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#![feature(const_mut_refs)]
#![feature(inline_const_pat)]
use std::marker::PhantomData;
#[derive(PartialEq, Eq)]
pub struct InvariantRef<'a, T: ?Sized>(&'a T, PhantomData<&'a mut &'a T>);
#[derive(PartialEq, Eq)]
pub struct CovariantRef<'a, T: ?Sized>(&'a T);
impl<'a, T: ?Sized> InvariantRef<'a, T> {
pub const fn new(r: &'a T) -> Self {
InvariantRef(r, PhantomData)
}
}
impl<'a> InvariantRef<'a, ()> {
pub const NEW: Self = InvariantRef::new(&());
}
impl<'a> CovariantRef<'a, ()> {
pub const NEW: Self = CovariantRef(&());
}
fn match_invariant_ref<'a>() {
let y = ();
match InvariantRef::new(&y) {
//~^ ERROR `y` does not live long enough [E0597]
const { InvariantRef::<'a>::NEW } => (),
}
}
fn match_covariant_ref<'a>() {
// Unclear if we should error here (should we be able to subtype the type of
// `y.0`), but using the associated const directly in the pattern also
// errors.
let y: (CovariantRef<'static, _>,) = (CovariantRef(&()),);
//~^ ERROR lifetime may not live long enough
match y.0 {
const { CovariantRef::<'a>::NEW } => (),
}
}
fn main() {
match_invariant_ref();
match_covariant_ref();
}
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