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