26 lines
656 B
Rust
26 lines
656 B
Rust
// run-pass
|
|
// Elaborated version of the opening example from RFC 738. This failed
|
|
// to compile before variance because invariance of `Option` prevented
|
|
// us from approximating the lifetimes of `field1` and `field2` to a
|
|
// common intersection.
|
|
|
|
#![allow(dead_code)]
|
|
|
|
struct List<'l> {
|
|
field1: &'l i32,
|
|
field2: Option<&'l i32>,
|
|
}
|
|
|
|
fn foo(field1: &i32, field2: Option<&i32>) -> i32 {
|
|
let list = List { field1: field1, field2: field2 };
|
|
*list.field1 + list.field2.cloned().unwrap_or(0)
|
|
}
|
|
|
|
fn main() {
|
|
let x = 22;
|
|
let y = Some(3);
|
|
let z = None;
|
|
assert_eq!(foo(&x, y.as_ref()), 25);
|
|
assert_eq!(foo(&x, z.as_ref()), 22);
|
|
}
|