[trinovantes]

By deep immutability, I meant Foo{Bar*} where Bar has further nested structs. It's tedious to have to manually mark every field in the tree as const to achieve deep immutability, which can easily be stripped off with a cast.

What if some of those structs are from libraries and I can't mark their inner fields as const? Yes, most libraries I've used are well tested so I don't need to worry about them modifying my fields but there's no guarantee that I won't.

> I'd also add even if you thought you could enforce this at runtime

I'm well aware this is a hard problem. It was something I frequently discussed with my lab mate who wrote his thesis on this exact topic. I'm simply saying it would be a nice-to-have construct like assertions.