Implement empty iterator for types with no ast node children.

src/iter/ast_node_iter.rs

@@ -1,7 +1,13 @@
+use std::marker::PhantomData;
+
 use super::ast_node::AstNode;
+use super::macros::simple_iter;
 use crate::types::Bold;
+use crate::types::Code;
 use crate::types::Italic;
 use crate::types::Object;
+use crate::types::StrikeThrough;
+use crate::types::Underline;
 
 pub enum AstNodeIter<'r, 's> {
     // Document Nodes
@@ -34,9 +40,9 @@ pub enum AstNodeIter<'r, 's> {
     // Objects
     Bold(BoldIter<'r, 's>),
     Italic(ItalicIter<'r, 's>),
-    // Underline(UnderlineIter<'r, 's>),
-    // StrikeThrough(StrikeThroughIter<'r, 's>),
-    // Code(CodeIter<'r, 's>),
+    Underline(UnderlineIter<'r, 's>),
+    StrikeThrough(StrikeThroughIter<'r, 's>),
+    Code(CodeIter<'r, 's>),
     // Verbatim(VerbatimIter<'r, 's>),
     // PlainText(PlainTextIter<'r, 's>),
     // RegularLink(RegularLinkIter<'r, 's>),
@@ -85,32 +91,38 @@ impl<'r, 's> IntoIterator for &'r Bold<'s> {
     }
 }
 
-macro_rules! simple_iter {
-    ($astnodetype:ty, $itertype:ident, $innertype:ty) => {
-        pub struct $itertype<'r, 's> {
-            next: $innertype,
-        }
+simple_iter!(Italic<'s>, ItalicIter, std::slice::Iter<'r, Object<'s>>);
+simple_iter!(
+    Underline<'s>,
+    UnderlineIter,
+    std::slice::Iter<'r, Object<'s>>
+);
+simple_iter!(
+    StrikeThrough<'s>,
+    StrikeThroughIter,
+    std::slice::Iter<'r, Object<'s>>
+);
 
-        impl<'r, 's> Iterator for $itertype<'r, 's> {
-            type Item = AstNode<'r, 's>;
-
-            fn next(&mut self) -> Option<Self::Item> {
-                self.next.next().map(Into::<AstNode>::into)
-            }
-        }
-
-        impl<'r, 's> IntoIterator for &'r $astnodetype {
-            type Item = AstNode<'r, 's>;
-
-            type IntoIter = $itertype<'r, 's>;
-
-            fn into_iter(self) -> Self::IntoIter {
-                $itertype {
-                    next: self.children.iter(),
-                }
-            }
-        }
-    };
+pub struct CodeIter<'r, 's> {
+    phantom: PhantomData<&'r Code<'s>>,
 }
 
-simple_iter!(Italic<'s>, ItalicIter, std::slice::Iter<'r, Object<'s>>);
+impl<'r, 's> Iterator for CodeIter<'r, 's> {
+    type Item = AstNode<'r, 's>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        None
+    }
+}
+
+impl<'r, 's> IntoIterator for &'r Code<'s> {
+    type Item = AstNode<'r, 's>;
+
+    type IntoIter = CodeIter<'r, 's>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        CodeIter {
+            phantom: PhantomData,
+        }
+    }
+}

src/iter/macros.rs

@@ -0,0 +1,30 @@
+/// Create iterators for ast nodes where it only has to iterate over children
+macro_rules! simple_iter {
+    ($astnodetype:ty, $itertype:ident, $innertype:ty) => {
+        pub struct $itertype<'r, 's> {
+            next: $innertype,
+        }
+
+        impl<'r, 's> Iterator for $itertype<'r, 's> {
+            type Item = AstNode<'r, 's>;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                self.next.next().map(Into::<AstNode>::into)
+            }
+        }
+
+        impl<'r, 's> IntoIterator for &'r $astnodetype {
+            type Item = AstNode<'r, 's>;
+
+            type IntoIter = $itertype<'r, 's>;
+
+            fn into_iter(self) -> Self::IntoIter {
+                $itertype {
+                    next: self.children.iter(),
+                }
+            }
+        }
+    };
+}
+
+pub(crate) use simple_iter;

src/iter/mod.rs

@@ -1,2 +1,3 @@
 mod ast_node;
 mod ast_node_iter;
+mod macros;