proposition: Lemma hcancelPtV A x (v1 v2 : A) : valid (x :-> v1) -> x :-> v1 = x :-> v2 -> v1 = v2.
proof: Proof. by move=>V; move/(cancelPt V)/dyn_inj. Qed.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat eqtype seq path) pcm(options axioms finmap) pcm(pcm unionmap)