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 produces a value of type geometry::ray::ShearingTransformCache with mem::uninitialized(), which contains a Permulation, which is an enum and thus must always contain a valid enum variant. 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.

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.