IMO there should be attributes for declaring allocators. Or builtin functions that have the effect of marking their callers with such attributes (e.g., an `__a

IMO there should be attributes for declaring allocators. Or builtin functions that have the effect of marking their callers with such attributes (e.g., an `__allocated()` function to say a pointer is indeed now to be considered a pointer to a new storage allocation, with a given size and optional type, and a `__freed()` function to say that a pointer is indeed now to be considered a dangling pointer to a deallocated object.