rust/tests/ui/regions/regions-variance-contravariant-use-covariant.rs
2023-01-11 09:32:08 +00:00

28 lines
915 B
Rust

// Test that a type which is covariant with respect to its region
// parameter yields an error when used in a contravariant way.
//
// Note: see variance-regions-*.rs for the tests that check that the
// variance inference works in the first place.
// This is contravariant with respect to 'a, meaning that
// Contravariant<'long> <: Contravariant<'short> iff
// 'short <= 'long
struct Contravariant<'a> {
f: &'a isize
}
fn use_<'short,'long>(c: Contravariant<'short>,
s: &'short isize,
l: &'long isize,
_where:Option<&'short &'long ()>) {
// Test whether Contravariant<'short> <: Contravariant<'long>. Since
// 'short <= 'long, this would be true if the Contravariant type were
// covariant with respect to its parameter 'a.
let _: Contravariant<'long> = c;
//~^ ERROR lifetime may not live long enough
}
fn main() {}