move typeChecked into pkgs.liminix.lib

pkgs/default.nix

@@ -1,5 +1,6 @@
 {
   callPackage
+, lib
 }:
 {
   pseudofile = callPackage ./pseudofile {};
@@ -10,6 +11,23 @@
       squashfs = callPackage ./liminix-tools/builders/squashfs.nix {};
       kernel = callPackage ./kernel {};
     };
+    lib = {
+      types = {
+        service =
+          let inherit (lib) types isDerivation hasAttr;
+          in types.package // {
+            name = "service";
+            description = "s6-rc service";
+            check = x: isDerivation x && hasAttr "serviceType" x;
+          };
+      };
+      typeChecked = caller: type: value:
+        let
+          inherit (lib) types mergeDefinitions;
+          defs = [{ file = caller; inherit value; }];
+          type' = types.submodule { options = type; };
+        in (mergeDefinitions [] type' defs).mergedValue;
+    };
   };
   writeFennelScript = callPackage ./write-fennel-script {};
   writeAshScript = callPackage ./write-ash-script {};

pkgs/liminix-tools/networking/pppoe.nix

@@ -8,26 +8,23 @@
 } :
 let
   inherit (liminix.services) longrun;
+  inherit (liminix.lib) typeChecked;
   inherit (lib)
     mergeDefinitions
     mkEnableOption mkOption isType types isDerivation hasAttr;
   t = {
     interface = mkOption {
-      type = types.package;     # actually a service
+      type = liminix.lib.types.service;
       description = "ethernet interface to run PPPoE over";
     };
     ppp-options = mkOption {
       type = types.listOf types.str;
     };
   };
-  t' = types.submodule { options = t; };
-  typeChecked = type: value:
-    let defs = [{ file = "pppoe.nix"; inherit value; }];
-    in (lib.mergeDefinitions [ ] type defs).mergedValue;
 in
 params:
 let
-  inherit (typeChecked t' params) ppp-options interface;
+  inherit (typeChecked "pppoe.nix" t params) ppp-options interface;
   name = "${interface.device}.pppoe";
   ip-up = writeAshScript "ip-up" {} ''
     . ${serviceFns}