⊦ validrefnotnull(str, r, ty, st) ↔ r ≠ jvmref ∧ validref(str, r, ty, st)
⊦ newref(r, st) → ¬ validref(str, r, ty, st)
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (st, ty, r, str)]]