Merge branch 'robbert/iRevert_pure' into 'master'

Let `iRevert` of a pure hypotheses generate a wand instead of implication.

See merge request iris/iris!789

CHANGELOG.md

@@ -21,6 +21,8 @@ lemma.
   the conclusion. The old behavior can be emulated with`iExFalso. iExact "H".`
 * In `iInduction`, support induction schemes that involve `Forall` and
   `Forall2` (for example, for trees with finite branching).
+* Change `iRevert` of a pure hypothesis to generate a magic wand instead of an
+  implication.
 
 **Changes in `base_logic`:**
 

iris/proofmode/coq_tactics.v

@@ -170,8 +170,14 @@ Proof.
       rewrite -persistent_and_affinely_sep_l. apply pure_elim_l=> ?. by rewrite HQ.
 Qed.
 
-Lemma tac_pure_revert Δ φ Q : envs_entails Δ (⌜φ⌝ → Q) → (φ → envs_entails Δ Q).
-Proof. rewrite envs_entails_eq. intros HΔ ?. by rewrite HΔ pure_True // left_id. Qed.
+Lemma tac_pure_revert Δ φ P Q :
+  FromAffinely P ⌜ φ ⌝ →
+  envs_entails Δ (P -∗ Q) →
+  (φ → envs_entails Δ Q).
+Proof.
+  rewrite /FromAffinely envs_entails_eq. intros <- -> ?.
+  by rewrite pure_True // affinely_True_emp affinely_emp left_id.
+Qed.
 
 (** * Intuitionistic *)
 Lemma tac_intuitionistic Δ i j p P P' Q :

iris/proofmode/ltac_tactics.v

@@ -651,7 +651,10 @@ Local Tactic Notation "iForallRevert" ident(x) :=
   first [let A := type of x in idtac|fail 1 "iRevert:" x "not in scope"];
   let A := type of x in
   lazymatch type of A with
-  | Prop => revert x; first [apply tac_pure_revert|err x]
+  | Prop =>
+     revert x; first
+       [eapply tac_pure_revert; [iSolveTC (* [FromAffinely], should never fail *)|]
+       |err x]
   | _ => revert x; first [apply tac_forall_revert|err x]
   end.
 

tests/proofmode.ref

@@ -408,6 +408,29 @@ No applicable tactic.
   "HQ" : Q
   --------------------------------------∗
   ▷ P ∗ Q
+"test_iRevert_pure"
+     : string
+1 goal
+  
+  PROP : bi
+  φ : Prop
+  P : PROP
+  ============================
+  "H" : <affine> ⌜φ⌝ -∗ P
+  --------------------------------------∗
+  <affine> ⌜φ⌝ -∗ P
+"test_iRevert_pure_affine"
+     : string
+1 goal
+  
+  PROP : bi
+  BiAffine0 : BiAffine PROP
+  φ : Prop
+  P : PROP
+  ============================
+  "H" : ⌜φ⌝ -∗ P
+  --------------------------------------∗
+  ⌜φ⌝ -∗ P
 "elim_mod_accessor"
      : string
 1 goal

tests/proofmode.v

@@ -1157,6 +1157,22 @@ Proof.
   iIntros (?) "HP HQ". iModIntro. Show. by iFrame.
 Qed.
 
+Check "test_iRevert_pure".
+Lemma test_iRevert_pure (φ : Prop) P :
+  φ → (<affine> ⌜ φ ⌝ -∗ P) -∗ P.
+Proof.
+  (* Check that iRevert creates a wand instead of an implication *)
+  iIntros (Hφ) "H". iRevert (Hφ). Show. done.
+Qed.
+
+Check "test_iRevert_pure_affine".
+Lemma test_iRevert_pure_affine `{!BiAffine PROP} (φ : Prop) P :
+  φ → (⌜ φ ⌝ -∗ P) -∗ P.
+Proof.
+  (* If the BI is affine, no affine modality should be added *)
+  iIntros (Hφ) "H". iRevert (Hφ). Show. done.
+Qed.
+
 End tests.
 
 Section parsing_tests.