Bug I not trying creator a MonoBehaviour using the 'new' keyword, but editor console warning

warning info : You are trying to create a MonoBehaviour using the 'new' keyword. This is not allowed. MonoBehaviours can only be added using AddComponent(). Alternatively, your script can inherit from ScriptableObject or no base class at all

code:

Code (CSharp):

1. protected List<List<LayoutInfo>> layoutList { get; } = new List<List<LayoutInfo>>();

LayoutInfo code:

Code (CSharp):

1. protected struct LayoutInfo
2.         {
3.             public RectTransform rectTransform;
4.  
5.             public Vector2 min;
6.             public Vector2 preferred;
7.             public Vector2 flexible;
8.         }

 

Putting that code in an empty scene doesn't trigger the warning for me, so the warning is probably coming from somewhere else.