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

28 lines
905 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 covariant with respect to 'a, meaning that
// Covariant<'foo> <: Covariant<'static> because
// 'foo <= 'static
struct Covariant<'a> {
f: extern "Rust" fn(&'a isize)
}
fn use_<'short,'long>(c: Covariant<'long>,
s: &'short isize,
l: &'long isize,
_where:Option<&'short &'long ()>) {
// Test whether Covariant<'long> <: Covariant<'short>. Since
// 'short <= 'long, this would be true if the Covariant type were
// contravariant with respect to its parameter 'a.
let _: Covariant<'short> = c;
//~^ ERROR lifetime may not live long enough
}
fn main() {}