anchor.diff:    js_ast.Expression visitSetLiteral(SetLiteral node) {
       // TODO(markzipan): remove const check when we use front-end const eval
       if (!node.isConst) {
  -      var setType = visitInterfaceType(InterfaceType(
  -          _linkedHashSetClass, Nullability.legacy, [node.typeArgument]));
  +      var setType = _emitInterfaceType(
  +          InterfaceType(
  +              _linkedHashSetClass, Nullability.legacy, [node.typeArgument]),
  +          emitNullability: false);
         if (node.expressions.isEmpty) {
           return js.call('#.new()', [setType]);
         }
  
positive.code:     if (itemType == const DynamicType()) return list;
  
      // Call `new JSArray<E>.of(list)`
      var arrayType =
          InterfaceType(_jsArrayClass, Nullability.legacy, [itemType]);
      return js.call('#.of(#)', [_emitType(arrayType), list]);
    }
  
    js_ast.Expression _emitConstList(
  
negative.code:       //   the nullability is meaningless (ie. class A extends B) where B is the
        //   InterfaceType.
        // * The InterfaceType is the Null type.
        // * Non-null constructor calls.
        return typeRep;
      }
  
  