Goal:
    A : Type  P : list A → A → Type
  ============================
   (let H := CoreTactics.block in
    NoConfusionHom_All_fold A P [] (All_fold_nil P) (All_fold_nil P)
    → let H0 := CoreTactics.block in All_fold_nil P = All_fold_nil P)


DEBUG:Going to execute:
change T; CoreTactics.intros_until_block
Level 5: T
 has value 
(NoConfusionHom_All_fold A P [] (All_fold_nil P) (All_fold_nil P)
 → let H := CoreTactics.block in All_fold_nil P = All_fold_nil P)