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Auto merge of #35627 - apasel422:coerce-cell, r=alexcrichton

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Implement `CoerceUnsized` for `{Cell, RefCell, UnsafeCell}`

These impls are analogous to the one for `NonZero`. It's occasionally useful to be able to coerce the cell types when they're being used inside another abstraction. See Manishearth/rust-gc#17 for an example.

r? @eddyb
This commit is contained in:
bors 2016-08-23 04:16:28 -07:00 committed by GitHub
commit 43204fff5d
1 changed files with 16 additions and 0 deletions
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16
src/libcore/cell.rs
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@ -355,6 +355,9 @@ impl<T: Copy> From<T> for Cell<T> {
}
}
#[unstable(feature = "coerce_unsized", issue = "27732")]
impl<T: CoerceUnsized<U>, U> CoerceUnsized<Cell<U>> for Cell<T> {}
/// A mutable memory location with dynamically checked borrow rules
///
/// See the [module-level documentation](index.html) for more.
@ -793,6 +796,9 @@ impl<T> From<T> for RefCell<T> {
}
}
#[unstable(feature = "coerce_unsized", issue = "27732")]
impl<T: CoerceUnsized<U>, U> CoerceUnsized<RefCell<U>> for RefCell<T> {}
struct BorrowRef<'b> {
borrow: &'b Cell<BorrowFlag>,
}
@ -1122,3 +1128,13 @@ impl<T> From<T> for UnsafeCell<T> {
UnsafeCell::new(t)
}
}
#[unstable(feature = "coerce_unsized", issue = "27732")]
impl<T: CoerceUnsized<U>, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> {}
#[allow(unused)]
fn assert_coerce_unsized(a: UnsafeCell<&i32>, b: Cell<&i32>, c: RefCell<&i32>) {
let _: UnsafeCell<&Send> = a;
let _: Cell<&Send> = b;
let _: RefCell<&Send> = c;
}