alt Hacker NewsCreator of Ante here. It's just a term I made up for mutation which does not change the "shape" of data in a way that can invalidate any of that data. Mutating a struct or tuple field, even if nested, is stable for example, but mutating an optional string to None is not because you may be dropping a string which there may be a reference to somewhere.
I see, so would it would only be relevant to unions, or would adding a new node to a linked list or pushing another element in a dynamic array or setting a pointer to null also count?