Goal:
  
  A : Type
  B : Type
  C : Type
  P : nat → A → B → Type
  Q : B → C → Type
  R : nat → A → C → Type
  S : nat → A → C → Type
  y0 : C
  l' : list C
  n : nat
  x : A
  y : B
  l : list A
  r : list B
  r0 : P n x y
  a : All2i P (Datatypes.S n) l r
  q : Q y y0
  b : All2 Q r l'
  c : All2i R n (x :: l) (y0 :: l')
  ============================
   (let H := CoreTactics.block in
    (∀ (n : nat) (x : A) (y : B) (z : C), P n x y → Q y z → R n x z → S n x z)
    → (∀ l'' : list C,
         All2 Q r l''
         → All2i R (Datatypes.S n) l l'' → All2i S (Datatypes.S n) l l'')
      → let H0 := CoreTactics.block in All2i S n (x :: l) (y0 :: l'))


DEBUG:Going to execute:
get_signature_pack id id'; hnf in (value of id');
            hnf in (type of id')
Level 3: evaluation returns
get_signature_pack id id'; hnf in (value of id'); hnf in (type of id');
 lazymatch goal with
 | id':=?v:_
   |- context [ id ] =>
       generalize (eq_refl : v = id'); clearbody id'; simpl in id';
        cont id id' id v
 | id':=?v:_
   |- _ =>
       let id'1 := fresh id' in
       let id'2 := fresh id' in
       set (id'2 := pr2 id'); set (id'1 := pr1 id') in id'2;
        hnf in (value of id'1), (value of id'2); try red in (type of id'2);
        match goal with
        | id'1:=?t:_
          |- _ =>
              generalize (eq_refl : t = id'1); clearbody id'2 id'1; clear id'
               id; try unfold signature in id'2; hnf in id'2; 
               simpl in id'2; rename id'2 into id; 
               cont id id id'1 t
        end
 end
where
id' := c0
of type
intropattern
id := c
of type
constr
cont := fun id id' id'1 t => try rename id into id',id' into id; cont id'1 id
        where
        id := c
        of type
        constr
        cont := fun id id' => DepElim.decompose_exists id id'
                where
                id := c
                of type
                constr
        of type
        tacvalue
of type
tacvalue of type tacvalue

Level 2: evaluation returns
get_signature_pack id id'; hnf in (value of id'); hnf in (type of id');
 lazymatch goal with
 | id':=?v:_
   |- context [ id ] =>
       generalize (eq_refl : v = id'); clearbody id'; simpl in id';
        cont id id' id v
 | id':=?v:_
   |- _ =>
       let id'1 := fresh id' in
       let id'2 := fresh id' in
       set (id'2 := pr2 id'); set (id'1 := pr1 id') in id'2;
        hnf in (value of id'1), (value of id'2); try red in (type of id'2);
        match goal with
        | id'1:=?t:_
          |- _ =>
              generalize (eq_refl : t = id'1); clearbody id'2 id'1; clear id'
               id; try unfold signature in id'2; hnf in id'2; 
               simpl in id'2; rename id'2 into id; 
               cont id id id'1 t
        end
 end
where
id' := c0
of type
intropattern
id := c
of type
constr
cont := fun id id' id'1 t => try rename id into id',id' into id; cont id'1 id
        where
        id := c
        of type
        constr
        cont := fun id id' => DepElim.decompose_exists id id'
                where
                id := c
                of type
                constr
        of type
        tacvalue
of type
tacvalue of type tacvalue

Level 1: evaluation returns
get_signature_pack id id'; hnf in (value of id'); hnf in (type of id');
 lazymatch goal with
 | id':=?v:_
   |- context [ id ] =>
       generalize (eq_refl : v = id'); clearbody id'; simpl in id';
        cont id id' id v
 | id':=?v:_
   |- _ =>
       let id'1 := fresh id' in
       let id'2 := fresh id' in
       set (id'2 := pr2 id'); set (id'1 := pr1 id') in id'2;
        hnf in (value of id'1), (value of id'2); try red in (type of id'2);
        match goal with
        | id'1:=?t:_
          |- _ =>
              generalize (eq_refl : t = id'1); clearbody id'2 id'1; clear id'
               id; try unfold signature in id'2; hnf in id'2; 
               simpl in id'2; rename id'2 into id; 
               cont id id id'1 t
        end
 end
where
id' := c0
of type
intropattern
id := c
of type
constr
cont := fun id id' id'1 t => try rename id into id',id' into id; cont id'1 id
        where
        id := c
        of type
        constr
        cont := fun id id' => DepElim.decompose_exists id id'
                where
                id := c
                of type
                constr
        of type
        tacvalue
of type
tacvalue of type tacvalue