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//@ check-pass
#![feature(coerce_unsized)]
// Ensure that unsizing structs that contain ZSTs at non-zero offsets don't ICE
use std::ops::CoerceUnsized;
#[repr(C)]
pub struct BoxWithZstTail<T: ?Sized>(Box<T>, ());
impl<S: ?Sized, T: ?Sized> CoerceUnsized<BoxWithZstTail<T>> for BoxWithZstTail<S> where
Box<S>: CoerceUnsized<Box<T>>
{
}
pub fn noop_dyn_upcast_with_zst_tail(
b: BoxWithZstTail<dyn ToString + Send>,
) -> BoxWithZstTail<dyn ToString> {
b
}
fn main() {
let original = "foo";
let boxed = BoxWithZstTail(Box::new(original) as Box<dyn ToString + Send>, ());
let noop_upcasted = noop_dyn_upcast_with_zst_tail(boxed);
assert_eq!(original, noop_upcasted.0.to_string());
}
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