rust/src/test/ui/impl-trait/region-escape-via-bound-contravariant.rs
2019-05-12 18:46:43 +01:00

24 lines
524 B
Rust

// In contrast to `region-escape-via-bound-invariant`, in this case we
// *can* return a value of type `&'x u32`, even though `'x` does not
// appear in the bounds. This is because `&` is contravariant, and so
// we are *actually* returning a `&'y u32`.
//
// See https://github.com/rust-lang/rust/issues/46541 for more details.
// run-pass
#![allow(dead_code)]
#![feature(in_band_lifetimes)]
trait Trait<'a> { }
impl Trait<'b> for &'a u32 { }
fn foo(x: &'x u32) -> impl Trait<'y>
where 'x: 'y
{
x
}
fn main() { }