+ | (C.Prod _, t2) ->
+ let t2' = R.whd ~subst context t2 in
+ (match t2' with
+ C.Prod _ ->
+ fo_unif_subst test_equality_only
+ subst context metasenv t1 t2' ugraph
+ | _ -> raise (UnificationFailure "8"))
+ | (t1, C.Prod _) ->
+ let t1' = R.whd ~subst context t1 in
+ (match t1' with
+ C.Prod _ ->
+ fo_unif_subst test_equality_only
+ subst context metasenv t1' t2 ugraph
+ | _ -> raise (UnificationFailure "9"))