Add with_additional_fail_matcher.

src/parser/new_context.rs

@@ -46,11 +46,11 @@ pub trait ContextElement {
     fn get_fail_matcher<'r>(&'r self) -> ChainBehavior<'r>;
 }
 
-struct FailMatcherNode<'r> {
+pub struct FailMatcherNode<'r> {
     fail_matcher: ChainBehavior<'r>,
 }
 
-struct PreviousElementNode<'r> {
+pub struct PreviousElementNode<'r> {
     dummy: &'r str,
 }
 
@@ -101,6 +101,15 @@ where
             head: Some(new_node),
         }
     }
+
+    pub fn with_additional_fail_matcher(
+        &'r self,
+        fail_matcher: &'r Matcher,
+    ) -> ContextTree<'r, FailMatcherNode> {
+        self.with_additional_node(FailMatcherNode {
+            fail_matcher: ChainBehavior::AndParent(Some(fail_matcher))
+        })
+    }
 }
 
 fn test_context() {