Add the tool "nixos-typecheck" that can check an option declaration to:

 - Enforce that an option declaration has a "defaultText" if and only if the
   type of the option derives from "package", "packageSet" or "nixpkgsConfig"
   and if a "default" attribute is defined.

 - Enforce that the value of the "example" attribute is wrapped with "literalExample"
   if the type of the option derives from "package", "packageSet" or "nixpkgsConfig".

 - Warn if a "defaultText" is defined in an option declaration if the type of
   the option does not derive from "package", "packageSet" or "nixpkgsConfig".

 - Warn if no "type" is defined in an option declaration.

1 files changed, 4 insertions, 0 deletions

diff --git a/nixos/modules/services/misc/ihaskell.nix b/nixos/modules/services/misc/ihaskell.nix
index d0e9b839e754..c177d68c8fe0 100644
--- a/nixos/modules/services/misc/ihaskell.nix
+++ b/nixos/modules/services/misc/ihaskell.nix
@@ -15,12 +15,14 @@ in
   options = {
     services.ihaskell = {
       enable = mkOption {
+        type = lib.types.bool;
         default = false;
         example = true;
         description = "Autostart an IHaskell notebook service.";
       };
 
       haskellPackages = mkOption {
+        type = lib.types.packageSet;
         default = pkgs.haskellPackages;
         defaultText = "pkgs.haskellPackages";
         example = literalExample "pkgs.haskell.packages.ghc784";
@@ -33,7 +35,9 @@ in
       };
 
       extraPackages = mkOption {
+        type = types.functionTo (types.listOf types.package);
         default = self: [];
+        defaultText = "self: []";
         example = literalExample ''
           haskellPackages: [
             haskellPackages.wreq