[boost] [any] [basic_any] This seems like a little pearl in Boost 1.77, but it's a bit underdocumented?

I just discovered basic_any which is a very nice addition for me. However it's a bit under-documented for the moment. For example: - I assume it's stack-allocated, does it allocate on the heap if assigned an object larger than the stack (like small_vector) or is this not allowed (like static_vector)? - An idea would also be to add a flag which breaks compilation if an object larger than the OptimizeForSize argument is assigned? - (For detail) If allocated on the stack, are the first bytes of the basic_any the same as the contained object? /Viktor