rust/tests/ui/regions/regions-fn-subtyping.rs
2024-02-16 20:02:50 +00:00

31 lines
877 B
Rust

//@ run-pass
#![allow(dead_code)]
#![allow(unused_assignments)]
// Issue #2263.
//@ pretty-expanded FIXME #23616
#![allow(unused_variables)]
// Should pass region checking.
fn ok(f: Box<dyn FnMut(&usize)>) {
// Here, g is a function that can accept a usize pointer with
// lifetime r, and f is a function that can accept a usize pointer
// with any lifetime. The assignment g = f should be OK (i.e.,
// f's type should be a subtype of g's type), because f can be
// used in any context that expects g's type. But this currently
// fails.
let mut g: Box<dyn for<'r> FnMut(&'r usize)> = Box::new(|x| { });
g = f;
}
// This version is the same as above, except that here, g's type is
// inferred.
fn ok_inferred(f: Box<dyn FnMut(&usize)>) {
let mut g: Box<dyn for<'r> FnMut(&'r usize)> = Box::new(|_| {});
g = f;
}
pub fn main() {
}