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//@ revisions: current next
//@[next] compile-flags: -Znext-solver
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[current] check-pass
fn prove_proj<R>(_: impl FnOnce() -> R) {}
fn recur<'a>() -> impl Sized + 'a {
// The closure has the signature `fn() -> opaque<'1>`. `prove_proj`
// requires us to prove `<closure as FnOnce<()>>::Output = opaque<'2>`.
// The old solver uses `replace_opaque_types_with_infer` during normalization
// to replace `opaque<'2>` with its hidden type. If that hidden type is still an
// inference variable at this point, we unify it with `opaque<'1>` and
// end up ignoring that defining use as the hidden type is equal to its key.
prove_proj(|| recur());
//[next]~^ ERROR expected generic lifetime parameter, found `'_`
}
fn main() {}
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