1 files changed, 11 insertions, 0 deletions
diff --git a/nixpkgs/lib/types.nix b/nixpkgs/lib/types.nix
index ee891f8231b6..d0a8e96149d7 100644
--- a/nixpkgs/lib/types.nix
+++ b/nixpkgs/lib/types.nix
@@ -453,6 +453,17 @@ rec {
       functor = (defaultFunctor name) // { wrapped = elemType; };
     };
 
+    functionTo = elemType: mkOptionType {
+      name = "functionTo";
+      description = "function that evaluates to a(n) ${elemType.name}";
+      check = isFunction;
+      merge = loc: defs:
+        fnArgs: (mergeDefinitions (loc ++ [ "[function body]" ]) elemType (map (fn: { inherit (fn) file; value = fn.value fnArgs; }) defs)).mergedValue;
+      getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: functionTo (elemType.substSubModules m);
+    };
+
     # A submodule (like typed attribute set). See NixOS manual.
     submodule = modules: submoduleWith {
       shorthandOnlyDefinesConfig = true;