Introduce functions to compare children and assert there are no children.

src/compare/util.rs

@@ -1,8 +1,12 @@
 use std::str::FromStr;
 
+use super::diff::DiffEntry;
+use super::diff::DiffStatus;
 use super::elisp_fact::GetElispFact;
 use super::sexp::Token;
+use crate::compare::diff::compare_ast_node;
 use crate::compare::sexp::unquote;
+use crate::types::AstNode;
 use crate::types::GetStandardProperties;
 use crate::types::StandardProperties;
 
@@ -252,3 +256,47 @@ where
         .map_or(Ok(None), |r| r.map(Some))?;
     Ok(parsed_number)
 }
+
+pub(crate) fn compare_children<'b, 's, 'x, RC>(
+    source: &'s str,
+    emacs: &'b Token<'s>,
+    rust_children: &'x Vec<RC>,
+    child_status: &mut Vec<DiffEntry<'b, 's>>,
+    this_status: &mut DiffStatus,
+    message: &mut Option<String>,
+) -> Result<(), Box<dyn std::error::Error>>
+where
+    AstNode<'b, 's>: From<&'x RC>,
+{
+    let emacs_children = emacs.as_list()?;
+    let emacs_children_length = emacs_children.len() - 2;
+    if emacs_children_length != rust_children.len() {
+        *this_status = DiffStatus::Bad;
+        *message = Some(format!(
+            "Child length mismatch (emacs != rust) {:?} != {:?}",
+            emacs_children_length,
+            rust_children.len()
+        ));
+    }
+    for (emacs_child, rust_child) in emacs_children.iter().skip(2).zip(rust_children.iter()) {
+        child_status.push(compare_ast_node(source, emacs_child, rust_child.into())?);
+    }
+    Ok(())
+}
+
+pub(crate) fn assert_no_children<'b, 's>(
+    emacs: &'b Token<'s>,
+    this_status: &mut DiffStatus,
+    message: &mut Option<String>,
+) -> Result<(), Box<dyn std::error::Error>> {
+    let emacs_children_length = emacs.as_list()?.len();
+    // 2, one for the name of the node and one for the properties. Children would come after that.
+    if emacs_children_length != 2 {
+        *this_status = DiffStatus::Bad;
+        *message = Some(format!(
+            "Should have no children but emacs has {:?} children.",
+            emacs_children_length - 2,
+        ));
+    }
+    Ok(())
+}