anchor.diff:    Future<void> _addProposal_flutterSwapWithParent() async {
       var child = flutter.identifyNewExpression(node);
       if (!flutter.isWidgetCreation(child)) {
  -      _coverageMarker();
         return;
       }
   
       // NamedExpression (child:), ArgumentList, InstanceCreationExpression
       var expr = child.parent?.parent?.parent;
       if (expr is! InstanceCreationExpression) {
  -      _coverageMarker();
         return;
       }
       InstanceCreationExpression parent = expr;
  
positive.code:       var iterableType = iterable.staticType;
        if (iterableType is! InterfaceType ||
            iterableType.element != typeProvider.listElement) {
          _coverageMarker();
          return;
        }
      }
      // body should be Block
      if (forEachStatement.body is! Block) {
        _coverageMarker();
        return;
      }
      Block body = forEachStatement.body;
  
negative.code:     // prepare expression type
      var type = expression.staticType;
      if (type.isVoid) {
        return;
      }
      // prepare excluded names
  