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//@ run-pass
#![allow(dead_code)]
use std::ops::Deref;
struct DerefWithHelper<H, T> {
helper: H,
value: T
}
trait Helper<T> {
fn helper_borrow(&self) -> &T;
}
impl<T> Helper<T> for Option<T> {
fn helper_borrow(&self) -> &T {
self.as_ref().unwrap()
}
}
impl<T, H: Helper<T>> Deref for DerefWithHelper<H, T> {
type Target = T;
fn deref(&self) -> &T {
self.helper.helper_borrow()
}
}
struct Foo {x: isize}
impl Foo {
fn foo(&self) -> isize {self.x}
}
pub fn main() {
let x: DerefWithHelper<Option<Foo>, Foo> =
DerefWithHelper { helper: Some(Foo {x: 5}), value: Foo { x: 2 } };
assert_eq!(x.foo(), 5);
}
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