rk = r0 -- sk ⊦ r = r0, okbytearray(r, st[rk, val]) ↔ okbytearray(r, st)
[[CONCRETESIMPRULES : ([CSIMPELIM : ⊦ r = rk .ref ∧ sk = rk .key ↔ rk = r -- sk])], [EXTRATERMS : (rk, r0, sk)]]