proposition: Lemma lookup_union_Some_raw {A} (m1 m2 : M A) i x : (m1 ∪ m2) !! i = Some x ↔ m1 !! i = Some x ∨ (m1 !! i = None ∧ m2 !! i = Some x).
proof: Proof. rewrite lookup_union. destruct (m1 !! i), (m2 !! i); naive_solver. Qed.
imports: Coq(Permutation) stdpp(options)