mirror of https://github.com/rust-lang/rust
39 lines
1.2 KiB
Rust
39 lines
1.2 KiB
Rust
// `Opaque<'?1> := u8` is not a valid defining use here.
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//
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// Due to fundamental limitations of the member constraints algorithm,
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// we require '?1 to be *equal* to some universal region.
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//
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// While '?1 is eventually inferred to be equal to 'x because of the constraint '?1: 'x,
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// we don't consider them equal in the strict sense because they lack the bidirectional outlives
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// constraints ['?1: 'x, 'x: '?1]. In NLL terms, they are not part of the same SCC.
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//
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// See #113971 for details.
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//@ revisions: basic member_constraints
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#![feature(type_alias_impl_trait)]
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trait Captures<'a> {}
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impl<T> Captures<'_> for T {}
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fn ensure_outlives<'a, X: 'a>(_: X) {}
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fn relate<X>(_: X, _: X) {}
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type Opaque<'a> = impl Copy + Captures<'a>;
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fn test<'x>(_: Opaque<'x>) {
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let opaque = None::<Opaque<'_>>; // let's call this lifetime '?1
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#[cfg(basic)]
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let hidden = None::<u8>;
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#[cfg(member_constraints)]
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let hidden = None::<&'x u8>;
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ensure_outlives::<'x>(opaque); // outlives constraint: '?1: 'x
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relate(opaque, hidden); // defining use: Opaque<'?1> := u8
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//[basic]~^ ERROR expected generic lifetime parameter, found `'_`
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//[member_constraints]~^^ ERROR captures lifetime that does not appear in bounds
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}
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fn main() {}
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