Move the EmacsField enum since it has nothing to do with ElispFact.

src/compare/macros.rs

@@ -1,3 +1,9 @@
+#[derive(Debug)]
+pub(crate) enum EmacsField<'s> {
+    Required(&'s str),
+    Optional(&'s str),
+}
+
 /// Create iterators for ast nodes where it only has to iterate over children
 macro_rules! compare_properties {
     ($emacs:expr, $($emacs_field:expr, $rust_value:expr, $compare_fn: ident),+) => {