          ..methods.addAll([
            dart.Method((b) => b
              ..name = 'toString'
              ..returns = dart.refer('String', dartCoreUrl)
              ..body = dart.literalString('"unit"').code)
          ])
          ..methods.addAll(mixinsAndImplementsAndMethodOverrides.third)),
      ];
    }
  
  