1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
|
//@ run-pass
// Test that vec is now covariant in its argument type.
#![allow(dead_code)]
fn foo<'a,'b>(v1: Vec<&'a i32>, v2: Vec<&'b i32>) -> i32 {
bar(v1, v2).cloned().unwrap_or(0) // only type checks if we can intersect 'a and 'b
}
fn bar<'c>(v1: Vec<&'c i32>, v2: Vec<&'c i32>) -> Option<&'c i32> {
v1.get(0).cloned().or_else(|| v2.get(0).cloned())
}
fn main() {
let x = 22;
let y = 44;
assert_eq!(foo(vec![&x], vec![&y]), 22);
assert_eq!(foo(vec![&y], vec![&x]), 44);
}
|
