{A A' B B' : Type} (h : A + B -> A' + B') (Hb : forall b:B, is_inr (h (inr b))) : B -> B' := fun b => un_inr (h (inr b)) (Hb b).
Require Import HoTT.Basics. Require Import Types.Empty Types.Unit Types.Prod Types.Sigma. Require Import Types.Bool.