(************************************************************************)
(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
(*   \VV/  **************************************************************)
(*    //   *      This file is distributed under the terms of the       *)
(*         *       GNU Lesser General Public License Version 2.1        *)
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(* This needs unification on type *)

Goal (n,m:nat)(eq nat (S m) (S n)).
Intros.
Apply f_equal.

(* f_equal : (A,B:Set; f:(A->B); x,y:A)x=y->(f x)=(f y) *)
(* and A cannot be deduced from the goal but only from the type of f, x or y *)


(* This needs step by step unfolding *)

Fixpoint T [n:nat] : Prop := Cases n of O => True | (S p) => n=n->(T p) end.
Require Arith.

Goal (T (3))->(T (1)).
Intro H.
Apply H.