bjoernager/rust
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Fallout: btree. Rephrase invariant lifetime in terms of PhantomData.

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This commit is contained in:
Niko Matsakis 2015-02-12 10:33:53 -05:00
parent c5579ca340
commit b3c00a69f2
1 changed files with 13 additions and 4 deletions
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17
src/libcollections/btree/map.rs
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@ -512,13 +512,22 @@ mod stack {
use super::super::node::handle; use super::super::node::handle;
use vec::Vec; use vec::Vec;
struct InvariantLifetime<'id>(
marker::PhantomData<::core::cell::Cell<&'id ()>>);
impl<'id> InvariantLifetime<'id> {
fn new() -> InvariantLifetime<'id> {
InvariantLifetime(marker::PhantomData)
}
}
/// A generic mutable reference, identical to `&mut` except for the fact that its lifetime /// A generic mutable reference, identical to `&mut` except for the fact that its lifetime
/// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef` /// parameter is invariant. This means that wherever an `IdRef` is expected, only an `IdRef`
/// with the exact requested lifetime can be used. This is in contrast to normal references, /// with the exact requested lifetime can be used. This is in contrast to normal references,
/// where `&'static` can be used in any function expecting any lifetime reference. /// where `&'static` can be used in any function expecting any lifetime reference.
pub struct IdRef<'id, T: 'id> { pub struct IdRef<'id, T: 'id> {
inner: &'id mut T, inner: &'id mut T,
marker: marker::InvariantLifetime<'id> _marker: InvariantLifetime<'id>,
} }
impl<'id, T> Deref for IdRef<'id, T> { impl<'id, T> Deref for IdRef<'id, T> {
@ -560,7 +569,7 @@ mod stack {
pub struct Pusher<'id, 'a, K:'a, V:'a> { pub struct Pusher<'id, 'a, K:'a, V:'a> {
map: &'a mut BTreeMap<K, V>, map: &'a mut BTreeMap<K, V>,
stack: Stack<K, V>, stack: Stack<K, V>,
marker: marker::InvariantLifetime<'id> _marker: InvariantLifetime<'id>,
} }
impl<'a, K, V> PartialSearchStack<'a, K, V> { impl<'a, K, V> PartialSearchStack<'a, K, V> {
@ -595,11 +604,11 @@ mod stack {
let pusher = Pusher { let pusher = Pusher {
map: self.map, map: self.map,
stack: self.stack, stack: self.stack,
marker: marker::InvariantLifetime _marker: InvariantLifetime::new(),
}; };
let node = IdRef { let node = IdRef {
inner: unsafe { &mut *self.next }, inner: unsafe { &mut *self.next },
marker: marker::InvariantLifetime _marker: InvariantLifetime::new(),
}; };
closure(pusher, node) closure(pusher, node)