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Rollup merge of #94991 - CAD97:const-weak-new, r=dtolnay

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Make Weak::new const

Simple enough. This is const creation of an allocating container, but no actual allocation is done, because it's defined to.
This commit is contained in:
Dylan DPC 2022-03-19 14:50:25 +01:00 committed by GitHub
commit 6a73024661
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2 changed files with 6 additions and 4 deletions
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5
library/alloc/src/rc.rs
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@ -2112,9 +2112,10 @@ impl<T> Weak<T> {
/// assert!(empty.upgrade().is_none());
/// ```
#[stable(feature = "downgraded_weak", since = "1.10.0")]
#[rustc_const_unstable(feature = "const_weak_new", issue = "95091", reason = "recently added")]
#[must_use]
pub fn new() -> Weak<T> {
Weak { ptr: NonNull::new(usize::MAX as *mut RcBox<T>).expect("MAX is not 0") }
pub const fn new() -> Weak<T> {
Weak { ptr: unsafe { NonNull::new_unchecked(usize::MAX as *mut RcBox<T>) } }
}
}

5
library/alloc/src/sync.rs
View File

@ -1742,9 +1742,10 @@ impl<T> Weak<T> {
/// assert!(empty.upgrade().is_none());
/// ```
#[stable(feature = "downgraded_weak", since = "1.10.0")]
#[rustc_const_unstable(feature = "const_weak_new", issue = "95091", reason = "recently added")]
#[must_use]
pub fn new() -> Weak<T> {
Weak { ptr: NonNull::new(usize::MAX as *mut ArcInner<T>).expect("MAX is not 0") }
pub const fn new() -> Weak<T> {
Weak { ptr: unsafe { NonNull::new_unchecked(usize::MAX as *mut ArcInner<T>) } }
}
}