mirror of https://github.com/rust-lang/rust
39 lines
791 B
Rust
39 lines
791 B
Rust
// This is a regression test for issue #114221.
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// Check that we compute variances for lazy type aliases.
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//@ check-pass
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#![feature(lazy_type_alias)]
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#![allow(incomplete_features)]
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// [+] `A` is covariant over `'a`.
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struct A<'a>(Co<'a>);
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// [+] `Co` is covariant over `'a`.
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type Co<'a> = &'a ();
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fn co<'a>(x: A<'static>) {
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let _: A<'a> = x;
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}
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// [-] `B` is contravariant over `'a`.
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struct B<'a>(Contra<'a>);
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// [-] `Contra` is contravariant over `'a`.
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type Contra<'a> = fn(&'a ());
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fn contra<'a>(x: B<'a>) {
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let _: B<'static> = x;
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}
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struct C<T, U>(CoContra<T, U>);
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// [+, -] `CoContra` is covariant over `T` and contravariant over `U`.
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type CoContra<T, U> = Option<(T, fn(U))>;
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fn co_contra<'a>(x: C<&'static (), &'a ()>) -> C<&'a (), &'static ()> {
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x
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}
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fn main() {}
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