Goal:
    x : V.t  n : Z  y : V.t  H0 : V.eq x x  H : n = n  H2 : V.lt y y
  ============================
   False


DEBUG:Going to execute:
PTRDEBUGTACmatch goal with
           | |- ?X1 -> ?X2 => intro
           | |- ~ _ => unfold not at 1; intro
           end