Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  Q : list A → list A → A → A → Type
  h1 : sigma (λ _ : list A, list A)
  h : All2_fold Q (pr1 h1) (pr2 h1)
  ============================
   ({| pr1 := []; pr2 := [] |} = h1
    → let H := CoreTactics.block in
      let H0 := CoreTactics.block in
      All2_fold (λ (Γ Δ : list A) (x y : A), P Γ Δ x y × Q Γ Δ x y) [] [])


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 := {| pr1 := []; pr2 := [] |}
of type
constr
id'1 := h1
of type
constr
id' := h
of type
ident
id := h
of type
ident
cont := fun id id' => DepElim.decompose_exists id id'
        where
        id := h
        of type
        ident
of type
tacvalue of type tacvalue