Merge options having the submodule type.

Now we should be able to have multiple declaration of the same option as
long as all declarations have the same type.  If the type has a sub module,
then it is merged with the submodules of other declarations, as done with
option sets.

In addition, the file of the option declaration is passed into the
submodule, such as the documentation can display it correctly.

lib/types.nix

@@ -33,9 +33,14 @@ rec {
     , # Return a flat list of sub-options.  Used to generate
       # documentation.
       getSubOptions ? prefix: {}
+    , # List of modules if any, or null if none.
+      getSubModules ? null
+    , # Function for building the same option type  with a different list of
+      # modules.
+      substSubModules ? m: null
     }:
     { _type = "option-type";
-      inherit name check merge getSubOptions;
+      inherit name check merge getSubOptions getSubModules substSubModules;
     };
 
 
@@ -110,6 +115,8 @@ rec {
           elemType.merge (loc ++ ["[${toString n}-${toString m}]"])
             [{ inherit (def) file; value = def'; }]) def.value) defs);
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["*"]);
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: listOf (elemType.substSubModules m);
     };
 
     attrsOf = elemType: mkOptionType {
@@ -121,6 +128,8 @@ rec {
           (map (def: listToAttrs (mapAttrsToList (n: def':
             { name = n; value = { inherit (def) file; value = def'; }; }) def.value)) defs);
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["<name>"]);
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: attrsOf (elemType.substSubModules m);
     };
 
     # List or attribute set of ...
@@ -147,12 +156,16 @@ rec {
           else false;
         merge = loc: defs: attrOnly.merge loc (imap convertIfList defs);
         getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["<name?>"]);
+        getSubModules = elemType.getSubModules;
+        substSubModules = m: loaOf (elemType.substSubModules m);
       };
 
     uniq = elemType: mkOptionType {
       inherit (elemType) name check;
       merge = mergeOneOption;
       getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: uniq (elemType.substSubModules m);
     };
 
     nullOr = elemType: mkOptionType {
@@ -165,6 +178,8 @@ rec {
           throw "The option `${showOption loc}' is defined both null and not null, in ${showFiles (getFiles defs)}."
         else elemType.merge loc defs;
       getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: nullOr (elemType.substSubModules m);
     };
 
     functionTo = elemType: mkOptionType {
@@ -173,6 +188,8 @@ rec {
       merge = loc: defs:
         fnArgs: elemType.merge loc (map (fn: { inherit (fn) file; value = fn.value fnArgs; }) defs);
       getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: functionTo (elemType.substSubModules m);
     };
 
     submodule = opts:
@@ -192,6 +209,8 @@ rec {
           { modules = opts'; inherit prefix;
             # FIXME: hack to get shit to evaluate.
             args = { name = ""; }; }).options;
+        getSubModules = opts';
+        substSubModules = m: submodule m;
       };
 
     enum = values: mkOptionType {