diff options
Diffstat (limited to 'src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs')
-rw-r--r-- | src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs new file mode 100644 index 000000000..2421b24cb --- /dev/null +++ b/src/test/ui/transmutability/visibility/assume/should_accept_if_dst_has_tricky_unreachable_field.rs @@ -0,0 +1,46 @@ +// check-pass +//! Unless visibility is assumed, a transmutation should be rejected if the +//! destination type contains an unreachable field (e.g., a public field with a +//! private type). (This rule is distinct from type privacy, which still may +//! forbid naming such types.) +//! +//! This test exercises a tricky-to-implement instance of this principle: the +//! "pub-in-priv trick". In the below example, the type `dst::private::Zst` is +//! unreachable from `Context`. + +#![crate_type = "lib"] +#![feature(transmutability)] +#![allow(dead_code)] + +mod assert { + use std::mem::BikeshedIntrinsicFrom; + + pub fn is_transmutable<Src, Dst, Context>() + where + Dst: BikeshedIntrinsicFrom<Src, Context, false, false, false, true> + // visibility IS assumed -------------------------------------^^^^ + {} +} + +mod src { + #[repr(C)] pub(in super) struct Zst; + + #[repr(C)] pub(in super) struct Src { + pub(in super) field: Zst, + } +} + +mod dst { + mod private { + #[repr(C)] pub struct Zst; // <- unreachable type + } + + #[repr(C)] pub(in super) struct Dst { + pub(in super) field: private::Zst, + } +} + +fn test() { + struct Context; + assert::is_transmutable::<src::Src, dst::Dst, Context>(); +} |