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Incoming breakage: Use new auto trait syntax #1

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84 changes: 42 additions & 42 deletions src/lib.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
#![deny(missing_docs)]
#![cfg_attr(feature = "oibit", feature(optin_builtin_traits))]
#![cfg_attr(feature = "oibit", feature(auto_traits, negative_impls))]

//! A safe approach to using `#[repr(packed)]` data.
//!
Expand All @@ -9,11 +9,47 @@ use std::mem::{transmute, uninitialized, forget, align_of, size_of};
use std::ptr::write;
use std::marker::PhantomData;

/// A marker trait indicating that a type has an alignment of `1`.
///
/// In general, only applies to `()`, `bool`, `i8`, `u8`, and any types that
/// contain only members of these types.
pub unsafe trait Unaligned { }
macro_rules! define_marker_trait_unaligned {
([$($auto:ident)?] $($impl:item)*) => {
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@fmease fmease Mar 28, 2026 •
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I'm using the Kleene ? out of convenience. However, that sets the minimum supported Rust version (MSRV) to 1.37 (2019). I could replace it with Kleene * to potentially lower the MSRV if you'd like me to. I haven't investigated the MSRV of the master branch.

/// A marker trait indicating that a type has an alignment of `1`.
///
/// In general, only applies to `()`, `bool`, `i8`, `u8`, and any types that
/// contain only members of these types.
pub unsafe $($auto)? trait Unaligned { }

$($impl)*
}
}

#[cfg(not(feature = "oibit"))]
define_marker_trait_unaligned! { []
unsafe impl Unaligned for () { }
unsafe impl Unaligned for i8 { }
unsafe impl Unaligned for u8 { }
unsafe impl Unaligned for bool { }
}

#[cfg(feature = "oibit")]
define_marker_trait_unaligned! { [auto]
// All primitives except the packed ones listed above
impl !Unaligned for char { }
impl !Unaligned for f32 { }
impl !Unaligned for f64 { }
impl !Unaligned for i16 { }
impl !Unaligned for u16 { }
impl !Unaligned for i32 { }
impl !Unaligned for u32 { }
impl !Unaligned for i64 { }
impl !Unaligned for u64 { }
impl !Unaligned for isize { }
impl !Unaligned for usize { }
impl<T> !Unaligned for *const T { }
impl<T> !Unaligned for *mut T { }
impl<'a, T> !Unaligned for &'a T { }
impl<'a, T> !Unaligned for &'a mut T { }
}

unsafe impl<T> Unaligned for PhantomData<T> { }

/// A type alias that represents the unaligned type of `T`.
pub type Un<T> = <T as Aligned>::Unaligned;
Expand Down Expand Up @@ -134,42 +170,6 @@ pub unsafe trait Packed: Unaligned {
fn __assert_unaligned() { }
}

#[cfg(feature = "oibit")]
mod impls {
use super::Unaligned;

unsafe impl Unaligned for .. { }

// All primitives except the packed ones listed below
impl !Unaligned for char { }
impl !Unaligned for f32 { }
impl !Unaligned for f64 { }
impl !Unaligned for i16 { }
impl !Unaligned for u16 { }
impl !Unaligned for i32 { }
impl !Unaligned for u32 { }
impl !Unaligned for i64 { }
impl !Unaligned for u64 { }
impl !Unaligned for isize { }
impl !Unaligned for usize { }
impl<T> !Unaligned for *const T { }
impl<T> !Unaligned for *mut T { }
impl<'a, T> !Unaligned for &'a T { }
impl<'a, T> !Unaligned for &'a mut T { }
}

#[cfg(not(feature = "oibit"))]
mod impls {
use super::Unaligned;

unsafe impl Unaligned for () { }
unsafe impl Unaligned for i8 { }
unsafe impl Unaligned for u8 { }
unsafe impl Unaligned for bool { }
}

unsafe impl<T> Unaligned for PhantomData<T> { }

macro_rules! aligned_assert {
($t:ident) => {
unsafe fn __assert_unaligned() {
Expand Down