Goal:
  
  A : Type
  B : Type
  C : Type
  P : A → B → C → Prop
  b : B
  l' : list B
  f : Forall3 P [] (b :: l') []
  ============================
   False


DEBUG:Going to execute:
inversion_clear H
Level 1: evaluation returns
inversion_clear H
where
H := f
of type
intropattern of type tacvalue