Refine test for unresolved evars: not reachable from initial evars

The test is refined to handle aliases: i.e. undefined evars coming from
restrictions and evar-evar unifications with an initial evar are not
considered fresh unresolved evars. To check this, we generalize the
restricted_evars set to an aliased_evars set in the evar map,
registering evars being solved by another evar due to restriction
or evar-evar unifications. This implements the proposal of PR #370
for testing the resolution status of evars independently of the evar-evar
orientation order.

This allows [apply] to refine an evar with a new one if it results from a
[clear] request or an evar-evar solution only, otherwise the new evar is
considered fresh and an error is raised.

Also fixes bugs #4095 and #4413.

Co-authored-by: Maxime Dénès <maxime.denes@inria.fr>

2 files changed, 15 insertions, 8 deletions

diff --git a/tactics/tacticals.ml b/tactics/tacticals.ml
index fc099f643d..c0fad0026f 100644
--- a/tactics/tacticals.ml
+++ b/tactics/tacticals.ml
@@ -695,6 +695,8 @@ module New = struct
   (* Check that holes in arguments have been resolved *)
 
   let check_evars env sigma extsigma origsigma =
+    let reachable = lazy (Evarutil.reachable_from_evars sigma
+                            (Evar.Map.domain (Evd.undefined_map origsigma))) in
     let rec is_undefined_up_to_restriction sigma evk =
       if Evd.mem origsigma evk then None else
       let evi = Evd.find sigma evk in
@@ -710,7 +712,12 @@ module New = struct
     let rest =
       Evd.fold_undefined (fun evk evi acc ->
         match is_undefined_up_to_restriction sigma evk with
-        | Some (evk',evi) -> (evk',evi)::acc
+        | Some (evk',evi) ->
+           (* If [evk'] descends from [evk] which descends itself from
+              an originally undefined evar in [origsigma], it is a not
+              a fresh undefined hole from [sigma]. *)
+           if Evar.Set.mem evk (Lazy.force reachable) then acc
+           else (evk',evi)::acc
         | _ -> acc)
         extsigma []
     in
diff --git a/tactics/tactics.ml b/tactics/tactics.ml
index 5f7e35d205..1dded80d92 100644
--- a/tactics/tactics.ml
+++ b/tactics/tactics.ml
@@ -5184,14 +5184,14 @@ end
 
 (** Tacticals defined directly in term of Proofview *)
 module New = struct
-  open Genredexpr
-  open Locus
-
   let reduce_after_refine =
-    reduce
-      (Lazy {rBeta=true;rMatch=true;rFix=true;rCofix=true;
-             rZeta=false;rDelta=false;rConst=[]})
-      {onhyps = Some []; concl_occs = AllOccurrences }
+    (* For backward compatibility reasons, we do not contract let-ins, but we unfold them. *)
+    let redfun env t =
+      let open CClosure in
+      let flags = RedFlags.red_add_transparent allnolet TransparentState.empty in
+      clos_norm_flags flags env t
+    in
+    reduct_in_concl ~check:false (redfun,DEFAULTcast)
 
   let refine ~typecheck c =
     Refine.refine ~typecheck c <*>