fix printing for keywords

src/symbol.rs

@@ -103,6 +103,11 @@ impl Symbol {
         Self::new_from_vec(path, true)
     }
 
+    #[inline]
+    pub fn set_as_keyword(&mut self) {
+        self.keyword = true;
+    }
+
     /// Creates a new Symbol with the path extended by the given vector of path segments.
     pub fn extend<A: AsRef<str>>(&self, child: &[A]) -> Self {
         let mut path = Vec::with_capacity(self.path.len() + child.len());

src/writer.rs

@@ -75,7 +75,8 @@ impl<F: LurkField> Write<F> for Expression<F> {
             }
             Key(car, cdr) => {
                 let head = store.fetch_string(car).expect("missing keyword head");
-                let tail = store.fetch_key(cdr).expect("missing keyword tail");
+                let mut tail = store.fetch_sym(cdr).expect("missing keyword tail");
+                tail.set_as_keyword();
                 write_symbol(w, tail.extend(&[head]), state)
             }
             EmptyStr => write!(w, "\"\""),
@@ -378,4 +379,12 @@ pub mod test {
         let res = num.fmt_to_string(&store, initial_lurk_state());
         assert_eq!(&res, &"5");
     }
+
+    #[test]
+    fn test_print_keyword() {
+        let mut store = Store::<Fr>::default();
+        let foo_key_ptr = store.intern_symbol(&Symbol::key_from_vec(vec!["foo".into()]));
+        let foo_key_str = foo_key_ptr.fmt_to_string(&store, initial_lurk_state());
+        assert_eq!(":foo", foo_key_str);
+    }
 }