Goal:
    A : Type  P : list A → A → Type  l : list A  a : All_fold P l
  ============================
   (NoConfusionHom_All_fold A P l a a)


DEBUG:Going to execute:
idtac
DEBUG LTAC Evaluated term: a
DEBUG LTAC Evaluated term: (All_fold P l)
Level 5: type of id
 has value 
(All_fold P l)