rust/tests/ui/issues/issue-41936-variance-coerce-unsized-cycle.rs

// check-pass
#![allow(dead_code)]
// Regression test for #41936. The coerce-unsized trait check in
// coherence was using subtyping, which triggered variance
// computation, which failed because it required type info for fields
// that had not (yet) been computed.

#![feature(unsize)]
#![feature(coerce_unsized)]

use std::{marker,ops};

// Change the array to a non-array, and error disappears
// Adding a new field to the end keeps the error
struct LogDataBuf([u8;8]);

struct Aref<T: ?Sized>
{
    // Inner structure triggers the error, removing the inner removes the message.
    ptr: Box<ArefInner<T>>,
}
impl<T: ?Sized + marker::Unsize<U>, U: ?Sized> ops::CoerceUnsized<Aref<U>> for Aref<T> {}

struct ArefInner<T: ?Sized>
{
    // Even with this field commented out, the error is raised.
    data: T,
}

fn main(){}