Better operator overloading inference

This commit introduces a weak form a bi-directional typing, and
does a two-pass typing of overloading operators arguments.

src/ecHiInductive.ml

@@ -284,7 +284,7 @@ let trans_matchfix
           let filter = fun _ op -> EcDecl.is_ctor op in
           let PPApp ((cname, tvi), cargs) = pb.pop_pattern in
           let tvi = tvi |> omap (TT.transtvi env ue) in
-          let cts = EcUnify.select_op ~filter tvi env (unloc cname) ue [] in
+          let cts = EcUnify.select_op ~filter tvi env (unloc cname) ue ([], None) in
 
           match cts with
           | [] ->

src/ecPrinting.ml

@@ -941,7 +941,7 @@ let pp_opapp
       (es      : 'a list))
 =
   let (nm, opname) =
-    PPEnv.op_symb ppe op (Some (pred, tvi, List.map t_ty es)) in
+    PPEnv.op_symb ppe op (Some (pred, tvi, (List.map t_ty es, None))) in
 
   let inm = if nm = [] then fst outer else nm in
 
@@ -1250,7 +1250,7 @@ let pp_chained_orderings (ppe : PPEnv.t) t_ty pp_sub outer fmt (f, fs) =
         ignore (List.fold_left
           (fun fe (op, tvi, f) ->
             let (nm, opname) =
-              PPEnv.op_symb ppe op (Some (`Form, tvi, [t_ty fe; t_ty f]))
+              PPEnv.op_symb ppe op (Some (`Form, tvi, ([t_ty fe; t_ty f], None)))
             in
               Format.fprintf fmt " %t@ %a"
                 (fun fmt ->
@@ -1343,7 +1343,7 @@ let lower_left (ppe : PPEnv.t) (t_ty : form -> EcTypes.ty) (f : form)
         else l_l f2 onm e_bin_prio_rop4
     | Fapp ({f_node = Fop (op, tys)}, [f1; f2]) ->
         (let (inm, opname) =
-           PPEnv.op_symb ppe op (Some (`Form, tys, List.map t_ty [f1; f2])) in
+           PPEnv.op_symb ppe op (Some (`Form, tys, (List.map t_ty [f1; f2], None))) in
          if inm <> [] && inm <> onm
          then None
          else match priority_of_binop opname with

src/ecScope.ml

@@ -1689,7 +1689,7 @@ module Ty = struct
         let tvi = List.map (TT.transty tp_tydecl env ue) tvi in
         let selected =
           EcUnify.select_op ~filter:(fun _ -> EcDecl.is_oper)
-            (Some (EcUnify.TVIunamed tvi)) env (unloc op) ue []
+            (Some (EcUnify.TVIunamed tvi)) env (unloc op) ue ([], None)
         in
         let op =
           match selected with

src/ecTyping.ml

@@ -300,15 +300,15 @@ let select_local env (qs,s) =
   else None
 
 (* -------------------------------------------------------------------- *)
-let select_pv env side name ue tvi psig =
+let select_pv env side name ue tvi (psig, retty) =
   if   tvi <> None
   then []
   else
     try
       let pvs = EcEnv.Var.lookup_progvar ?side name env in
       let select (pv,ty) =
         let subue = UE.copy ue in
-        let texpected = EcUnify.tfun_expected subue psig in
+        let texpected = EcUnify.tfun_expected subue ?retty psig in
           try
             EcUnify.unify env subue ty texpected;
             [(pv, ty, subue)]
@@ -346,7 +346,7 @@ let gen_select_op
     (env      : EcEnv.env)
     (name     : EcSymbols.qsymbol)
     (ue       : EcUnify.unienv)
-    (psig     : EcTypes.dom)
+    (psig     : EcTypes.dom * EcTypes.ty option)
 
     : OpSelect.gopsel list
 =
@@ -432,7 +432,7 @@ let select_form_op env mode ~forcepv opsc name ue tvi psig =
 (* -------------------------------------------------------------------- *)
 let select_proj env opsc name ue tvi recty =
   let filter = (fun _ op -> EcDecl.is_proj op) in
-  let ops = EcUnify.select_op ~filter tvi env name ue [recty] in
+  let ops = EcUnify.select_op ~filter tvi env name ue ([recty], None) in
   let ops = List.map (fun (p, ty, ue, _) -> (p, ty, ue)) ops in
 
   match ops, opsc with
@@ -1060,7 +1060,7 @@ let transpattern1 env ue (p : EcParsetree.plpattern) =
       let fields =
         let for1 (name, v) =
           let filter = fun _ op -> EcDecl.is_proj op in
-          let fds    = EcUnify.select_op ~filter None env (unloc name) ue [] in
+          let fds    = EcUnify.select_op ~filter None env (unloc name) ue ([], None) in
             match List.ohead fds with
             | None ->
               let exn = UnknownRecFieldName (unloc name) in
@@ -1200,7 +1200,7 @@ let trans_record env ue (subtt, proj) (loc, b, fields) =
     let for1 rf =
       let filter = fun _ op -> EcDecl.is_proj op in
       let tvi    = rf.rf_tvi |> omap (transtvi env ue) in
-      let fds    = EcUnify.select_op ~filter tvi env (unloc rf.rf_name) ue [] in
+      let fds    = EcUnify.select_op ~filter tvi env (unloc rf.rf_name) ue ([], None) in
         match List.ohead fds with
         | None ->
             let exn = UnknownRecFieldName (unloc rf.rf_name) in
@@ -1289,7 +1289,7 @@ let trans_branch ~loc env ue gindty ((pb, body) : ppattern * _) =
   let filter = fun _ op -> EcDecl.is_ctor op in
   let PPApp ((cname, tvi), cargs) = pb in
   let tvi = tvi |> omap (transtvi env ue) in
-  let cts = EcUnify.select_op ~filter tvi env (unloc cname) ue [] in
+  let cts = EcUnify.select_op ~filter tvi env (unloc cname) ue ([], None) in
 
   match cts with
   | [] ->
@@ -2512,7 +2512,7 @@ and translvalue ue (env : EcEnv.env) lvalue =
       let e, ety = e_tuple e, ttuple ety in
       let name = ([], EcCoreLib.s_set) in
       let esig = [xty; ety; codomty] in
-      let ops = select_exp_op env `InProc None name ue tvi esig in
+      let ops = select_exp_op env `InProc None name ue tvi (esig, None) in
 
       match ops with
       | [] ->
@@ -2581,8 +2581,9 @@ and trans_gbinding env ue decl =
 and trans_form_or_pattern env mode ?mv ?ps ue pf tt =
   let state = PFS.create () in
 
-  let rec transf_r opsc env f =
-    let transf = transf_r opsc in
+  let rec transf_r_tyinfo opsc env ?tt f =
+    let transf env ?tt f =
+      transf_r opsc env ?tt f in
 
     match f.pl_desc with
     | PFhole -> begin
@@ -2814,20 +2815,18 @@ and trans_form_or_pattern env mode ?mv ?ps ue pf tt =
     | PFdecimal (n, f) ->
         f_decimal (n, f)
 
-    | PFtuple args -> begin
-        let args = List.map (transf env) args in
-          match args with
-          | []  -> f_tt
-          | [f] -> f
-          | fs  -> f_tuple fs
-    end
+    | PFtuple pes ->        
+        let esig = List.map (fun _ -> EcUnify.UniEnv.fresh ue) pes in
+        tt |> oiter (fun tt -> unify_or_fail env ue f.pl_loc  ~expct:tt (ttuple esig));
+        let es = List.map2 (fun tt pe -> transf env ~tt pe) esig pes in
+        f_tuple es
 
     | PFident ({ pl_desc = name; pl_loc = loc }, tvi) ->
         let tvi = tvi |> omap (transtvi env ue) in
         let ops =
           select_form_op
             ~forcepv:(PFS.isforced state)
-            env mode opsc name ue tvi [] in
+            env mode opsc name ue tvi ([], tt) in
         begin match ops with
         | [] ->
             tyerror loc env (UnknownVarOrOp (name, []))
@@ -2962,13 +2961,43 @@ and trans_form_or_pattern env mode ?mv ?ps ue pf tt =
           check_mem f.pl_loc EcFol.mright;
           EcFol.f_ands (List.map (do1 (EcFol.mleft, EcFol.mright)) fs)
 
-    | PFapp ({pl_desc = PFident ({ pl_desc = name; pl_loc = loc }, tvi)}, pes) ->
+    | PFapp ({pl_desc = PFident ({ pl_desc = name; pl_loc = loc }, tvi)}, pes) -> begin
+      let try_trans ?tt pe =
+        let ue' = EcUnify.UniEnv.copy ue in
+        let ps' = Option.map (fun ps -> ref !ps) ps in
+          match transf env ?tt pe with
+          | e -> Some e
+          | exception TyError (_, _, MultipleOpMatch _) ->
+            Option.iter (fun ps -> ps := !(Option.get ps')) ps;
+            EcUnify.UniEnv.restore ~dst:ue ~src:ue';
+            None
+      in
+
+      match
+        let ue'  = EcUnify.UniEnv.copy ue in
+        let ps'  = Option.map (fun ps -> ref !ps) ps in
+        let es   = List.map (fun pe -> try_trans pe) pes in
+        let tvi  = tvi |> omap (transtvi env ue) in
+        let esig = List.map (fun e ->
+            match e with Some e -> e.f_ty | None -> EcUnify.UniEnv.fresh ue
+          ) es in
+        match
+          select_form_op ~forcepv:(PFS.isforced state)
+            env mode opsc name ue tvi (esig, tt)
+        with
+        | [sel] -> Some (sel, (es, esig, tvi))
+        | _ ->
+            Option.iter (fun ps -> ps := !(Option.get ps')) ps;
+            EcUnify.UniEnv.restore ~dst:ue ~src:ue';
+            None
+      with
+      | None -> begin
         let tvi  = tvi |> omap (transtvi env ue) in
         let es   = List.map (transf env) pes in
         let esig = List.map EcFol.f_ty es in
         let ops  =
           select_form_op ~forcepv:(PFS.isforced state)
-            env mode opsc name ue tvi esig in
+            env mode opsc name ue tvi (esig, tt) in
 
           begin match ops with
           | [] ->
@@ -2986,6 +3015,24 @@ and trans_form_or_pattern env mode ?mv ?ps ue pf tt =
              let matches = List.map (fun (_, _, subue, m) -> (m, subue)) ops in
              tyerror loc env (MultipleOpMatch (name, esig, matches))
           end
+        end
+
+      | Some ((_, _, subue, _) as sel, (es, esig, _tvi)) ->
+        EcUnify.UniEnv.restore ~dst:ue ~src:subue;
+        let es =
+          List.map2 (
+            fun (e, ty) pe ->
+              match e with None -> try_trans ~tt:ty pe | Some e -> Some e
+          ) (List.combine es esig) pes in
+          let es =
+            List.map2 (
+              fun (e, ty) pe ->
+                match e with None -> transf env ~tt:ty pe | Some e -> e
+            ) (List.combine es esig) pes in
+          let es = List.map2 (fun e l -> mk_loc l.pl_loc e) es pes in
+        EcUnify.UniEnv.restore ~src:ue ~dst:subue;
+        form_of_opselect (env, ue) loc sel es
+      end
 
     | PFapp (e, pes) ->
         let es    = List.map (transf env) pes in
@@ -3041,25 +3088,30 @@ and trans_form_or_pattern env mode ?mv ?ps ue pf tt =
         let f1 = transf env pf1 in
         unify_or_fail env ue pf1.pl_loc ~expct:pty f1.f_ty;
         aty |> oiter (fun aty-> unify_or_fail env ue pf1.pl_loc ~expct:pty aty);
-        let f2 = transf penv f2 in
+        let f2 = transf penv ?tt f2 in
         f_let p f1 f2
 
     | PFforall (xs, pf) ->
         let env, xs = trans_gbinding env ue xs in
         let f = transf env pf in
-          unify_or_fail env ue pf.pl_loc ~expct:tbool f.f_ty;
-          f_forall xs f
+        unify_or_fail env ue pf.pl_loc ~expct:tbool f.f_ty;
+        f_forall xs f
 
     | PFexists (xs, f1) ->
         let env, xs = trans_gbinding env ue xs in
         let f = transf env f1 in
-          unify_or_fail env ue f1.pl_loc ~expct:tbool f.f_ty;
-          f_exists xs f
+        unify_or_fail env ue f1.pl_loc ~expct:tbool f.f_ty;
+        f_exists xs f
 
     | PFlambda (xs, f1) ->
         let env, xs = trans_binding env ue xs in
-        let f = transf env f1 in
-          f_lambda (List.map (fun (x,ty) -> (x,GTty ty)) xs) f
+        let subtt = tt |> Option.map (fun tt ->
+          let codom = EcUnify.UniEnv.fresh ue in
+          unify_or_fail env ue (loc f) ~expct:(toarrow (List.snd xs) codom) tt;
+          codom
+        ) in
+        let f = transf env ?tt:subtt f1 in
+        f_lambda (List.map (fun (x, ty) -> (x, GTty ty)) xs) f
 
     | PFrecord (b, fields) ->
         let (ctor, fields, (rtvi, reccty)) =
@@ -3190,11 +3242,12 @@ and trans_form_or_pattern env mode ?mv ?ps ue pf tt =
         unify_or_fail qenv ue post.pl_loc ~expct:tbool post'.f_ty;
         f_eagerF pre' s1 fpath1 fpath2 s2 post'
 
-  in
+  and transf_r opsc env ?tt pf =
+    let f  = transf_r_tyinfo opsc env ?tt pf in
+    let () = oiter (fun tt -> unify_or_fail env ue pf.pl_loc ~expct:tt f.f_ty) tt in
+    f
 
-  let f = transf_r None env pf in
-  tt |> oiter (fun tt -> unify_or_fail env ue pf.pl_loc ~expct:tt f.f_ty);
-  f
+  in transf_r None env ?tt pf
 
 (* Type-check a memtype. *)
 and trans_memtype env ue (pmemtype : pmemtype) : memtype =

src/ecUnify.ml

@@ -396,15 +396,15 @@ let hastc env ue ty tc =
     ue := { !ue with ue_uf = uf; }
 
 (* -------------------------------------------------------------------- *)
-let tfun_expected ue psig =
-  let tres = UniEnv.fresh ue in
-    EcTypes.toarrow psig tres
+let tfun_expected ue ?retty psig =
+  let retty = ofdfl (fun () -> UniEnv.fresh ue) retty in
+  EcTypes.toarrow psig retty
 
 (* -------------------------------------------------------------------- *)
 type sbody = ((EcIdent.t * ty) list * expr) Lazy.t
 
 (* -------------------------------------------------------------------- *)
-let select_op ?(hidden = false) ?(filter = fun _ _ -> true) tvi env name ue psig =
+let select_op ?(hidden = false) ?(filter = fun _ _ -> true) tvi env name ue (psig, retty) =
   ignore hidden;                (* FIXME *)
 
   let module D = EcDecl in
@@ -457,7 +457,7 @@ let select_op ?(hidden = false) ?(filter = fun _ _ -> true) tvi env name ue psig
 
       let (tip, tvs) = UniEnv.openty_r subue op.D.op_tparams tvi in
       let top = ty_subst tip op.D.op_ty in
-      let texpected = tfun_expected subue psig in
+      let texpected = tfun_expected subue ?retty psig in
 
       (try  unify env subue top texpected
        with UnificationFailure _ -> raise E.Failure);

src/ecUnify.mli

@@ -37,7 +37,7 @@ end
 val unify : EcEnv.env -> unienv -> ty -> ty -> unit
 val hastc : EcEnv.env -> unienv -> ty -> Sp.t -> unit
 
-val tfun_expected : unienv -> EcTypes.ty list -> EcTypes.ty
+val tfun_expected : unienv -> ?retty:ty -> EcTypes.ty list -> EcTypes.ty
 
 type sbody = ((EcIdent.t * ty) list * expr) Lazy.t
 
@@ -48,5 +48,5 @@ val select_op :
   -> EcEnv.env
   -> qsymbol
   -> unienv
-  -> dom
+  -> dom * ty option
   -> ((EcPath.path * ty list) * ty * unienv * sbody option) list

tests/overloading.ec

@@ -0,0 +1,24 @@
+require import AllCore List.
+
+theory T.
+  op o : int.
+  op a : int -> int -> int.
+end T.
+
+theory U.
+  op o : bool.
+  op a : bool -> bool -> bool.
+end U.
+
+import T U.
+
+op foo : int -> unit.
+
+op bar = foo o.
+
+op plop1 = foldr a false [].
+
+op plop2 = foldr (fun x => a x) false [].
+
+op plop3 = foldr (fun x y => a x y) false [].
+