concrete: fix infinite recursion in Policy

Author: apoelstra

src/policy/concrete.rs

@@ -146,6 +146,12 @@ impl<Pk: MiniscriptKey> ForEachKey<Pk> for Policy<Pk> {
         Pk: 'a,
         Pk::Hash: 'a,
     {
+        self.real_for_each_key(&mut pred)
+    }
+}
+
+impl<Pk: MiniscriptKey> Policy<Pk> {
+    fn real_for_each_key<'a, F: FnMut(ForEach<'a, Pk>) -> bool>(&'a self, pred: &mut F) -> bool {
         match *self {
             Policy::Unsatisfiable | Policy::Trivial => true,
             Policy::Key(ref pk) => pred(ForEach::Key(pk)),
@@ -156,9 +162,9 @@ impl<Pk: MiniscriptKey> ForEachKey<Pk> for Policy<Pk> {
             | Policy::After(..)
             | Policy::Older(..) => true,
             Policy::Threshold(_, ref subs) | Policy::And(ref subs) => {
-                subs.iter().all(|sub| sub.for_each_key(&mut pred))
+                subs.iter().all(|sub| sub.real_for_each_key(&mut *pred))
             }
-            Policy::Or(ref subs) => subs.iter().all(|(_, sub)| sub.for_each_key(&mut pred)),
+            Policy::Or(ref subs) => subs.iter().all(|(_, sub)| sub.real_for_each_key(&mut *pred)),
         }
     }
 }
@@ -654,3 +660,19 @@ where
         Policy::from_tree_prob(top, false).map(|(_, result)| result)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::str::FromStr;
+
+    #[test]
+    fn for_each_key() {
+        let liquid_pol = Policy::<String>::from_str(
+            "or(and(older(4096),thresh(2,pk(A),pk(B),pk(C))),thresh(11,pk(F1),pk(F2),pk(F3),pk(F4),pk(F5),pk(F6),pk(F7),pk(F8),pk(F9),pk(F10),pk(F11),pk(F12),pk(F13),pk(F14)))").unwrap();
+        let mut count = 0;
+        assert!(liquid_pol.for_each_key(|_| { count +=1; true }));
+        assert_eq!(count, 17);
+    }
+}
+