anchor.diff:    }
   
     bool _dagCheck(DartType type) {
  -    int /*?*/ ref = _backrefs[type];
  +    int? ref = _backrefs[type];
       if (ref != null) {
         _add('\$$ref');
         return true;
  
positive.code:     return true;
    }
  
    void _visit(DartType type, DartType parent) {
      type.accept(this, parent);
    }
  
  
negative.code:     js.Expression helperAccess =
          _emitter.staticFunctionAccess(_commonElements.findType);
  
      js.Expression loadTypeCall(TypeRecipe recipe, String? helperLocal) {
        js.Expression recipeExpression =
            _recipeEncoder.encodeGroundRecipe(_emitter, recipe);
        return js.js(r'#(#)', [helperLocal ?? helperAccess, recipeExpression]);
  