Do not need to take `target_class` from the upper proc.
Since it is already set in `mrb_proc_new()`.
MODIFY
src/proc.c
src/proc.c
@@ -69,7 +69,7 @@ closure_setup(mrb_state *mrb, struct RProc *p)
e = ci->env;
}
else {
- struct RClass *tc = MRB_PROC_TARGET_CLASS(up);
+ struct RClass *tc = MRB_PROC_TARGET_CLASS(p);
e = env_new(mrb, up->body.irep->nlocals);
ci->env = e;

Do not need to take `target_class` from the upper proc.

Since it is already set in `mrb_proc_new()`.