Trait selfref::Opaque

source · [−]
pub unsafe trait Opaque {
    type Kind<'a>: SelfRef<'a>
    where
        Self: 'a;
}
Expand description

An opaqueified self-referential struct “key”.

Safety

This is unsafe because there are a bunch of soundness invariants that need to be upheld. The following list is non-exhaustive:

  • Kind must not have a Drop impl in any “path” that may trace back to the original self-referential type, if said Drop impl can observe the self-referential type.
  • We assume Kind has the same layout for any 'a. This is true as of the time of writing this, and relies on Rust not having lifetime specialization.

Examples

#![feature(generic_associated_types)]

use core::cell::Cell;
 
use selfref::SelfRef;
use selfref::Opaque;

struct Foo<'a> {
    foo: Cell<Option<&'a Foo<'a>>>,
}
impl<'a> SelfRef<'a> for Foo<'a> {}

struct FooKey;
// SAFETY: Foo has no Drop impl and has the same layout for any 'a.
unsafe impl Opaque for FooKey {
    type Kind<'a> = Foo<'a>;
}

Required Associated Types

The actual self-referential struct.

Implementors