Hint Resolve bot_unit.

(* Specifications: *)
Lemma join_bot: join emptyshare emptyshare emptyshare.
Lemma share_rel_nonidentity:
forall {sh1 sh2}, nonidentity sh1 -> nonidentity sh2 -> nonidentity (Share.rel sh1 sh2).
Lemma share_rel_nonunit: forall {sh1 sh2: Share.t},
nonunit sh1 -> nonunit sh2 -> nonunit (Share.rel sh1 sh2).
Lemma decompose_bijection: forall sh1 sh2,
sh1 = sh2 <-> decompose sh1 = decompose sh2.