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Express Alignment::read's pointer guarantees as a tuple #3878

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Express Alignment::read's pointer guarantees as a tuple #3878

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28 changes: 16 additions & 12 deletions zerocopy/src/pointer/invariant.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -42,13 +42,17 @@ pub trait Aliasing: Sealed {

/// The alignment invariant of a [`Ptr`][super::Ptr].
pub trait Alignment: Sealed {
// Name the aliasing parameter directly rather than quantifying over an
// Invariants implementation whose Alignment is Self. Both forms require
// the same pointer guarantees; the tuple avoids a recursive dependency
// between the Alignment and Invariants trait declarations during extraction.

@chatgpt-codex-connector chatgpt-codex-connector Bot Oct 15, 2026

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P1 Badge Wrap the comment at the repository limit

This new comment is 81 columns wide, including its prefix, although it can be wrapped without impairing readability. Move during extraction. onto a continuation line to comply with the subtree's 80-column prose convention.

AGENTS.md reference: zerocopy/AGENTS.md:L38-L40

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#[doc(hidden)]
#[must_use]
fn read<T, I, R>(ptr: crate::Ptr<'_, T, I>) -> T
fn read<T, A, R>(ptr: crate::Ptr<'_, T, (A, Self, Safe)>) -> T
where
T: Copy + Read<I::Aliasing, R>,
I: Invariants<Alignment = Self, Validity = Safe>,
I::Aliasing: Reference;
Self: Sized,
T: Copy + Read<A, R>,
A: Reference;
}

/// The validity invariant of a [`Ptr`][super::Ptr].
Expand Down Expand Up @@ -148,11 +152,11 @@ pub enum Unaligned {}

impl Alignment for Unaligned {
#[inline(always)]
fn read<T, I, R>(ptr: crate::Ptr<'_, T, I>) -> T
fn read<T, A, R>(ptr: crate::Ptr<'_, T, (A, Self, Safe)>) -> T
where
T: Copy + Read<I::Aliasing, R>,
I: Invariants<Alignment = Self, Validity = Safe>,
I::Aliasing: Reference,
Self: Sized,
T: Copy + Read<A, R>,
A: Reference,
{
(*ptr.into_unalign().as_ref()).into_inner()
}
Expand All @@ -163,11 +167,11 @@ impl Alignment for Unaligned {
pub enum Aligned {}
impl Alignment for Aligned {
#[inline(always)]
fn read<T, I, R>(ptr: crate::Ptr<'_, T, I>) -> T
fn read<T, A, R>(ptr: crate::Ptr<'_, T, (A, Self, Safe)>) -> T
where
T: Copy + Read<I::Aliasing, R>,
I: Invariants<Alignment = Self, Validity = Safe>,
I::Aliasing: Reference,
Self: Sized,
T: Copy + Read<A, R>,
A: Reference,
{
*ptr.as_ref()
}
Expand Down
2 changes: 1 addition & 1 deletion zerocopy/src/pointer/ptr.rs
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Expand Up @@ -613,7 +613,7 @@ mod _conversions {
T: Copy,
T: Read<I::Aliasing, R>,
{
<I::Alignment as Alignment>::read(self)
<I::Alignment as Alignment>::read(self.unify_invariants())
}

/// Views the value as an aligned reference.
Expand Down
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