lang: ast: fix incorrect return types; add function to determine expression tokens

lang/ast/expr.c

@@ -0,0 +1,28 @@
+#include "ctx.h"
+#include "node.h"
+
+#include <blue/object/string.h>
+#include <ivy/lang/lex.h>
+
+struct expr_parser_state {
+	struct parser_state s_base;
+};
+
+static enum ivy_status add_child(
+	struct ivy_ast_node *parent, struct ivy_ast_node *child)
+{
+	struct ivy_ast_expr_node *c = (struct ivy_ast_expr_node *)parent;
+
+	if (!c->n_child) {
+		c->n_child = child;
+		return IVY_OK;
+	}
+
+	return IVY_ERR_NOT_SUPPORTED;
+}
+
+struct ast_node_type expr_node_ops = {
+	.n_add_child = add_child,
+	.n_state_size = sizeof(struct expr_parser_state),
+	.n_node_size = sizeof(struct ivy_ast_expr_node),
+};