Merge branch 'v8.6'

2 files changed, 24 insertions, 0 deletions

diff --git a/engine/proofview.ml b/engine/proofview.ml
index 51b3a7260a..1ebc857d85 100644
--- a/engine/proofview.ml
+++ b/engine/proofview.ml
@@ -1058,6 +1058,26 @@ module Goal = struct
     end
     end
 
+  exception NotExactlyOneSubgoal
+  let _ = CErrors.register_handler begin function
+  | NotExactlyOneSubgoal ->
+      CErrors.user_err (Pp.str"Not exactly one subgoal.")
+  | _ -> raise CErrors.Unhandled
+  end
+
+  let enter_one f =
+    let open Proof in
+    Comb.get >>= function
+    | [goal] -> begin
+       Env.get >>= fun env ->
+       tclEVARMAP >>= fun sigma ->
+       try f.enter (gmake env sigma goal)
+       with e when catchable_exception e ->
+         let (e, info) = CErrors.push e in
+         tclZERO ~info e
+      end
+    | _ -> tclZERO NotExactlyOneSubgoal
+
   type ('a, 'b) s_enter =
     { s_enter : 'r. ('a, 'r) t -> ('b, 'r) Sigma.sigma }
 
diff --git a/engine/proofview.mli b/engine/proofview.mli
index 901cf26e0e..bc68f11ff0 100644
--- a/engine/proofview.mli
+++ b/engine/proofview.mli
@@ -499,6 +499,10 @@ module Goal : sig
   (** Like {!nf_enter}, but does not normalize the goal beforehand. *)
   val enter : ([ `LZ ], unit tactic) enter -> unit tactic
 
+  (** Like {!enter}, but assumes exactly one goal under focus, raising *)
+  (** an error otherwise. *)
+  val enter_one : ([ `LZ ], 'a tactic) enter -> 'a tactic
+
   type ('a, 'b) s_enter =
     { s_enter : 'r. ('a, 'r) t -> ('b, 'r) Sigma.sigma }