Heads-up: UB due to misuse of mem::uninitialized will soon lead to panic

[RalfJung]

Here, this crate causes UB by "Producing an invalid value". Concretely, it creates an arbitrary T with mem::uninitialized(). In the near future the call to mem::uninitialized() will panic to avoid UB, and our crater run determined that this crate will be affected. (Specifically, the test suite of this crate creates an unitialized String, which is invalid.)

mem::uninitialized() is deprecated since Rust 1.39. The intended replacement is MaybeUninit, which tracks the possibility of uninitialized values at the type level to make sure the compiler does not make any false assumptions.