Using a mutable reference breaks clone.

src/parser/text_element_parser.rs

@@ -25,5 +25,6 @@ fn flat_text_element<'s, 'r>(
     i: &'s str,
     context: &'r mut NomContext,
 ) -> Res<&'s str, TextElement<'s>> {
+    not(&mut context.fail_matcher)(i)?;
     todo!()
 }