Avoid infinite recursion in `method_missing`; ref
MODIFY
src/vm.c
src/vm.c
@@ -1419,7 +1419,7 @@ RETRY_TRY_BLOCK:
if (MRB_METHOD_UNDEF_P(m)) {
mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
m = mrb_method_search_vm(mrb, &c, missing);
- if (MRB_METHOD_UNDEF_P(m)) {
+ if (MRB_METHOD_UNDEF_P(m) || (missing == mrb->c->ci->mid && mrb_obj_eq(mrb, regs[0], recv))) {
mrb_value args = (argc < 0) ? regs[a+1] : mrb_ary_new_from_values(mrb, n, regs+a+1);
ERR_PC_SET(mrb, pc);
mrb_method_missing(mrb, mid, recv, args);

Avoid infinite recursion in `method_missing`; ref #3908