src/test/ui/union/union-manuallydrop-rpass.rs

   1 #![feature(untagged_unions)]
   2 #![allow(dead_code)]
   3 // run-pass
   4
   5 use std::mem::needs_drop;
   6 use std::mem::ManuallyDrop;
   7
   8 struct NeedDrop;
   9
  10 impl Drop for NeedDrop {
  11     fn drop(&mut self) {}
  12 }
  13
  14 union UnionOk1<T> {
  15     empty: (),
  16     value: ManuallyDrop<T>,
  17 }
  18
  19 union UnionOk2 {
  20     value: ManuallyDrop<NeedDrop>,
  21 }
  22
  23 #[allow(dead_code)]
  24 union UnionOk3<T: Copy> {
  25     empty: (),
  26     value: T,
  27 }
  28
  29 trait Foo { }
  30
  31 trait ImpliesCopy : Copy { }
  32
  33 #[allow(dead_code)]
  34 union UnionOk4<T: ImpliesCopy> {
  35     value: T,
  36 }
  37
  38 fn main() {
  39     // NeedDrop should not make needs_drop true
  40     assert!(!needs_drop::<UnionOk1<NeedDrop>>());
  41     assert!(!needs_drop::<UnionOk3<&dyn Foo>>());
  42 }