make it possible to clone a UnificationTable

Author: nikomatsakis

src/snapshot_vec.rs

@@ -223,3 +223,29 @@ impl<D: SnapshotVecDelegate> ops::IndexMut<usize> for SnapshotVec<D> {
         self.get_mut(index)
     }
 }
+
+impl<D: SnapshotVecDelegate> Clone for SnapshotVec<D>
+    where D::Value: Clone, D::Undo: Clone,
+{
+    fn clone(&self) -> Self {
+        SnapshotVec {
+            values: self.values.clone(),
+            undo_log: self.undo_log.clone(),
+        }
+    }
+}
+
+impl<D: SnapshotVecDelegate> Clone for UndoLog<D>
+    where D::Value: Clone, D::Undo: Clone,
+{
+    fn clone(&self) -> Self {
+        match *self {
+            OpenSnapshot => OpenSnapshot,
+            CommittedSnapshot => CommittedSnapshot,
+            NewElem(i) => NewElem(i),
+            SetElem(i, ref v) => SetElem(i, v.clone()),
+            Other(ref u) => Other(u.clone()),
+        }
+    }
+}
+

src/unify/mod.rs

@@ -85,6 +85,7 @@ struct VarValue<K: UnifyKey> {
 }
 
 /// Table of unification keys and their values.
+#[derive(Clone)]
 pub struct UnificationTable<K: UnifyKey> {
     /// Indicates the current value of each key.
     values: sv::SnapshotVec<Delegate<K>>,

src/unify/tests.rs

@@ -317,3 +317,17 @@ fn ordered_key_k1() {
     assert!(vec![k1_5, k1_6].contains(&ut.find(k0_1)),
             "unexpected choice for root: {:?}", ut.find(k0_1));
 }
+
+/// Test that we *can* clone.
+#[test]
+fn clone_table() {
+    let mut ut: UnificationTable<IntKey> = UnificationTable::new();
+    let k1 = ut.new_key(None);
+    let k2 = ut.new_key(None);
+    assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+    assert!(ut.unify_var_value(k2, Some(22)).is_ok());
+    assert!(ut.unify_var_var(k1, k2).is_ok());
+
+    let mut ut1 = ut.clone();
+    assert_eq!(ut1.probe_value(k1), Some(22));
+}