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TryFromBytes for MaybeUninit<T> requires T: NoCell #889

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Merged
joshlf merged 1 commit into from
Feb 16, 2024
Merged

TryFromBytes for MaybeUninit<T> requires T: NoCell #889

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10 changes: 6 additions & 4 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3502,13 +3502,15 @@ safety_comment! {
/// - `NoCell`: `MaybeUninit<T>` has `UnsafeCell`s exactly when `T` does, so
/// `T: NoCell` guarantees that `MaybeUninit<T>` has no `UnsafeCell`s.
/// - `TryFromBytes` (with no validator), `FromZeros`, `FromBytes`:
/// `MaybeUninit<T>` has no restrictions on its contents.
/// `MaybeUninit<T>` has no restrictions on its contents. `TryFromBytes`
/// may not be implemented for types which contain `UnsafeCell`, which we
/// satisfy thanks to the `T: NoCell` bound.
/// - `Unaligned`: "MaybeUninit<T> is guaranteed to have the same size,
/// alignment, and ABI as T" [1]
///
/// [1] https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#layout-1
unsafe_impl!(T: NoCell => NoCell for MaybeUninit<T>);
unsafe_impl!(T => TryFromBytes for MaybeUninit<T>);
unsafe_impl!(T: NoCell => TryFromBytes for MaybeUninit<T>);
unsafe_impl!(T => FromZeros for MaybeUninit<T>);
unsafe_impl!(T => FromBytes for MaybeUninit<T>);
unsafe_impl!(T: Unaligned => Unaligned for MaybeUninit<T>);
Expand Down Expand Up @@ -8429,8 +8431,8 @@ mod tests {
assert_impls!(ManuallyDrop<[UnsafeCell<()>]>: KnownLayout, FromZeros, FromBytes, IntoBytes, Unaligned, !NoCell, !TryFromBytes);

assert_impls!(MaybeUninit<u8>: KnownLayout, NoCell, TryFromBytes, FromZeros, FromBytes, Unaligned, !IntoBytes);
assert_impls!(MaybeUninit<NotZerocopy>: KnownLayout, TryFromBytes, FromZeros, FromBytes, !NoCell, !IntoBytes, !Unaligned);
assert_impls!(MaybeUninit<UnsafeCell<()>>: KnownLayout, TryFromBytes, FromZeros, FromBytes, Unaligned, !NoCell, !IntoBytes);
assert_impls!(MaybeUninit<NotZerocopy>: KnownLayout, FromZeros, FromBytes, !NoCell, !TryFromBytes, !IntoBytes, !Unaligned);
assert_impls!(MaybeUninit<UnsafeCell<()>>: KnownLayout, FromZeros, FromBytes, Unaligned, !TryFromBytes, !NoCell, !IntoBytes);

assert_impls!(Wrapping<u8>: KnownLayout, NoCell, TryFromBytes, FromZeros, FromBytes, IntoBytes, Unaligned);
assert_impls!(Wrapping<NotZerocopy>: KnownLayout, !NoCell, !TryFromBytes, !FromZeros, !FromBytes, !IntoBytes, !Unaligned);
Expand Down