Goal:
  
  A : Type
  B : Type
  P : A → B → Prop
  t : B
  l' : list B
  e : Some t = Some t
  x : A
  l : list A
  H : P x t
  h : Forall2 P l l'
  ============================
   (nth_error (x :: l) 0 = Some x ∧ P x t)


DEBUG:Going to execute:
split
DEBUG LTAC Evaluated term: x