src/test/ui/union/union-drop-assign.rs

   1 // run-pass
   2 #![allow(unused_assignments)]
   3
   4 // Drop works for union itself.
   5
   6 use std::mem::ManuallyDrop;
   7
   8 struct S;
   9
  10 union U {
  11     a: ManuallyDrop<S>
  12 }
  13
  14 impl Drop for S {
  15     fn drop(&mut self) {
  16         unsafe { CHECK += 10; }
  17     }
  18 }
  19
  20 impl Drop for U {
  21     fn drop(&mut self) {
  22         unsafe { CHECK += 1; }
  23     }
  24 }
  25
  26 static mut CHECK: u8 = 0;
  27
  28 fn main() {
  29     unsafe {
  30         let mut u = U { a: ManuallyDrop::new(S) };
  31         assert_eq!(CHECK, 0);
  32         u = U { a: ManuallyDrop::new(S) };
  33         assert_eq!(CHECK, 1); // union itself is assigned, union is dropped, field is not dropped
  34         *u.a = S;
  35         assert_eq!(CHECK, 11); // union field is assigned, field is dropped
  36     }
  37 }