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:
CoreTactics.destruct_sigma id
Level 4: evaluation returns
CoreTactics.destruct_sigma id; destruct id
where
id := a
of type
constr of type tacvalue