src/test/ui/transmutability/visibility/should_reject_if_dst_has_private_variant.rs

   1 //! Unless visibility is assumed, a transmutation should be rejected if the
   2 //! destination type contains a private variant.
   3
   4 #![crate_type = "lib"]
   5 #![feature(transmutability)]
   6 #![allow(dead_code)]
   7
   8 mod assert {
   9     use std::mem::BikeshedIntrinsicFrom;
  10
  11     pub fn is_transmutable<Src, Dst, Context>()
  12     where
  13         Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, false>
  14         // visibility is NOT assumed ---------------------------------^^^^^
  15     {}
  16 }
  17
  18 mod src {
  19     #[repr(C)] pub(in super) struct Zst;
  20
  21     #[repr(C)] pub(in super) struct Src {
  22         pub(in super) field: Zst,
  23     }
  24 }
  25
  26 mod dst {
  27     #[derive(Copy, Clone)]
  28     #[repr(C)] pub(in super) struct Zst;
  29
  30     #[repr(C)] pub(in super) union Dst {
  31         pub(self) field: Zst, // <- private variant
  32     }
  33 }
  34
  35 fn test() {
  36     struct Context;
  37     assert::is_transmutable::<src::Src, dst::Dst, Context>(); //~ ERROR cannot be safely transmuted
  38 }