ices/69296.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#69296

unsafe fn f<T: ?Sized>(ptr: *mut T, new: *mut u8) -> *mut T {
    use std::mem;

    let mut parts: [*mut u8; mem::size_of::<*mut T>() / mem::size_of::<*mut u8>()] =
        mem::transmute(ptr);
    parts[0] = new;
    mem::transmute(parts)
}

fn main() {}

=== stdout ===
=== stderr ===
error: generic parameters may not be used in const operations
 --> /home/runner/work/glacier/glacier/ices/69296.rs:4:50
  |
4 |     let mut parts: [*mut u8; mem::size_of::<*mut T>() / mem::size_of::<*mut u8>()] =
  |                                                  ^ cannot perform const operation using `T`
  |
  = note: type parameters may not be used in const expressions
  = help: use `#![feature(const_generics)]` and `#![feature(const_evaluatable_checked)]` to allow generic const expressions

error: aborting due to previous error

==============

[JohnTitor]

(It's duplicate)