Remove ChainBehavior.

src/parser/exiting.rs

@@ -9,3 +9,9 @@ pub enum ExitClass {
     /// Elements who cede priority to alpha elements when matching.
     Beta = 300,
 }
+
+impl std::fmt::Display for ExitClass {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}