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pub trait Update<T> {
fn update(_: T) -> T;
}
pub trait UpdateRef<T> {
fn update_ref(_: &mut T);
}
impl<T, U: UpdateRef<T>> Update<T> for U {
fn update(mut t: T) -> T {
<U as UpdateRef<_>>::update_ref(&mut t);
t
}
}
#[cfg(test)]
mod test {
use super::{Update, UpdateRef};
struct Doubler;
impl<'a> Update<&'a mut u64> for Doubler {
fn update(t: &'a mut u64) -> &'a mut u64 {
Doubler::update_ref(t);
t
}
}
impl UpdateRef<u64> for Doubler {
fn update_ref(t: &mut u64) {
(*t) *= 2;
}
}
fn intercepted(foo: u64) -> u64 {
foo + 2
}
fn intercepted_ref(foo: &mut u64) {
(*foo) += 2
}
#[test]
fn test() {
fn _intercepted(foo: u64) -> u64 {
let foo = <Doubler as Update<_>>::update(foo);
intercepted(foo)
}
fn _intercepted_ref(foo: &mut u64) {
let foo = <Doubler as Update<_>>::update(foo);
intercepted_ref(foo)
}
let mut v = 42;
let r = _intercepted(v);
assert_eq!(r, 86);
_intercepted_ref(&mut v);
assert_eq!(v, 86);
}
}