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Reduce alignment of TypeId to u64 alignment #121358

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Merged
merged 3 commits into from
Mar 9, 2024
Merged

Reduce alignment of TypeId to u64 alignment #121358

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c5aa659
Reduce alignment of TypeId to u64 alignment
GnomedDev Feb 20, 2024
aa25c48
Add extra detail to field comment
GnomedDev Feb 20, 2024
f142476
Fix Hash impl
GnomedDev Feb 25, 2024
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11 changes: 8 additions & 3 deletions library/core/src/any.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -605,7 +605,9 @@ impl dyn Any + Send + Sync {
#[derive(Clone, Copy, Debug, Eq, PartialOrd, Ord)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct TypeId {
t: u128,
// We avoid using `u128` because that imposes higher alignment requirements on many platforms.
// See issue #115620 for more information.
t: (u64, u64),
}

#[stable(feature = "rust1", since = "1.0.0")]
Expand Down Expand Up @@ -637,7 +639,10 @@ impl TypeId {
#[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
pub const fn of<T: ?Sized + 'static>() -> TypeId {
let t: u128 = intrinsics::type_id::<T>();
TypeId { t }

let t1 = (t >> 64) as u64;
let t2 = t as u64;
TypeId { t: (t1, t2) }
}
}

Expand All @@ -657,7 +662,7 @@ impl hash::Hash for TypeId {
// - It is correct to do so -- only hashing a subset of `self` is still
// with an `Eq` implementation that considers the entire value, as
// ours does.
(self.t as u64).hash(state);
self.t.1.hash(state);
}
}

Expand Down