ices/62222.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#62222

#![feature(const_generics)]

use std::mem::MaybeUninit;

#[repr(transparent)]
pub struct Vector<T, const N: usize>([T; N]);

impl<T, const N: usize> Vector<T, {N}> {
    pub fn x(self) -> T {
        let mut head = MaybeUninit::<T>::uninit();
        let mut tail = MaybeUninit::<[T; N - 1]>::uninit();
        let mut from = MaybeUninit::new(self);
        let tailp: *mut T = unsafe { mem::transmute(&mut tail) };
        let fromp: *mut MaybeUninit<T> = unsafe { mem::transmute(&mut from) };
        unsafe {
            head.as_mut_ptr().write(
                fromp
                    .replace(MaybeUninit::uninit())
                    .assume_init()
            );
        }
        for i in 1..N {
            unsafe {
                tailp.add(i - 1).write(
                    fromp
                        .add(i)
                        .replace(MaybeUninit::uninit())
                        .assume_init()
                );
            }
        }
        unsafe { tail.assume_init(); } // Drop the tail
        unsafe { head.assume_init() }
    }
}

fn main() {}

=== stdout ===
=== stderr ===
error[E0433]: failed to resolve: use of undeclared type or module `mem`
  --> /home/runner/work/glacier/glacier/ices/62222.rs:13:38
   |
13 |         let tailp: *mut T = unsafe { mem::transmute(&mut tail) };
   |                                      ^^^ use of undeclared type or module `mem`

error[E0433]: failed to resolve: use of undeclared type or module `mem`
  --> /home/runner/work/glacier/glacier/ices/62222.rs:14:51
   |
14 |         let fromp: *mut MaybeUninit<T> = unsafe { mem::transmute(&mut from) };
   |                                                   ^^^ use of undeclared type or module `mem`

warning: the feature `const_generics` is incomplete and may cause the compiler to crash
 --> /home/runner/work/glacier/glacier/ices/62222.rs:1:12
  |
1 | #![feature(const_generics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0433`.
==============

[Alexendoo]

This one is not actually fixed, I'll update it later today (and on the issue thread) to reflect that

I just merged a few that are definitely fixed but I want to double check all these const_generic ones that just came through. I believe some of them are still ICEs but just need updating slightly