Debug impl for OrderedSet

Author: dtolnay

syntax/set.rs

@@ -1,4 +1,5 @@
 use std::collections::HashSet;
+use std::fmt::{self, Debug};
 use std::hash::Hash;
 use std::slice;
 
@@ -47,3 +48,12 @@ impl<'s, 'a, T> Iterator for Iter<'s, 'a, T> {
         self.0.next().copied()
     }
 }
+
+impl<'a, T> Debug for OrderedSet<&'a T>
+where
+    T: Debug,
+{
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.debug_set().entries(self).finish()
+    }
+}