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#![allow(incomplete_features)]
#![feature(const_generics, const_evaluatable_checked)]
/// Like `MaybeUninit<[u8; N]>`, but always considered uninitialized.
///
/// You might want this if you want to surround fields with padding,
/// without impacting the alignment of the struct containing the
/// field (the way that use of an `#[repr(align(N))]` would).
#[repr(transparent)]
#[derive(Clone, Copy)]
pub struct AlwaysUninit<const N: usize>(
    core::mem::MaybeUninit<[OveralignedU8; (N + 7) / 8]>
) where [(); (N + 7) / 8]: Sized;

// an alignment of 8 is small enough as to not generally
// matter much in practice
#[repr(C, align(8))]
#[derive(Clone, Copy)]
struct OveralignedU8(u8);

const _: [(); 1] = [(); (
    core::mem::size_of::<AlwaysUninit<64>>() >= 64
) as usize];

#[repr(C)]
#[derive(Clone)]
pub struct Example {
    _pad0: AlwaysUninit<64>,
    v0: core::cell::Cell<usize>,
    _pad1: AlwaysUninit<64>,
    v1: usize,
    _pad2: AlwaysUninit<64>,
}

pub fn can_we_copy_efficiently(c: &Example) -> Example {
    c.clone()
}