Goal:
  
  A : Type
  P : A → Prop
  Q : A → Prop
  a : A
  l : list A
  a0 : A
  l' : list A
  IHl : All P l → All Q l' → #|l| = #|l'| → All2 (λ x y : A, P x ∧ Q y) l l'
  p : P a
  ha : All P l
  hb1 : list A
  hb : All Q hb1
  ============================
   (a0 :: l' = hb1
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in
      S #|l| = S #|l'| → All2 (λ x y : A, P x ∧ Q y) (a :: l) (a0 :: l'))


DEBUG:Going to execute:
try rename id into id',id' into id
Level 3: evaluation returns
try rename id into id',id' into id; cont id'1 id
where
t := a0 :: l'
of type
constr
id'1 := hb1
of type
constr
id' := hb
of type
constr
id := hb
of type
constr
cont := fun id id' => DepElim.decompose_exists id id'
        where
        id := hb
        of type
        constr
of type
tacvalue of type tacvalue