Implement a wrapper type for AST nodes.

This is to make it impossible to have a collision for attribute names that are real attributes vs attributes I've added for structure (like children and ast_node).

src/wasm_test/compare.rs

@@ -87,7 +87,7 @@ fn compare_json_value<'b, 's>(
     emacs: &'b Token<'s>,
 ) -> Result<WasmDiffResult<'s>, Box<dyn std::error::Error>> {
     match (value, emacs) {
-        (serde_json::Value::Object(wasm), Token::List(el)) if wasm.contains_key("__ast_node") => {
+        (serde_json::Value::Object(wasm), Token::List(el)) if wasm.contains_key("ast_node") => {
             // We hit a regular ast node.
             compare_ast_node(source, el, wasm)
         }
@@ -133,7 +133,7 @@ fn compare_ast_node<'b, 's, 'p>(
             .ok_or("Should have a name as the first child.")?
             .as_atom()?;
         let wasm_name = wasm
-            .get("__ast_node")
+            .get("ast_node")
             .ok_or("Should have a ast node type.")?
             .as_str()
             .ok_or("Ast node type should be a string.")?;