ICE: rustc crashed on const generics

[qwerty19106]

Test code:

#![feature(const_generics)]

use std::mem::MaybeUninit;

#[repr(transparent)]
pub struct OsThreadStack<const N: usize>(MaybeUninit<[u64; N]>);

fn main() {

}

It produced error:

error: internal compiler error: src/librustc/ty/sty.rs:2311: expected constant usize, got Const {
    ty: usize,
    val: Param(
        N/#0,
    ),
}

Playground version: rustc 1.37.0-nightly (2019-05-29 37d001e)

playground

[varkor]

This may be the same as #61337. Both should be added as regression tests when this is fixed.

[qwerty19106]

Also this code give other error:

#![feature(const_generics)]

use core::mem::MaybeUninit;

#[repr(C)]
pub struct OsThreadStack<const N: usize> {
    stack: MaybeUninit<[u64; N / 8]>
}

fn main() {
}

error: internal compiler error: constant in type had an ignored error
 --> src/main.rs:7:5
  |
7 |     stack: MaybeUninit<[u64; N / 8]>
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[varkor]

@qwerty19106: thanks, I've opened that as a new issue (as it has a different error message): #61368.

[varkor]

Note that this only occurs when #[repr(transparent)] is present.

[varkor]

I have a fix for this (separate from the one for #61337).