Implement the structure to the check_fail_matcher function.

src/parser/list.rs

@@ -25,7 +25,17 @@ impl<T> List<T> {
         }
     }
 
+    pub fn without_front(&self) -> List<T> {
+        List {
+            head: self.head.as_ref().map(|node| node.parent.clone()).flatten()
+        }
+    }
+
     pub fn get_data(&self) -> Option<&T> {
         self.head.as_ref().map(|rc_node| &rc_node.data)
     }
+
+    pub fn is_empty(&self) -> bool {
+        self.head.is_none()
+    }
 }

src/parser/new_context.rs

@@ -1,3 +1,5 @@
+use nom::bytes::complete::take;
+use nom::combinator::not;
 use nom::error::VerboseError;
 use nom::IResult;
 
@@ -21,8 +23,27 @@ impl<'r> ContextTree<'r> {
     }
 
     pub fn check_fail_matcher<'s>(&'r self, i: &'s str) -> IResult<&'s str, &'s str, VerboseError<&'s str>> {
-        // todo
-        todo!()
+        let mut current_node = &self.tree;
+        while !current_node.is_empty() {
+            let context_element = current_node.get_data().expect("While looop proves its Some()");
+            match context_element {
+                ContextElement::FailMatcherNode(fail_matcher) => {
+                    match fail_matcher.fail_matcher {
+                        ChainBehavior::AndParent(Some(matcher)) => todo!(),
+                        ChainBehavior::AndParent(None) => todo!(),
+                        ChainBehavior::IgnoreParent(_) => todo!(),
+                        ChainBehavior::IgnoreParent(None) => todo!(),
+                    };
+                },
+                ContextElement::PreviousElementNode(_) => todo!(),
+            };
+
+            current_node = &current_node.without_front();
+        }
+
+        // TODO: Make this a custom error
+        not(take(0usize))(i)?;
+        unreachable!()
     }
 }