Partially implement VM

The following are now implemented:

- [x] Arrow
- [x] StringKey
- [x] RegexKey
- [ ] KeySubtree
- [ ] ValueSubtree
- [x] Ident
- [ ] Param
- [x] ApplyPredicate
- [x] End

1 files changed, 9 insertions, 0 deletions

diff --git a/src/parser.rs b/src/parser.rs
index 00fbcb1..eb54c86 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -623,6 +623,15 @@ mod tests {
         ) -> bool {
             false
         }
+
+        fn as_str<'b>(
+            item: RefOwn<'b, Self::Ref, Self::Own>
+        ) -> Option<&'b str> {
+            match item {
+                RefOwn::Str(key) => Some(key),
+                _ => None,
+            }
+        }
     }
 
     #[test]