tactics.v 89.7 KB
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From iris.proofmode Require Import coq_tactics.
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From iris.proofmode Require Import base intro_patterns spec_patterns sel_patterns.
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From iris.bi Require Export bi big_op.
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From stdpp Require Import namespaces.
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From iris.proofmode Require Export classes notation.
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From iris.proofmode Require Import class_instances.
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From stdpp Require Import hlist pretty.
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Set Default Proof Using "Type".
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Export ident.
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Declare Reduction env_cbv := cbv [
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  option_bind
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  beq ascii_beq string_beq positive_beq Pos.succ ident_beq
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  env_lookup env_lookup_delete env_delete env_app env_replace env_dom
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  env_intuitionistic env_spatial env_counter env_spatial_is_nil envs_dom
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  envs_lookup envs_lookup_delete envs_delete envs_snoc envs_app
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    envs_simple_replace envs_replace envs_split
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    envs_clear_spatial envs_clear_persistent envs_incr_counter
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    envs_split_go envs_split prop_of_env].
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Ltac env_cbv :=
  match goal with |- ?u => let v := eval env_cbv in u in change v end.
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Ltac env_reflexivity := env_cbv; exact eq_refl.
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(** For most of the tactics, we want to have tight control over the order and
way in which type class inference is performed. To that end, many tactics make
use of [notypeclasses refine] and the [iSolveTC] tactic to manually invoke type
class inference.

The tactic [iSolveTC] does not use [apply _], as that often leads to issues
because it will try to solve all evars whose type is a typeclass, in
dependency order (according to Matthieu). If one fails, it aborts. However, we
generally rely on progress on the main goal to be solved to make progress
elsewhere. With [typeclasses eauto], that seems to work better.

A drawback of [typeclasses eauto] is that it is multi-success, i.e. whenever
subsequent tactics fail, it will backtrack to [typeclasses eauto] to try the
next type class instance. This is almost always undesired and leads to poor
performance and horrible error messages, so we wrap it in a [once]. *)
Ltac iSolveTC :=
  solve [once (typeclasses eauto)].

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(** * Misc *)
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Ltac iMissingHyps Hs :=
  let Δ :=
    lazymatch goal with
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    | |- envs_entails ?Δ _ => Δ
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    | |- context[ envs_split _ _ ?Δ ] => Δ
    end in
  let Hhyps := eval env_cbv in (envs_dom Δ) in
  eval vm_compute in (list_difference Hs Hhyps).

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Ltac iTypeOf H :=
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  let Δ := match goal with |- envs_entails ?Δ _ => Δ end in
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  eval env_cbv in (envs_lookup H Δ).
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Tactic Notation "iMatchHyp" tactic1(tac) :=
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  match goal with
  | |- context[ environments.Esnoc _ ?x ?P ] => tac x P
  end.

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(** * Start a proof *)
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Tactic Notation "iStartProof" :=
  lazymatch goal with
  | |- envs_entails _ _ => idtac
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  | |- ?φ => notypeclasses refine (as_emp_valid_2 φ _ _);
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               [apply _ || fail "iStartProof: not a Bi entailment"
               |apply tac_adequate]
  end.

(* Same as above, with 2 differences :
   - We can specify a BI in which we want the proof to be done
   - If the goal starts with a let or a ∀, they are automatically
     introduced. *)
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Tactic Notation "iStartProof" uconstr(PROP) :=
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  lazymatch goal with
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  | |- @envs_entails ?PROP' _ _ =>
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    (* This cannot be shared with the other [iStartProof], because
    type_term has a non-negligeable performance impact. *)
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    let x := type_term (eq_refl : @eq Type PROP PROP') in idtac
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  (* We eta-expand [as_emp_valid_2], in order to make sure that
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     [iStartProof PROP] works even if [PROP] is the carrier type. In
     this case, typing this expression will end up unifying PROP with
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     [bi_car _], and hence trigger the canonical structures mechanism
     to find the corresponding bi. *)
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  | |- ?φ => notypeclasses refine ((λ P : PROP, @as_emp_valid_2 φ _ P) _ _ _);
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               [apply _ || fail "iStartProof: not a Bi entailment"
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               |apply tac_adequate]
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  end.

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(** * Generate a fresh identifier *)
(* Tactic Notation tactics cannot return terms *)
Ltac iFresh :=
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  (* We need to increment the environment counter using [tac_fresh].
     But because [iFresh] returns a value, we have to let bind
     [tac_fresh] wrapped under a match to force evaluation of this
     side-effect. See https://stackoverflow.com/a/46178884 *)
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  let do_incr :=
      lazymatch goal with
      | _ => iStartProof; eapply tac_fresh; first by (env_reflexivity)
      end in
  lazymatch goal with
  |- envs_entails ?Δ _ =>
    let n := eval env_cbv in (env_counter Δ) in
    constr:(IAnon n)
  end.
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(** * Simplification *)
Tactic Notation "iEval" tactic(t) :=
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  iStartProof;
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  eapply tac_eval;
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    [let x := fresh in intros x; t; unfold x; reflexivity
    |].
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Tactic Notation "iEval" tactic(t) "in" constr(H) :=
  iStartProof;
  eapply tac_eval_in with _ H _ _ _;
    [env_reflexivity || fail "iEval:" H "not found"
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    |let x := fresh in intros x; t; unfold x; reflexivity
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    |env_reflexivity
    |].
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Tactic Notation "iSimpl" := iEval simpl.
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Tactic Notation "iSimpl" "in" constr(H) := iEval simpl in H.
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(* It would be nice to also have an `iSsrRewrite`, however, for this we need to
pass arguments to Ssreflect's `rewrite` like `/= foo /bar` in Ltac, see:

  https://sympa.inria.fr/sympa/arc/coq-club/2018-01/msg00000.html

PMP told me (= Robbert) in person that this is not possible today, but may be
possible in Ltac2. *)
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(** * Context manipulation *)
Tactic Notation "iRename" constr(H1) "into" constr(H2) :=
  eapply tac_rename with _ H1 H2 _ _; (* (i:=H1) (j:=H2) *)
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    [env_reflexivity || fail "iRename:" H1 "not found"
    |env_reflexivity || fail "iRename:" H2 "not fresh"|].
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Local Inductive esel_pat :=
  | ESelPure
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  | ESelIdent : bool  ident  esel_pat.
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Ltac iElaborateSelPat pat :=
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  let rec go pat Δ Hs :=
    lazymatch pat with
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    | [] => eval cbv in Hs
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    | SelPure :: ?pat => go pat Δ (ESelPure :: Hs)
    | SelPersistent :: ?pat =>
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       let Hs' := eval env_cbv in (env_dom (env_intuitionistic Δ)) in
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       let Δ' := eval env_cbv in (envs_clear_persistent Δ) in
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       go pat Δ' ((ESelIdent true <$> Hs') ++ Hs)
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    | SelSpatial :: ?pat =>
       let Hs' := eval env_cbv in (env_dom (env_spatial Δ)) in
       let Δ' := eval env_cbv in (envs_clear_spatial Δ) in
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       go pat Δ' ((ESelIdent false <$> Hs') ++ Hs)
    | SelIdent ?H :: ?pat =>
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       lazymatch eval env_cbv in (envs_lookup_delete false H Δ) with
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       | Some (?p,_,?Δ') => go pat Δ' (ESelIdent p H :: Hs)
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       | None => fail "iElaborateSelPat:" H "not found"
       end
    end in
  lazymatch goal with
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  | |- envs_entails ?Δ _ =>
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    let pat := sel_pat.parse pat in go pat Δ (@nil esel_pat)
  end.

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Local Ltac iClearHyp H :=
  eapply tac_clear with _ H _ _; (* (i:=H) *)
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    [env_reflexivity || fail "iClear:" H "not found"
    |env_cbv; apply _ ||
     let P := match goal with |- TCOr (Affine ?P) _ => P end in
     fail "iClear:" H ":" P "not affine and the goal not absorbing"
    |].
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Tactic Notation "iClear" constr(Hs) :=
  let rec go Hs :=
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    lazymatch Hs with
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    | [] => idtac
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    | ESelPure :: ?Hs => clear; go Hs
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    | ESelIdent _ ?H :: ?Hs => iClearHyp H; go Hs
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    end in
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  let Hs := iElaborateSelPat Hs in iStartProof; go Hs.
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Tactic Notation "iClear" "(" ident_list(xs) ")" constr(Hs) :=
  iClear Hs; clear xs.
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(** * Assumptions *)
Tactic Notation "iExact" constr(H) :=
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  eapply tac_assumption with _ H _ _; (* (i:=H) *)
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    [env_reflexivity || fail "iExact:" H "not found"
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    |apply _ ||
     let P := match goal with |- FromAssumption _ ?P _ => P end in
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     fail "iExact:" H ":" P "does not match goal"
    |env_cbv; apply _ ||
     fail "iExact:" H "not absorbing and the remaining hypotheses not affine"].
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Tactic Notation "iAssumptionCore" :=
  let rec find Γ i P :=
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    lazymatch Γ with
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    | Esnoc ?Γ ?j ?Q => first [unify P Q; unify i j|find Γ i P]
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    end in
  match goal with
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  | |- envs_lookup ?i (Envs ?Γp ?Γs _) = Some (_, ?P) =>
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     first [is_evar i; fail 1 | env_reflexivity]
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  | |- envs_lookup ?i (Envs ?Γp ?Γs _) = Some (_, ?P) =>
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     is_evar i; first [find Γp i P | find Γs i P]; env_reflexivity
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  | |- envs_lookup_delete _ ?i (Envs ?Γp ?Γs _) = Some (_, ?P, _) =>
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     first [is_evar i; fail 1 | env_reflexivity]
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  | |- envs_lookup_delete _ ?i (Envs ?Γp ?Γs _) = Some (_, ?P, _) =>
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     is_evar i; first [find Γp i P | find Γs i P]; env_reflexivity
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  end.
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Tactic Notation "iAssumption" :=
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  let Hass := fresh in
  let rec find p Γ Q :=
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    lazymatch Γ with
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    | Esnoc ?Γ ?j ?P => first
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       [pose proof (_ : FromAssumption p P Q) as Hass;
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        eapply (tac_assumption _ _ j p P);
          [env_reflexivity
          |apply Hass
          |env_cbv; apply _ ||
           fail 1 "iAssumption:" j "not absorbing and the remaining hypotheses not affine"]
       |assert (P = False%I) as Hass by reflexivity;
        apply (tac_false_destruct _ j p P);
          [env_reflexivity
          |exact Hass]
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       |find p Γ Q]
    end in
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  lazymatch goal with
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  | |- envs_entails (Envs ?Γp ?Γs _) ?Q =>
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     first [find true Γp Q | find false Γs Q
           |fail "iAssumption:" Q "not found"]
  end.
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(** * False *)
Tactic Notation "iExFalso" := apply tac_ex_falso.

(** * Making hypotheses persistent or pure *)
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Local Tactic Notation "iPersistent" constr(H) :=
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  eapply tac_persistent with _ H _ _ _; (* (i:=H) *)
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    [env_reflexivity || fail "iPersistent:" H "not found"
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    |apply _ ||
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     let P := match goal with |- IntoPersistent _ ?P _ => P end in
     fail "iPersistent:" P "not persistent"
    |env_cbv; apply _ ||
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     let P := match goal with |- TCOr (Affine ?P) _ => P end in
     fail "iPersistent:" P "not affine and the goal not absorbing"
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    |env_reflexivity|].
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Local Tactic Notation "iPure" constr(H) "as" simple_intropattern(pat) :=
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  eapply tac_pure with _ H _ _ _; (* (i:=H1) *)
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    [env_reflexivity || fail "iPure:" H "not found"
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    |apply _ ||
     let P := match goal with |- IntoPure ?P _ => P end in
     fail "iPure:" P "not pure"
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    |env_cbv; apply _ ||
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     let P := match goal with |- TCOr (Affine ?P) _ => P end in
     fail "iPure:" P "not affine and the goal not absorbing"
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    |intros pat].

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Tactic Notation "iEmpIntro" :=
  iStartProof;
  eapply tac_emp_intro;
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    [env_cbv; apply _ ||
     fail "iEmpIntro: spatial context contains non-affine hypotheses"].
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Tactic Notation "iPureIntro" :=
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  iStartProof;
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  eapply tac_pure_intro;
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    [env_reflexivity
    |apply _ ||
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     let P := match goal with |- FromPure _ ?P _ => P end in
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     fail "iPureIntro:" P "not pure"
    |].
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(** Framing *)
Local Ltac iFrameFinish :=
  lazy iota beta;
  try match goal with
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  | |- envs_entails _ True => by iPureIntro
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  | |- envs_entails _ emp => iEmpIntro
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  end.

Local Ltac iFramePure t :=
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  iStartProof;
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  let φ := type of t in
  eapply (tac_frame_pure _ _ _ _ t);
    [apply _ || fail "iFrame: cannot frame" φ
    |iFrameFinish].

Local Ltac iFrameHyp H :=
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  iStartProof;
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  eapply tac_frame with _ H _ _ _;
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    [env_reflexivity || fail "iFrame:" H "not found"
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    |apply _ ||
     let R := match goal with |- Frame _ ?R _ _ => R end in
     fail "iFrame: cannot frame" R
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    |iFrameFinish].

Local Ltac iFrameAnyPure :=
  repeat match goal with H : _ |- _ => iFramePure H end.

Local Ltac iFrameAnyPersistent :=
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  iStartProof;
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  let rec go Hs :=
    match Hs with [] => idtac | ?H :: ?Hs => repeat iFrameHyp H; go Hs end in
  match goal with
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  | |- envs_entails ?Δ _ =>
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     let Hs := eval cbv in (env_dom (env_intuitionistic Δ)) in go Hs
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  end.

Local Ltac iFrameAnySpatial :=
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  iStartProof;
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  let rec go Hs :=
    match Hs with [] => idtac | ?H :: ?Hs => try iFrameHyp H; go Hs end in
  match goal with
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  | |- envs_entails ?Δ _ =>
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     let Hs := eval cbv in (env_dom (env_spatial Δ)) in go Hs
  end.

Tactic Notation "iFrame" := iFrameAnySpatial.

Tactic Notation "iFrame" "(" constr(t1) ")" :=
  iFramePure t1.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) ")" :=
  iFramePure t1; iFrame ( t2 ).
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) ")" :=
  iFramePure t1; iFrame ( t2 t3 ).
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4) ")" :=
  iFramePure t1; iFrame ( t2 t3 t4 ).
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) ")" :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 ).
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) constr(t6) ")" :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 t6 ).
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) constr(t6) constr(t7) ")" :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 t6 t7 ).
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) constr(t6) constr(t7) constr(t8)")" :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 t6 t7 t8 ).

Tactic Notation "iFrame" constr(Hs) :=
  let rec go Hs :=
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    lazymatch Hs with
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    | [] => idtac
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    | SelPure :: ?Hs => iFrameAnyPure; go Hs
    | SelPersistent :: ?Hs => iFrameAnyPersistent; go Hs
    | SelSpatial :: ?Hs => iFrameAnySpatial; go Hs
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    | SelIdent ?H :: ?Hs => iFrameHyp H; go Hs
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    end
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  in let Hs := sel_pat.parse Hs in go Hs.
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Tactic Notation "iFrame" "(" constr(t1) ")" constr(Hs) :=
  iFramePure t1; iFrame Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) ")" constr(Hs) :=
  iFramePure t1; iFrame ( t2 ) Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) ")" constr(Hs) :=
  iFramePure t1; iFrame ( t2 t3 ) Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4) ")"
    constr(Hs) :=
  iFramePure t1; iFrame ( t2 t3 t4 ) Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) ")" constr(Hs) :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 ) Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) constr(t6) ")" constr(Hs) :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 t6 ) Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) constr(t6) constr(t7) ")" constr(Hs) :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 t6 t7 ) Hs.
Tactic Notation "iFrame" "(" constr(t1) constr(t2) constr(t3) constr(t4)
    constr(t5) constr(t6) constr(t7) constr(t8)")" constr(Hs) :=
  iFramePure t1; iFrame ( t2 t3 t4 t5 t6 t7 t8 ) Hs.

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(** * Basic introduction tactics *)
Local Tactic Notation "iIntro" "(" simple_intropattern(x) ")" :=
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  (* In the case the goal starts with an [let x := _ in _], we do not
     want to unfold x and start the proof mode. Instead, we want to
     use intros. So [iStartProof] has to be called only if [intros]
     fails *)
  intros x ||
    (iStartProof;
     lazymatch goal with
     | |- envs_entails _ _ =>
       eapply tac_forall_intro;
       [apply _ ||
              let P := match goal with |- FromForall ?P _ => P end in
              fail "iIntro: cannot turn" P "into a universal quantifier"
       |lazy beta; intros x]
     end).
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Local Tactic Notation "iIntro" constr(H) :=
  iStartProof;
  first
  [ (* (?Q → _) *)
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    eapply tac_impl_intro with _ H _ _ _; (* (i:=H) *)
      [apply _
      |env_cbv; apply _ ||
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       let P := lazymatch goal with |- Persistent ?P => P end in
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       fail 1 "iIntro: introducing non-persistent" H ":" P
              "into non-empty spatial context"
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      |env_reflexivity || fail 1 "iIntro:" H "not fresh"
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      |apply _
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      |]
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  | (* (_ -∗ _) *)
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    eapply tac_wand_intro with _ H _ _; (* (i:=H) *)
      [apply _
      | env_reflexivity || fail 1 "iIntro:" H "not fresh"
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      |]
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  | fail "iIntro: nothing to introduce" ].
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Local Tactic Notation "iIntro" "#" constr(H) :=
  iStartProof;
  first
  [ (* (?P → _) *)
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    eapply tac_impl_intro_persistent with _ H _ _ _; (* (i:=H) *)
      [apply _
      |apply _ ||
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       let P := match goal with |- IntoPersistent _ ?P _ => P end in
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       fail 1 "iIntro:" P "not persistent"
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      |env_reflexivity || fail 1 "iIntro:" H "not fresh"
      |]
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  | (* (?P -∗ _) *)
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    eapply tac_wand_intro_persistent with _ H _ _ _; (* (i:=H) *)
      [ apply _
      | apply _ ||
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       let P := match goal with |- IntoPersistent _ ?P _ => P end in
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       fail 1 "iIntro:" P "not persistent"
      |apply _ ||
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       let P := match goal with |- TCOr (Affine ?P) _ => P end in
       fail 1 "iIntro:" P "not affine and the goal not absorbing"
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      |env_reflexivity || fail 1 "iIntro:" H "not fresh"
      |]
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  | fail "iIntro: nothing to introduce" ].
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Local Tactic Notation "iIntro" "_" :=
  first
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  [ (* (?Q → _) *)
    iStartProof; eapply tac_impl_intro_drop;
    [ apply _ | ]
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  | (* (_ -∗ _) *)
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    iStartProof; eapply tac_wand_intro_drop;
      [ apply _
      | apply _ ||
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       let P := match goal with |- TCOr (Affine ?P) _ => P end in
       fail 1 "iIntro:" P "not affine and the goal not absorbing"
      |]
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  | (* (∀ _, _) *) iIntro (_)
  | fail 1 "iIntro: nothing to introduce" ].

Local Tactic Notation "iIntroForall" :=
  lazymatch goal with
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  | |-  _, ?P => fail (* actually an →, this is handled by iIntro below *)
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  | |-  _, _ => intro
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  | |- let _ := _ in _ => intro
  | |- _ =>
    iStartProof;
    lazymatch goal with
    | |- envs_entails _ ( x : _, _) => let x' := fresh x in iIntro (x')
    end
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  end.
Local Tactic Notation "iIntro" :=
  lazymatch goal with
  | |- _  ?P => intro
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  | |- _ =>
    iStartProof;
    lazymatch goal with
    | |- envs_entails _ (_ - _) => iIntro (?) || let H := iFresh in iIntro #H || iIntro H
    | |- envs_entails _ (_  _) => iIntro (?) || let H := iFresh in iIntro #H || iIntro H
    end
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  end.

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(** * Specialize *)
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Record iTrm {X As S} :=
  ITrm { itrm : X ; itrm_vars : hlist As ; itrm_hyps : S }.
Arguments ITrm {_ _ _} _ _ _.
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Notation "( H $! x1 .. xn )" :=
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  (ITrm H (hcons x1 .. (hcons xn hnil) ..) "") (at level 0, x1, xn at level 9).
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Notation "( H $! x1 .. xn 'with' pat )" :=
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  (ITrm H (hcons x1 .. (hcons xn hnil) ..) pat) (at level 0, x1, xn at level 9).
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Notation "( H 'with' pat )" := (ITrm H hnil pat) (at level 0).

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(** There is some hacky stuff going on here: because of Coq bug #6583, unresolved
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type classes in the arguments `xs` are resolved at arbitrary moments. Tactics
like `apply`, `split` and `eexists` wrongly trigger type class search to resolve
these holes. To avoid TC being triggered too eagerly, this tactic uses `refine`
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at most places instead of `apply`. *)
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Local Tactic Notation "iSpecializeArgs" constr(H) open_constr(xs) :=
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  let rec go xs :=
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    lazymatch xs with
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    | hnil => idtac
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    | hcons ?x ?xs =>
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       notypeclasses refine (tac_forall_specialize _ _ H _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H "not found"
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         |iSolveTC ||
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          let P := match goal with |- IntoForall ?P _ => P end in
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          fail "iSpecialize: cannot instantiate" P "with" x
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         |lazymatch goal with (* Force [A] in [ex_intro] to deal with coercions. *)
          | |-  _ : ?A, _ =>
            notypeclasses refine (@ex_intro A _ x (conj _ _))
          end; [shelve..|env_reflexivity|go xs]]
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    end in
  go xs.
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Local Tactic Notation "iSpecializePat" open_constr(H) constr(pat) :=
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  let solve_to_wand H1 :=
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    iSolveTC ||
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    let P := match goal with |- IntoWand _ _ ?P _ _ => P end in
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    fail "iSpecialize:" P "not an implication/wand" in
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  let solve_done d :=
    lazymatch d with
    | true =>
       done ||
       let Q := match goal with |- envs_entails _ ?Q => Q end in
       fail "iSpecialize: cannot solve" Q "using done"
    | false => idtac
    end in
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  let rec go H1 pats :=
    lazymatch pats with
    | [] => idtac
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    | SForall :: ?pats =>
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       idtac "[IPM] The * specialization pattern is deprecated because it is applied implicitly.";
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       go H1 pats
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    | SIdent ?H2 :: ?pats =>
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       notypeclasses refine (tac_specialize _ _ _ H2 _ H1 _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H2 "not found"
         |env_reflexivity || fail "iSpecialize:" H1 "not found"
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         |iSolveTC ||
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          let P := match goal with |- IntoWand _ _ ?P ?Q _ => P end in
          let Q := match goal with |- IntoWand _ _ ?P ?Q _ => Q end in
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          fail "iSpecialize: cannot instantiate" P "with" Q
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         |env_reflexivity|go H1 pats]
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    | SPureGoal ?d :: ?pats =>
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       notypeclasses refine (tac_specialize_assert_pure _ _ H1 _ _ _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H1 "not found"
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         |solve_to_wand H1
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         |iSolveTC ||
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          let Q := match goal with |- FromPure _ ?Q _ => Q end in
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          fail "iSpecialize:" Q "not pure"
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         |env_reflexivity
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         |solve_done d (*goal*)
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         |go H1 pats]
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    | SGoal (SpecGoal GPersistent false ?Hs_frame [] ?d) :: ?pats =>
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       notypeclasses refine (tac_specialize_assert_persistent _ _ _ H1 _ _ _ _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H1 "not found"
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         |solve_to_wand H1
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         |iSolveTC ||
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          let Q := match goal with |- Persistent ?Q => Q end in
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          fail "iSpecialize:" Q "not persistent"
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         |iSolveTC
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         |env_reflexivity
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         |iFrame Hs_frame; solve_done d (*goal*)
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         |go H1 pats]
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    | SGoal (SpecGoal GPersistent _ _ _ _) :: ?pats =>
       fail "iSpecialize: cannot select hypotheses for persistent premise"
    | SGoal (SpecGoal ?m ?lr ?Hs_frame ?Hs ?d) :: ?pats =>
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       let Hs' := eval cbv in (if lr then Hs else Hs_frame ++ Hs) in
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       notypeclasses refine (tac_specialize_assert _ _ _ _ H1 _ lr Hs' _ _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H1 "not found"
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         |solve_to_wand H1
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         |lazymatch m with
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          | GSpatial => notypeclasses refine (add_modal_id _ _)
          | GModal => iSolveTC || fail "iSpecialize: goal not a modality"
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          end
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         |env_reflexivity ||
          let Hs' := iMissingHyps Hs' in
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          fail "iSpecialize: hypotheses" Hs' "not found"
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         |iFrame Hs_frame; solve_done d (*goal*)
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         |go H1 pats]
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    | SAutoFrame GPersistent :: ?pats =>
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       notypeclasses refine (tac_specialize_assert_persistent _ _ _ H1 _ _ _ _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H1 "not found"
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         |solve_to_wand H1
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         |iSolveTC ||
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          let Q := match goal with |- Persistent ?Q => Q end in
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          fail "iSpecialize:" Q "not persistent"
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         |env_reflexivity
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         |solve [iFrame "∗ #"]
         |go H1 pats]
    | SAutoFrame ?m :: ?pats =>
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       notypeclasses refine (tac_specialize_frame _ _ H1 _ _ _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H1 "not found"
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         |solve_to_wand H1
         |lazymatch m with
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          | GSpatial => notypeclasses refine (add_modal_id _ _)
          | GModal => iSolveTC || fail "iSpecialize: goal not a modality"
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          end
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         |first
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            [notypeclasses refine (tac_unlock_emp _ _ _)
            |notypeclasses refine (tac_unlock_True _ _ _)
            |iFrame "∗ #"; notypeclasses refine (tac_unlock _ _ _)
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            |fail "iSpecialize: premise cannot be solved by framing"]
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         |exact eq_refl]; iIntro H1; go H1 pats
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    end in let pats := spec_pat.parse pat in go H pats.

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(* The argument [p] denotes whether the conclusion of the specialized term is
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persistent. If so, one can use all spatial hypotheses for both proving the
premises and the remaning goal. The argument [p] can either be a Boolean or an
introduction pattern, which will be coerced into [true] when it solely contains
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`#` or `%` patterns at the top-level.

In case the specialization pattern in [t] states that the modality of the goal
should be kept for one of the premises (i.e. [>[H1 .. Hn]] is used) then [p]
defaults to [false] (i.e. spatial hypotheses are not preserved). *)
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Tactic Notation "iSpecializeCore" open_constr(H)
    "with" open_constr(xs) open_constr(pat) "as" constr(p) :=
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  let p := intro_pat_persistent p in
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  let pat := spec_pat.parse pat in
  let H :=
    lazymatch type of H with
    | string => constr:(INamed H)
    | _ => H
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    end in
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  iSpecializeArgs H xs; [..|
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  lazymatch type of H with
  | ident =>
    (* The lemma [tac_specialize_persistent_helper] allows one to use all
    spatial hypotheses for both proving the premises of the lemma we
    specialize as well as those of the remaining goal. We can only use it when
    the result of the specialization is persistent, and no modality is
    eliminated. As an optimization, we do not use this when only universal
    quantifiers are instantiated. *)
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    let pat := spec_pat.parse pat in
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    lazymatch eval compute in
      (p && bool_decide (pat  []) && negb (existsb spec_pat_modal pat)) with
    | true =>
       (* FIXME: do something reasonable when the BI is not affine *)
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       notypeclasses refine (tac_specialize_persistent_helper _ _ H _ _ _ _ _ _ _ _ _ _ _);
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         [env_reflexivity || fail "iSpecialize:" H "not found"
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         |iSpecializePat H pat;
           [..
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           |refine (tac_specialize_persistent_helper_done _ H _ _ _);
            env_reflexivity]
         |iSolveTC ||
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          let Q := match goal with |- IntoPersistent _ ?Q _ => Q end in
          fail "iSpecialize:" Q "not persistent"
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         |env_cbv; iSolveTC ||
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          let Q := match goal with |- TCAnd _ (Affine ?Q) => Q end in
          fail "iSpecialize:" Q "not affine"
         |env_reflexivity
         |(* goal *)]
    | false => iSpecializePat H pat
    end
  | _ => fail "iSpecialize:" H "should be a hypothesis, use iPoseProof instead"
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  end].
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Tactic Notation "iSpecializeCore" open_constr(t) "as" constr(p) :=
  lazymatch type of t with
  | string => iSpecializeCore t with hnil "" as p
  | ident => iSpecializeCore t with hnil "" as p
  | _ =>
    lazymatch t with
    | ITrm ?H ?xs ?pat => iSpecializeCore H with xs pat as p
    | _ => fail "iSpecialize:" t "should be a proof mode term"
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    end
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  end.
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Tactic Notation "iSpecialize" open_constr(t) :=
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  iSpecializeCore t as false.
Tactic Notation "iSpecialize" open_constr(t) "as" "#" :=
  iSpecializeCore t as true.
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(** * Pose proof *)
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(* The tactic [iIntoEmpValid] tactic solves a goal [bi_emp_valid Q]. The
argument [t] must be a Coq term whose type is of the following shape:
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[∀ (x_1 : A_1) .. (x_n : A_n), φ]

and so that we have an instance `AsValid φ Q`.

Examples of such [φ]s are

- [bi_emp_valid P], in which case [Q] should be [P]
- [P1 ⊢ P2], in which case [Q] should be [P1 -∗ P2]
- [P1 ⊣⊢ P2], in which case [Q] should be [P1 ↔ P2]
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The tactic instantiates each dependent argument [x_i] with an evar and generates
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a goal [R] for each non-dependent argument [x_i : R].  For example, if the
original goal was [Q] and [t] has type [∀ x, P x → Q], then it generates an evar
[?x] for [x] and a subgoal [P ?x]. *)
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Tactic Notation "iIntoEmpValid" open_constr(t) :=
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  let rec go t :=
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    (* We try two reduction tactics for the type of t before trying to
       specialize it. We first try the head normal form in order to
       unfold all the definition that could hide an entailment.  Then,
       we try the much weaker [eval cbv zeta], because entailment is
       not necessarilly opaque, and could be unfolded by [hnf].

       However, for calling type class search, we only use [cbv zeta]
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       in order to make sure we do not unfold [bi_emp_valid]. *)
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    let tT := type of t in
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    first
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      [ let tT' := eval hnf in tT in go_specialize t tT'
      | let tT' := eval cbv zeta in tT in go_specialize t tT'
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      | let tT' := eval cbv zeta in tT in
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        notypeclasses refine (as_emp_valid_1 tT _ _);
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          [iSolveTC || fail "iPoseProof: not a BI assertion"
          |exact t]]
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  with go_specialize t tT :=
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    lazymatch tT with                (* We do not use hnf of tT, because, if
                                        entailment is not opaque, then it would
                                        unfold it. *)
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    | ?P  ?Q => let H := fresh in assert P as H; [|go uconstr:(t H); clear H]
    |  _ : ?T, _ =>
      (* Put [T] inside an [id] to avoid TC inference from being invoked. *)
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      (* This is a workarround for Coq bug #6583. *)
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      let e := fresh in evar (e:id T);
      let e' := eval unfold e in e in clear e; go (t e')
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    end
  in
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  go t.
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(* The tactic [tac] is called with a temporary fresh name [H]. The argument
[lazy_tc] denotes whether type class inference on the premises of [lem] should
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be performed before (if false) or after (if true) [tac H] is called.

The tactic [iApply] uses laxy type class inference, so that evars can first be
instantiated by matching with the goal, whereas [iDestruct] does not, because
eliminations may not be performed when type classes have not been resolved.
*)
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Tactic Notation "iPoseProofCore" open_constr(lem)
    "as" constr(p) constr(lazy_tc) tactic(tac) :=
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  iStartProof;
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  let Htmp := iFresh in
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  let t := lazymatch lem with ITrm ?t ?xs ?pat => t | _ => lem end in
  let t := lazymatch type of t with string => constr:(INamed t) | _ => t end in
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  let spec_tac _ :=
    lazymatch lem with
    | ITrm ?t ?xs ?pat => iSpecializeCore (ITrm Htmp xs pat) as p
    | _ => idtac
    end in
  let go goal_tac :=
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    lazymatch type of t with
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    | ident =>
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       eapply tac_pose_proof_hyp with _ _ t _ Htmp _;
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         [env_reflexivity || fail "iPoseProof:" t "not found"
         |env_reflexivity || fail "iPoseProof:" Htmp "not fresh"
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         |goal_tac ()]
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    | _ =>
       eapply tac_pose_proof with _ Htmp _; (* (j:=H) *)
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         [iIntoEmpValid t
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         |env_reflexivity || fail "iPoseProof:" Htmp "not fresh"
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         |goal_tac ()]
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    end;
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    try iSolveTC in
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  lazymatch eval compute in lazy_tc with
  | true => go ltac:(fun _ => spec_tac (); last (tac Htmp))
  | false => go spec_tac; last (tac Htmp)
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  end.

(** * Apply *)
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Tactic Notation "iApplyHyp" constr(H) :=
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  let rec go H := first
    [eapply tac_apply with _ H _ _ _;
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      [env_reflexivity
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      |iSolveTC
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      |lazy beta (* reduce betas created by instantiation *)]
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    |iSpecializePat H "[]"; last go H] in
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  iExact H ||
  go H ||
  lazymatch iTypeOf H with
  | Some (_,?Q) => fail "iApply: cannot apply" Q
  end.

Tactic Notation "iApply" open_constr(lem) :=
  iPoseProofCore lem as false true (fun H => iApplyHyp H).
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(** * Revert *)
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Local Tactic Notation "iForallRevert" ident(x) :=
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  let err x :=
    intros x;
    iMatchHyp (fun H P =>
      lazymatch P with
      | context [x] => fail 2 "iRevert:" x "is used in hypothesis" H
      end) in
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  iStartProof;
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  let A := type of x in
  lazymatch type of A with
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  | Prop => revert x; first [apply tac_pure_revert|err x]
  | _ => revert x; first [apply tac_forall_revert|err x]
  end.
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Tactic Notation "iRevert" constr(Hs) :=
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  let rec go Hs :=
    lazymatch Hs with
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    | [] => idtac
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    | ESelPure :: ?Hs =>
       repeat match goal with x : _ |- _ => revert x end;
       go Hs
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    | ESelIdent _ ?H :: ?Hs =>
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       eapply tac_revert with _ H _ _; (* (i:=H2) *)
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         [env_reflexivity || fail "iRevert:" H "not found"
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         |env_cbv; go Hs]
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    end in