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// run-pass
// Regression test for issue #47139:
//
// Coherence was encountering an (unnecessary) overflow trying to
// decide if the two impls of dummy overlap.
//
// The overflow went something like:
//
// - `&'a ?T: Insertable` ?
// - let ?T = Option<?U> ?
// - `Option<?U>: Insertable` ?
// - `Option<&'a ?U>: Insertable` ?
// - `&'a ?U: Insertable` ?
//
// While somewhere in the middle, a projection would occur, which
// broke cycle detection.
//
// It turned out that this cycle was being kicked off due to some
// extended diagnostic attempts in coherence, so removing those
// sidestepped the issue for now.
#![allow(dead_code)]
pub trait Insertable {
type Values;
fn values(self) -> Self::Values;
}
impl<T> Insertable for Option<T>
where
T: Insertable,
T::Values: Default,
{
type Values = T::Values;
fn values(self) -> Self::Values {
self.map(Insertable::values).unwrap_or_default()
}
}
impl<'a, T> Insertable for &'a Option<T>
where
Option<&'a T>: Insertable,
{
type Values = <Option<&'a T> as Insertable>::Values;
fn values(self) -> Self::Values {
self.as_ref().values()
}
}
impl<'a, T> Insertable for &'a [T]
{
type Values = Self;
fn values(self) -> Self::Values {
self
}
}
trait Unimplemented { }
trait Dummy { }
struct Foo<T> { t: T }
impl<'a, U> Dummy for Foo<&'a U>
where &'a U: Insertable
{
}
impl<T> Dummy for T
where T: Unimplemented
{ }
fn main() {
}
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