tests/ui/issues/issue-36278-prefix-nesting.rs

   1 // run-pass
   2 // Issue 36278: On an unsized struct with >1 level of nontrivial
   3 // nesting, ensure we are computing dynamic size of prefix correctly.
   4
   5 use std::mem;
   6
   7 const SZ: usize = 100;
   8 #[allow(unused_tuple_struct_fields)]
   9 struct P<T: ?Sized>([u8; SZ], T);
  10
  11 type Ack<T> = P<P<T>>;
  12
  13 fn main() {
  14     let size_of_sized; let size_of_unsized;
  15     let x: Box<Ack<[u8; 0]>> = Box::new(P([0; SZ], P([0; SZ], [0; 0])));
  16     size_of_sized = mem::size_of_val::<Ack<_>>(&x);
  17     let y: Box<Ack<[u8   ]>> = x;
  18     size_of_unsized = mem::size_of_val::<Ack<_>>(&y);
  19     assert_eq!(size_of_sized, size_of_unsized);
  20 }