make ppx_deriving 4.1 build under 4.06

There is a lot of repetitive workarounds to the fact that Rtag labels
are now located, while {Exp,Pat}.variant labels are not. Ideally it
would have been cleaner if the upstream AST consistently used located
labels.

src_plugins/ppx_deriving_enum.cppo.ml

@@ -47,7 +47,10 @@ let mappings_of_type type_decl =
             raise_errorf ~loc:ptyp_loc
                          "%s cannot be derived for inherited variant cases" deriver
           | Rtag (name, attrs, true, []) ->
-            map acc mappings attrs { txt = name; loc = ptyp_loc }
+#if OCAML_VERSION < (4, 06, 0)
+            let name = mkloc name ptyp_loc in
+#endif
+            map acc mappings attrs name
           | Rtag _ ->
             raise_errorf ~loc:ptyp_loc
                          "%s can be derived only for argumentless constructors" deriver)

src_plugins/ppx_deriving_eq.cppo.ml

@@ -121,11 +121,18 @@ and expr_of_typ quoter typ =
       let cases =
         (fields |> List.map (fun field ->
           let pdup f = ptuple [f "lhs"; f "rhs"] in
+          let variant label popt =
+#if OCAML_VERSION < (4, 06, 0)
+            Pat.variant label popt
+#else
+            Pat.variant label.txt popt
+#endif
+          in
           match field with
           | Rtag (label, _, true (*empty*), []) ->
-            Exp.case (pdup (fun _ -> Pat.variant label None)) [%expr true]
+            Exp.case (pdup (fun _ -> variant label None)) [%expr true]
           | Rtag (label, _, false, [typ]) ->
-            Exp.case (pdup (fun var -> Pat.variant label (Some (pvar var))))
+            Exp.case (pdup (fun var -> variant label (Some (pvar var))))
                      (app (expr_of_typ typ) [evar "lhs"; evar "rhs"])
           | Rinherit ({ ptyp_desc = Ptyp_constr (tname, _) } as typ) ->
             Exp.case (pdup (fun var -> Pat.alias (Pat.type_ tname) (mknoloc var)))

src_plugins/ppx_deriving_fold.cppo.ml

@@ -63,11 +63,18 @@ let rec expr_of_typ typ =
   | { ptyp_desc = Ptyp_variant (fields, _, _); ptyp_loc } ->
     let cases =
       fields |> List.map (fun field ->
+        let variant label popt =
+#if OCAML_VERSION < (4, 06, 0)
+          Pat.variant label popt
+#else
+          Pat.variant label.txt popt
+#endif
+        in
         match field with
         | Rtag (label, _, true (*empty*), []) ->
-          Exp.case (Pat.variant label None) [%expr acc]
+          Exp.case (variant label None) [%expr acc]
         | Rtag (label, _, false, [typ]) ->
-          Exp.case (Pat.variant label (Some [%pat? x]))
+          Exp.case (variant label (Some [%pat? x]))
                    [%expr [%e expr_of_typ typ] acc x]
         | Rinherit ({ ptyp_desc = Ptyp_constr (tname, _) } as typ) ->
           Exp.case [%pat? [%p Pat.type_ tname] as x]

src_plugins/ppx_deriving_iter.cppo.ml

@@ -60,11 +60,18 @@ let rec expr_of_typ typ =
   | { ptyp_desc = Ptyp_variant (fields, _, _); ptyp_loc } ->
     let cases =
       fields |> List.map (fun field ->
+        let variant label popt =
+#if OCAML_VERSION < (4, 06, 0)
+          Pat.variant label popt
+#else
+          Pat.variant label.txt popt
+#endif
+        in
         match field with
         | Rtag (label, _, true (*empty*), []) ->
-          Exp.case (Pat.variant label None) [%expr ()]
+          Exp.case (variant label None) [%expr ()]
         | Rtag (label, _, false, [typ]) ->
-          Exp.case (Pat.variant label (Some [%pat? x]))
+          Exp.case (variant label (Some [%pat? x]))
                    [%expr [%e expr_of_typ typ] x]
         | Rinherit ({ ptyp_desc = Ptyp_constr (tname, _) } as typ) ->
           Exp.case [%pat? [%p Pat.type_ tname] as x]

src_plugins/ppx_deriving_map.cppo.ml

@@ -59,12 +59,26 @@ let rec expr_of_typ ?decl typ =
   | { ptyp_desc = Ptyp_variant (fields, _, _); ptyp_loc } ->
     let cases =
       fields |> List.map (fun field ->
+        let pat_variant label popt =
+#if OCAML_VERSION < (4, 06, 0)
+          Pat.variant label popt
+#else
+          Pat.variant label.txt popt
+#endif
+        in
+        let exp_variant label popt =
+#if OCAML_VERSION < (4, 06, 0)
+          Exp.variant label popt
+#else
+          Exp.variant label.txt popt
+#endif
+        in
         match field with
         | Rtag (label, _, true (*empty*), []) ->
-          Exp.case (Pat.variant label None) (Exp.variant label None)
+          Exp.case (pat_variant label None) (exp_variant label None)
         | Rtag (label, _, false, [typ]) ->
-          Exp.case (Pat.variant label (Some [%pat? x]))
-                   (Exp.variant label (Some [%expr [%e expr_of_typ ?decl typ] x]))
+          Exp.case (pat_variant label (Some [%pat? x]))
+                   (exp_variant label (Some [%expr [%e expr_of_typ ?decl typ] x]))
         | Rinherit ({ ptyp_desc = Ptyp_constr (tname, _) } as typ) -> begin
           match decl with
           | None -> 

src_plugins/ppx_deriving_ord.cppo.ml

@@ -127,14 +127,21 @@ and expr_of_typ quoter typ =
       [%expr fun [%p ptuple (pattn `lhs typs)] [%p ptuple (pattn `rhs typs)] ->
         [%e exprn quoter typs |> reduce_compare]]
     | { ptyp_desc = Ptyp_variant (fields, _, _); ptyp_loc } ->
+      let variant label popt =
+#if OCAML_VERSION < (4, 06, 0)
+        Pat.variant label popt
+#else
+        Pat.variant label.txt popt
+#endif
+      in
       let cases =
         fields |> List.map (fun field ->
           let pdup f = ptuple [f "lhs"; f "rhs"] in
           match field with
           | Rtag (label, _, true (*empty*), []) ->
-            Exp.case (pdup (fun _ -> Pat.variant label None)) [%expr 0]
+            Exp.case (pdup (fun _ -> variant label None)) [%expr 0]
           | Rtag (label, _, false, [typ]) ->
-            Exp.case (pdup (fun var -> Pat.variant label (Some (pvar var))))
+            Exp.case (pdup (fun var -> variant label (Some (pvar var))))
                      (app (expr_of_typ typ) [evar "lhs"; evar "rhs"])
           | Rinherit ({ ptyp_desc = Ptyp_constr (tname, _) } as typ) ->
             Exp.case (pdup (fun var -> Pat.alias (Pat.type_ tname) (mknoloc var)))
@@ -147,9 +154,9 @@ and expr_of_typ quoter typ =
         fields |> List.mapi (fun i field ->
           match field with
           | Rtag (label, _, true (*empty*), []) ->
-            Exp.case (Pat.variant label None) (int i)
+            Exp.case (variant label None) (int i)
           | Rtag (label, _, false, [typ]) ->
-            Exp.case (Pat.variant label (Some [%pat? _])) (int i)
+            Exp.case (variant label (Some [%pat? _])) (int i)
           | Rinherit { ptyp_desc = Ptyp_constr (tname, []) } ->
             Exp.case (Pat.type_ tname) (int i)
           | _ -> assert false)

src_plugins/ppx_deriving_show.cppo.ml

@@ -166,9 +166,15 @@ let rec expr_of_typ quoter typ =
         fields |> List.map (fun field ->
           match field with
           | Rtag (label, _, true (*empty*), []) ->
+#if OCAML_VERSION >= (4, 06, 0)
+            let label = label.txt in
+#endif
             Exp.case (Pat.variant label None)
                      [%expr Format.pp_print_string fmt [%e str ("`" ^ label)]]
           | Rtag (label, _, false, [typ]) ->
+#if OCAML_VERSION >= (4, 06, 0)
+            let label = label.txt in
+#endif
             Exp.case (Pat.variant label (Some [%pat? x]))
                      [%expr Format.fprintf fmt [%e str ("`" ^ label ^ " (@[<hov>")];
                             [%e expr_of_typ typ] x;