lang: ast: replace ast node print callback with to_string

lang/ast/string.c

@@ -1,6 +1,13 @@
 #include "ctx.h"
 #include "expr/expr.h"
 #include "node.h"
+#include <blue/object/string.h>
+
+static void to_string(struct ivy_ast_node *node, b_string *str)
+{
+	struct ivy_ast_string_node *s = (struct ivy_ast_string_node *)node;
+	b_string_append_cstrf(str, "%s (\"%s\")", ivy_ast_node_type_to_string(node->n_type), s->n_value->t_str);
+}
 
 struct token_parse_result parse_string(
 	struct ivy_parser *ctx, struct ivy_token *tok)
@@ -63,6 +70,7 @@ static void collect_children(
 }
 
 struct ast_node_type string_node_ops = {
+	.n_to_string = to_string,
 	.n_state_size = sizeof(struct parser_state),
 	.n_node_size = sizeof(struct ivy_ast_string_node),
 };