Goal:
  
  A : Type
  P : nat → A → Type
  n : nat
  x : A
  Γ : list A
  IHΓ : All_fold (λ (Γ : list A) (d : A), P (n + #|Γ|) d) (List.rev Γ)
        → Alli P n Γ
  a1 : list A
  a : All_fold (λ (Γ : list A) (d : A), P (n + #|Γ|) d) a1
  ============================
   (x :: List.rev Γ = a1
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in Alli P n (Γ ++ [x]))


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 := x :: List.rev Γ
of type
constr
id'1 := a1
of type
constr
id' := a
of type
ident
id := a
of type
ident
cont := fun id id' => DepElim.decompose_exists id id'
        where
        id := a
        of type
        ident
of type
tacvalue of type tacvalue