feat: Implement weak-table traits

Cargo.toml

@@ -25,6 +25,7 @@ features = ["unstable_docrs"]
 [features]
 with_ahash = ["ahash"]
 unstable_docrs = ["with_ahash"]
+weak-table = ["dep:weak-table"]
 
 [dependencies]
 lazy_static = "1.*"
@@ -33,6 +34,10 @@ lazy_static = "1.*"
 version = "^0.8.3"
 optional = true
 
+[dependencies.weak-table]
+version = "^0.3.0"
+optional = true
+
 [dev-dependencies]
 crossbeam-utils = "^0.8"
 trybuild = "^1.0"

src/lib.rs

@@ -239,7 +239,7 @@
 /// - `$hash_builder:expr` optional hash builder, an
 ///   implementation of [`std::hash::BuildHasher`] ;
 /// - `$typ:typ,` type being hashconsed (the underlying type, not the
 ///     hashconsed one) ;
 #[macro_export]
 macro_rules! consign {
     (
@@ -350,7 +350,7 @@
     }
 }
 impl<T> Eq for HConsed<T> {}
 impl<T> PartialOrd for HConsed<T> {
     #[inline]
     fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
         self.uid.partial_cmp(&other.uid)
@@ -455,6 +455,39 @@
     }
 }
 
+#[cfg(feature = "weak-table")]
+use weak_table::traits::{WeakElement, WeakKey};
+
+#[cfg(feature = "weak-table")]
+impl<T> WeakElement for WHConsed<T> {
+    type Strong = HConsed<T>;
+    fn new(x: &Self::Strong) -> Self {
+        x.to_weak()
+    }
+    fn view(&self) -> Option<Self::Strong> {
+        self.to_hconsed()
+    }
+    fn is_expired(&self) -> bool {
+        self.elm.is_expired()
+    }
+    fn clone(x: &Self::Strong) -> Self::Strong
+    where
+        Self: Sized,
+    {
+        x.clone()
+    }
+}
+#[cfg(feature = "weak-table")]
+impl<T: std::hash::Hash + Eq> WeakKey for WHConsed<T> {
+    type Key = T;
+    fn with_key<F, R>(view: &Self::Strong, f: F) -> R
+    where
+        F: FnOnce(&Self::Key) -> R,
+    {
+        f(view)
+    }
+}
+
 /// The consign storing the actual hash consed elements as `HConsed`s.
 pub struct HConsign<T: Hash + Eq + Clone, S = RandomState> {
     /// The actual hash consing table.