| // check-fail |
| // known-bug: #87735, #88526 |
| |
| // This should pass, but we need an extension of implied bounds (probably). |
| |
| pub trait AsRef2 { |
| type Output<'a> where Self: 'a; |
| |
| fn as_ref2<'a>(&'a self) -> Self::Output<'a>; |
| } |
| |
| impl<T> AsRef2 for Vec<T> { |
| type Output<'a> = &'a [T] where Self: 'a; |
| |
| fn as_ref2<'a>(&'a self) -> Self::Output<'a> { |
| &self[..] |
| } |
| } |
| |
| #[derive(Debug)] |
| struct Foo<T>(T); |
| #[derive(Debug)] |
| struct FooRef<'a, U>(&'a [U]); |
| |
| impl<'b, T, U> AsRef2 for Foo<T> |
| where |
| // * `for<'b, 'c> T: AsRef2<Output<'b> = &'c [U]>>` does not work |
| // |
| // * `U` is unconstrained but should be allowed in this context because `Output` is |
| // an associated type |
| T: AsRef2<Output<'b> = &'b [U]>, |
| U: 'b |
| { |
| type Output<'a> = FooRef<'a, U> where Self: 'a; |
| |
| fn as_ref2<'a>(&'a self) -> Self::Output<'a> { |
| FooRef(self.0.as_ref2()) |
| } |
| } |
| |
| fn main() { |
| let foo = Foo(vec![1, 2, 3]); |
| dbg!(foo.as_ref2()); |
| } |