Goal:
  
  A : Type
  P : list A → A → Type
  Q : list A → list A → A → A → Type
  Γ' : list A
  H : All2_fold Q [] Γ'
  ============================
   (let H := CoreTactics.block in
    All2_fold (λ (Γ Γ' : list A) (d d' : A), P Γ d × Q Γ Γ' d d') [] Γ')


DEBUG:Going to execute:
CoreTactics.revert_until H
DEBUG LTAC Evaluated term: (let H := CoreTactics.block in
                            All2_fold
                              (λ (Γ Γ' : list A) (d d' : A),
                                 P Γ d × Q Γ Γ' d d') [] Γ')