Ltac is_ground_goal :=
  match goal with
    |- ?T => is_ground T
  end.(** We will use the [block] definition to separate the goal from the
   equalities generated by the tactic. *)

Definition block {A : Type} (a : A) := a.Ltac block_goal := match goal with [ |- ?T ] => change (block T) end.Ltac unblock_goal := unfold block in *.(** Notation for heterogeneous equality. *)
#[deprecated(since="8.17")]
Notation " x ~= y " := (@JMeq _ x _ y) (at level 70, no associativity).(** Do something on an heterogeneous equality appearing in the context. *)

Ltac on_JMeq tac :=
  match goal with
    | [ H : @JMeq ?x ?X ?y ?Y |- _ ] => tac H
  end.(** Try to apply [JMeq_eq] to get back a regular equality when the two types are equal. *)

Ltac simpl_one_JMeq :=
  on_JMeq ltac:(fun H => apply JMeq_eq in H).(** Repeat it for every possible hypothesis. *)

Ltac simpl_JMeq := repeat simpl_one_JMeq.(** Just simplify an h.eq. without clearing it. *)

Ltac simpl_one_dep_JMeq :=
  on_JMeq
  ltac:(fun H => let H' := fresh "H" in
    assert (H' := JMeq_eq H)).(** Simplify dependent equality using sigmas to equality of the second projections if possible.
   Uses UIP. *)

Ltac simpl_existT :=
  match goal with
    [ H : existT _ ?x _ = existT _ ?x _ |- _ ] =>
    let Hi := fresh H in assert(Hi:=inj_pairT2 _ _ _ _ _ H) ; clear H
  end.Ltac simpl_existTs := repeat simpl_existT.(** Tries to eliminate a call to [eq_rect] (the substitution principle) by any means available. *)

Ltac elim_eq_rect :=
  match goal with
    | [ |- ?t ] =>
      match t with
        | context [ @eq_rect _ _ _ _ _ ?p ] =>
          let P := fresh "P" in
            set (P := p); simpl in P ;
              ((case P ; clear P) || (clearbody P; rewrite (UIP_refl _ _ P); clear P))
        | context [ @eq_rect _ _ _ _ _ ?p _ ] =>
          let P := fresh "P" in
            set (P := p); simpl in P ;
              ((case P ; clear P) || (clearbody P; rewrite (UIP_refl _ _ P); clear P))
      end
  end.(** Rewrite using uniqueness of identity proofs [H = eq_refl]. *)

Ltac simpl_uip :=
  match goal with
    [ H : ?X = ?X |- _ ] => rewrite (UIP_refl _ _ H) in *; clear H
  end.(** Simplify equalities appearing in the context and goal. *)

Ltac simpl_eq := simpl ; unfold eq_rec_r, eq_rec ; repeat (elim_eq_rect ; simpl) ; repeat (simpl_uip ; simpl).(** Try to abstract a proof of equality, if no proof of the same equality is present in the context. *)

Ltac abstract_eq_hyp H' p :=
  let ty := type of p in
  let tyred := eval simpl in ty in
    match tyred with
      ?X = ?Y =>
      match goal with
        | [ H : X = Y |- _ ] => fail 1
        | _ => set (H':=p) ; try (change p with H') ; clearbody H' ; simpl in H'
      end
    end.(** Apply the tactic tac to proofs of equality appearing as coercion arguments.
   Just redefine this tactic (using [Ltac on_coerce_proof tac ::=]) to handle custom coercion operators.
   *)

Ltac on_coerce_proof tac T :=
  match T with
    | context [ eq_rect _ _ _ _ ?p ] => tac p
  end.Ltac on_coerce_proof_gl tac :=
  match goal with
    [ |- ?T ] => on_coerce_proof tac T
  end.(** Abstract proofs of equalities of coercions. *)

Ltac abstract_eq_proof := on_coerce_proof_gl ltac:(fun p => let H := fresh "eqH" in abstract_eq_hyp H p).Ltac abstract_eq_proofs := repeat abstract_eq_proof.(** Factorize proofs, by using proof irrelevance so that two proofs of the same equality
   in the goal become convertible. *)

Ltac pi_eq_proof_hyp p :=
  let ty := type of p in
  let tyred := eval simpl in ty in
  match tyred with
    ?X = ?Y =>
    match goal with
      | [ H : X = Y |- _ ] =>
        match p with
          | H => fail 2
          | _ => rewrite (UIP _ X Y p H)
        end
      | _ => fail " No hypothesis with same type "
    end
  end.(** Factorize proofs of equality appearing as coercion arguments. *)

Ltac pi_eq_proof := on_coerce_proof_gl pi_eq_proof_hyp.Ltac pi_eq_proofs := repeat pi_eq_proof.(** The two preceding tactics in sequence. *)

Ltac clear_eq_proofs :=
  abstract_eq_proofs ; pi_eq_proofs.

Lemma JMeq_eq_refl {A} (x : A) : JMeq_eq (@JMeq_refl _ x) = eq_refl.