Goal:
  
  A : Type
  B : Type
  C : Type
  A' : Type
  B' : Type
  C' : Type
  R : A' → B' → C' → Prop
  f : A → A'
  g : B → B'
  h : C → C'
  c : C
  l'' : list C
  ============================
   (Forall3 R (map f []) (map g []) (map h (c :: l''))
    → Forall3 (λ (x : A) (y : B) (z : C), R (f x) (g y) (h z)) [] []
        (c :: l''))


DEBUG:Going to execute:
solve [ inversion 1 ]
Level 0: Backtrace:

Proof is not complete.
Level 0: Backtrace:

No applicable tactic.