1 #![allow(deprecated, invalid_value)]
6 fn might_panic<X>(x: X) -> X {
7 // in practice this would be a possibly-panicky operation
12 let mut v = vec![0i32; 4];
13 // the following is UB if `might_panic` panics
15 let taken_v = mem::replace(&mut v, mem::uninitialized());
16 let new_v = might_panic(taken_v);
17 std::mem::forget(mem::replace(&mut v, new_v));
21 let taken_v = mem::replace(&mut v, mem::MaybeUninit::uninit().assume_init());
22 let new_v = might_panic(taken_v);
23 std::mem::forget(mem::replace(&mut v, new_v));
27 let taken_v = mem::replace(&mut v, mem::zeroed());
28 let new_v = might_panic(taken_v);
29 std::mem::forget(mem::replace(&mut v, new_v));
32 // this is silly but OK, because usize is a primitive type
33 let mut u: usize = 42;
35 let taken_u = unsafe { mem::replace(uref, mem::zeroed()) };
38 // this is still not OK, because uninit
39 let taken_u = unsafe { mem::replace(uref, mem::uninitialized()) };