2540070fd4
Documents that `BikeshedIntrinsicFrom` models transmute-via-union, which is slightly more expressive than the transmute-via-cast implemented by `transmute_copy`. Additionally, we provide an implementation of transmute-via-union as a method on the `BikeshedIntrinsicFrom` trait with additional documentation on the boundary between trait invariants and caller obligations. Whether or not transmute-via-union is the right kind of transmute to model remains up for discussion [1]. Regardless, it seems wise to document the present behavior. [1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20'kind'.20of.20transmute.20to.20model.3F/near/426331967
24 lines
594 B
Diff
24 lines
594 B
Diff
- // MIR for `transmute_to_ref_uninhabited` before LowerIntrinsics
|
|
+ // MIR for `transmute_to_ref_uninhabited` after LowerIntrinsics
|
|
|
|
fn transmute_to_ref_uninhabited() -> ! {
|
|
let mut _0: !;
|
|
let _1: &Never;
|
|
scope 1 {
|
|
debug x => _1;
|
|
}
|
|
|
|
bb0: {
|
|
StorageLive(_1);
|
|
- _1 = std::intrinsics::transmute::<usize, &Never>(const 1_usize) -> [return: bb1, unwind unreachable];
|
|
+ _1 = const 1_usize as &Never (Transmute);
|
|
+ goto -> bb1;
|
|
}
|
|
|
|
bb1: {
|
|
PlaceMention((*_1));
|
|
unreachable;
|
|
}
|
|
}
|
|
|