mirror of https://github.com/rust-lang/rust
41 lines
1.2 KiB
Rust
41 lines
1.2 KiB
Rust
//@ run-pass
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#![allow(dead_code)]
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//@ pretty-expanded FIXME #23616
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use std::rc::Rc;
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fn lub_short<'a, T>(_: &[&'a T], _: &[&'a T]) {}
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// The two arguments are a subtype of their LUB, after coercion.
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fn long_and_short<'a, T>(xs: &[&'static T; 1], ys: &[&'a T; 1]) {
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lub_short(xs, ys);
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}
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// The argument coerces to a subtype of the return type.
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fn long_to_short<'a, 'b, T>(xs: &'b [&'static T; 1]) -> &'b [&'a T] {
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xs
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}
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// Rc<T> is covariant over T just like &T.
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fn long_to_short_rc<'a, T>(xs: Rc<[&'static T; 1]>) -> Rc<[&'a T]> {
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xs
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}
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// LUB-coercion (if-else/match/array) coerces `xs: &'b [&'static T: N]`
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// to a subtype of the LUB of `xs` and `ys` (i.e., `&'b [&'a T]`),
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// regardless of the order they appear (in if-else/match/array).
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fn long_and_short_lub1<'a, 'b, T>(xs: &'b [&'static T; 1], ys: &'b [&'a T]) {
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let _order1 = [xs, ys];
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let _order2 = [ys, xs];
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}
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// LUB-coercion should also have the exact same effect when `&'b [&'a T; N]`
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// needs to be coerced, i.e., the resulting type is not &'b [&'static T], but
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// rather the `&'b [&'a T]` LUB.
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fn long_and_short_lub2<'a, 'b, T>(xs: &'b [&'static T], ys: &'b [&'a T; 1]) {
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let _order1 = [xs, ys];
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let _order2 = [ys, xs];
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}
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fn main() {}
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