bjoernager/rust
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Use transmute_unchecked and make the types explicit in query type erasure

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This doesn't really change anything, but makes the code a bit more explicit/readable.
This commit is contained in:
Maybe Waffle 2023-10-03 21:12:23 +00:00
parent a6dfd89fa7
commit 61361bb212
1 changed files with 4 additions and 3 deletions
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7
compiler/rustc_middle/src/query/erase.rs
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@ -2,7 +2,8 @@ use crate::mir;
use crate::query::CyclePlaceholder;
use crate::traits;
use crate::ty::{self, Ty};
use std::mem::{size_of, transmute_copy, MaybeUninit};
use std::mem::{size_of, MaybeUninit};
use std::intrinsics::transmute_unchecked;
#[derive(Copy, Clone)]
pub struct Erased<T: Copy> {
@ -30,7 +31,7 @@ pub fn erase<T: EraseType>(src: T) -> Erase<T> {
Erased::<<T as EraseType>::Result> {
// SAFETY: It is safe to transmute to MaybeUninit for types with the same sizes.
data: unsafe { transmute_copy(&src) },
data: unsafe { transmute_unchecked::<T, MaybeUninit<T::Result>>(src) },
}
}
@ -41,7 +42,7 @@ pub fn restore<T: EraseType>(value: Erase<T>) -> T {
// SAFETY: Due to the use of impl Trait in `Erase` the only way to safely create an instance
// of `Erase` is to call `erase`, so we know that `value.data` is a valid instance of `T` of
// the right size.
unsafe { transmute_copy(&value.data) }
unsafe { transmute_unchecked::<MaybeUninit<T::Result>, T>(value.data) }
}
impl<T> EraseType for &'_ T {