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// edition:2018
// check-pass
#![feature(type_alias_impl_trait)]
trait Trait<'a, 'b> {}
impl<T> Trait<'_, '_> for T {}
// Here we wind up selecting `'a` and `'b` in the hidden type because
// those are the types that appear in the original values.
type Foo<'a, 'b> = impl Trait<'a, 'b>;
fn upper_bounds<'a, 'b>(a: &'a u8, b: &'b u8) -> Foo<'a, 'b> {
// In this simple case, you have a hidden type `(&'0 u8, &'1 u8)` and constraints like
//
// ```
// 'a: '0
// 'b: '1
// '0 in ['a, 'b]
// '1 in ['a, 'b]
// ```
//
// We use the fact that `'a: 0'` must hold (combined with the in
// constraint) to determine that `'0 = 'a` must be the answer.
(a, b)
}
fn main() {}
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