proposition: Lemma domPtUnX A (v : A) x i : valid (x :-> v \+ i) -> x \in dom (x :-> v \+ i).
proof: Proof. by move=>D; rewrite domPtUn inE /= D eq_refl. Qed.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat eqtype seq path) pcm(options axioms finmap) pcm(pcm unionmap)