lang: codegen: redesign again to use purely pre-order ast traversal

lang/ast/node.c

@@ -212,6 +212,11 @@ token_parse_function get_token_parser(
 	return NULL;
 }
 
+struct ivy_ast_node *ivy_ast_node_create(enum ivy_ast_node_type type)
+{
+	return ast_node_create(type);
+}
+
 struct ivy_ast_node *ast_node_create(enum ivy_ast_node_type type)
 {
 	const struct ast_node_type *type_info = get_ast_node_type(type);
@@ -296,3 +301,18 @@ const char *ivy_ast_node_type_to_string(enum ivy_ast_node_type v)
 		return "";
 	}
 }
+
+void ivy_ast_unit_add_node(struct ivy_ast_unit_node *unit, struct ivy_ast_node *child)
+{
+	b_queue_push_back(&unit->n_children, &child->n_entry);
+}
+
+struct ivy_ast_node *ivy_ast_unit_dequeue_node(struct ivy_ast_unit_node *unit)
+{
+	b_queue_entry *entry = b_queue_pop_front(&unit->n_children);
+	if (!entry) {
+		return NULL;
+	}
+
+	return b_unbox(struct ivy_ast_node, entry, n_entry);
+}