Update ci->mid according to surrounding scope; fix
MODIFY
src/vm.c
src/vm.c
@@ -569,6 +569,7 @@ eval_under(mrb_state *mrb, mrb_value self, mrb_value blk, struct RClass *c)
p = mrb_proc_ptr(blk);
ci->proc = p;
ci->argc = 1;
+ ci->mid = ci[-1].mid;
if (MRB_PROC_CFUNC_P(p)) {
stack_extend(mrb, 3, 0);
mrb->c->stack[0] = self;

Update ci->mid according to surrounding scope; fix #3490