proposition: Lemma hcancelV A x (v1 v2 : A) h1 h2 : valid (x :-> v1 \+ h1) -> x :-> v1 \+ h1 = x :-> v2 \+ h2 -> [/\ v1 = v2, valid h1 & h1 = h2].
proof: Proof. by move=>V; case/(cancel V); move/dyn_inj. Qed.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat eqtype seq path) pcm(options axioms finmap) pcm(pcm unionmap)