* Add a type "path".

svn path=/nixpkgs/trunk/; revision=34247

pkgs/lib/types.nix

@@ -64,7 +64,7 @@ rec {
 
     string = mkOptionType {
       name = "string";
-      check = lib.traceValIfNot (x: builtins ? isString -> builtins.isString x);
+      check = lib.traceValIfNot builtins.isString;
       merge = lib.concatStrings;
     };
 
@@ -86,6 +86,12 @@ rec {
       check = lib.traceValIfNot isDerivation;
     };
 
+    path = mkOptionType {
+      name = "path";
+      # Hacky: there is no ‘isPath’ primop.
+      check = lib.traceValIfNot (x: builtins.substring 0 1 (toString x) == "/");
+    };
+
     listOf = types.list;
     list = elemType: mkOptionType {
       name = "list of ${elemType.name}s";