Goal:
  
  B : Type
  C : Type
  A : B → Type
  D : C → Type
  l : list B
  l' : list C
  a : All A l
  all : All2 (λ (x : B) (y : C), A x → D y) l l'
  ============================
   (All ?P l)


DEBUG:Going to execute:
eassumption
Level 1: Backtrace:

No applicable tactic.
Level 0: Backtrace:

No applicable tactic.