4 files changed, 67 insertions, 24 deletions
diff --git a/theories/Compat/Coq84.v b/theories/Compat/Coq84.v
index 90083b00..a3e23f91 100644
--- a/theories/Compat/Coq84.v
+++ b/theories/Compat/Coq84.v
@@ -7,6 +7,10 @@
 (************************************************************************)
 
 (** Compatibility file for making Coq act similar to Coq v8.4 *)
+
+(** Any compatibility changes to make future versions of Coq behave like Coq 8.5 are likely needed to make them behave like Coq 8.4. *)
+Require Export Coq.Compat.Coq85.
+
 (** See https://coq.inria.fr/bugs/show_bug.cgi?id=4319 for updates *)
 (** This is required in Coq 8.5 to use the [omega] tactic; in Coq 8.4, it's automatically available.  But ZArith_base puts infix ~ at level 7, and we don't want that, so we don't [Import] it. *)
 Require Coq.omega.Omega.
@@ -15,21 +19,31 @@ Ltac omega := Coq.omega.Omega.omega.
 (** The number of arguments given in [match] statements has changed from 8.4 to 8.5. *)
 Global Set Asymmetric Patterns.
 
+(** The automatic elimination schemes for records were dropped by default in 8.5.  This restores the default behavior of Coq 8.4. *)
+Global Set Nonrecursive Elimination Schemes.
+
 (** See bug 3545 *)
 Global Set Universal Lemma Under Conjunction.
 
-(** In 8.5, [refine] leaves over dependent subgoals. *)
-Tactic Notation "refine" uconstr(term) := refine term; shelve_unifiable.
+(** Feature introduced in 8.5, disabled by default and configurable since 8.6. *)
+Global Unset Refolding Reduction.
 
 (** In 8.4, [constructor (tac)] allowed backtracking across the use of [constructor]; it has been subsumed by [constructor; tac]. *)
-Ltac constructor_84 := constructor.
 Ltac constructor_84_n n := constructor n.
 Ltac constructor_84_tac tac := once (constructor; tac).
 
-Tactic Notation "constructor" := constructor_84.
+Tactic Notation "constructor" := Coq.Init.Notations.constructor.
 Tactic Notation "constructor" int_or_var(n) := constructor_84_n n.
 Tactic Notation "constructor" "(" tactic(tac) ")" := constructor_84_tac tac.
 
+(** In 8.4, [econstructor (tac)] allowed backtracking across the use of [econstructor]; it has been subsumed by [econstructor; tac]. *)
+Ltac econstructor_84_n n := econstructor n.
+Ltac econstructor_84_tac tac := once (econstructor; tac).
+
+Tactic Notation "econstructor" := Coq.Init.Notations.econstructor.
+Tactic Notation "econstructor" int_or_var(n) := econstructor_84_n n.
+Tactic Notation "econstructor" "(" tactic(tac) ")" := econstructor_84_tac tac.
+
 (** Some tactic notations do not factor well with tactics; we add global parsing entries for some tactics that would otherwise be overwritten by custom variants. See https://coq.inria.fr/bugs/show_bug.cgi?id=4392. *)
 Tactic Notation "reflexivity" := reflexivity.
 Tactic Notation "assumption" := assumption.
@@ -45,29 +59,21 @@ Tactic Notation "left" := left.
 Tactic Notation "eleft" := eleft.
 Tactic Notation "right" := right.
 Tactic Notation "eright" := eright.
-Tactic Notation "constructor" := constructor.
-Tactic Notation "econstructor" := econstructor.
 Tactic Notation "symmetry" := symmetry.
 Tactic Notation "split" := split.
 Tactic Notation "esplit" := esplit.
 
-Global Set Regular Subst Tactic.
-
-(** Some names have changed in the standard library, so we add aliases. *)
-Require Coq.ZArith.Int.
-Module Export Coq.
-  Module Export ZArith.
-    Module Int.
-      Module Z_as_Int.
-        Include Coq.ZArith.Int.Z_as_Int.
-        (* FIXME: Should these get a (compat "8.4")?  Or be moved to Z_as_Int, probably? *)
-        Notation plus := Coq.ZArith.Int.Z_as_Int.add (only parsing).
-        Notation minus := Coq.ZArith.Int.Z_as_Int.sub (only parsing).
-        Notation mult := Coq.ZArith.Int.Z_as_Int.mul (only parsing).
-      End Z_as_Int.
-    End Int.
-  End ZArith.
-End Coq.
-
 (** Many things now import [PeanoNat] rather than [NPeano], so we require it so that the old absolute names in [NPeano.Nat] are available. *)
 Require Coq.Numbers.Natural.Peano.NPeano.
+
+(** The following coercions were declared by default in Specif.v. *)
+Coercion sig_of_sig2 : sig2 >-> sig.
+Coercion sigT_of_sigT2 : sigT2 >-> sigT.
+Coercion sigT_of_sig : sig >-> sigT.
+Coercion sig_of_sigT : sigT >-> sig.
+Coercion sigT2_of_sig2 : sig2 >-> sigT2.
+Coercion sig2_of_sigT2 : sigT2 >-> sig2.
+
+(** In 8.4, the statement of admitted lemmas did not depend on the section
+    variables. *)
+Unset Keep Admitted Variables.
diff --git a/theories/Compat/Coq85.v b/theories/Compat/Coq85.v
index 6e2b3564..64ba6b1e 100644
--- a/theories/Compat/Coq85.v
+++ b/theories/Compat/Coq85.v
@@ -7,3 +7,30 @@
 (************************************************************************)
 
 (** Compatibility file for making Coq act similar to Coq v8.5 *)
+
+(** Any compatibility changes to make future versions of Coq behave like Coq 8.6
+    are likely needed to make them behave like Coq 8.5. *)
+Require Export Coq.Compat.Coq86.
+
+(** We use some deprecated options in this file, so we disable the
+    corresponding warning, to silence the build of this file. *)
+Local Set Warnings "-deprecated-option".
+
+(* In 8.5, "intros [|]", taken e.g. on a goal "A\/B->C", does not
+   behave as "intros [H|H]" but leave instead hypotheses quantified in
+   the goal, here producing subgoals A->C and B->C. *)
+
+Global Unset Bracketing Last Introduction Pattern.
+Global Unset Regular Subst Tactic.
+Global Unset Structural Injection.
+Global Unset Shrink Abstract.
+Global Unset Shrink Obligations.
+Global Set Refolding Reduction.
+
+(** The resolution algorithm for type classes has changed. *)
+Global Set Typeclasses Legacy Resolution.
+Global Set Typeclasses Limit Intros.
+Global Unset Typeclasses Filtered Unification.
+
+(** Allow silently letting unification constraints float after a "." *)
+Global Unset Solve Unification Constraints.
diff --git a/theories/Compat/Coq86.v b/theories/Compat/Coq86.v
new file mode 100644
index 00000000..6952fdf1
--- /dev/null
+++ b/theories/Compat/Coq86.v
@@ -0,0 +1,9 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2016     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(** Compatibility file for making Coq act similar to Coq v8.6 *)
+\ No newline at end of file
diff --git a/theories/Compat/vo.itarget b/theories/Compat/vo.itarget
index 43b19700..7ffb86eb 100644
--- a/theories/Compat/vo.itarget
+++ b/theories/Compat/vo.itarget
@@ -1,3 +1,4 @@
 AdmitAxiom.vo
 Coq84.vo
 Coq85.vo
+Coq86.vo