warn if reserved inputs provided

nix/snow/flake/default.nix

@@ -4,23 +4,55 @@
   systems,
   ...
 }: let
+  inherit
+    (builtins)
+    attrNames
+    concatStringsSep
+    filter
+    length
+    removeAttrs
+    warn
+    ;
+
   inherit (inputs.nixpkgs) lib;
 in {
   # snow.flake
   flake = flakeInputs: root: let
     snowflake = lib.evalModules {
       class = "snowflake";
-      # XXX: TODO: abort if inputs contains reserved names
-      specialArgs =
-        (flakeInputs
-          // {
-            inherit (this) snow;
-            inherit systems root;
-            inputs = flakeInputs;
-          })
-        # XXX: TODO:
-        # |> (x: builtins.removeAttrs x ["self" "nodes"]);
-        |> (x: builtins.removeAttrs x ["self"]);
+      specialArgs = let
+        reservedInputs = {
+          inherit (this) snow;
+          inherit systems root;
+          inputs = flakeInputs;
+        };
+
+        warnIfReserved = let
+          getReservedNames = names:
+            reservedInputs
+            |> attrNames
+            |> filter (name: names?${name});
+
+          reservedNames =
+            flakeInputs
+            |> attrNames
+            |> getReservedNames;
+        in
+          (length reservedNames == 0)
+          || warn ''
+            [snow] Your `flake.nix` declares inputs using reserved names!
+            [snow] These will be accessible only via `inputs.''${NAME}`
+            [snow] Please rename the following:
+            [snow]   ${concatStringsSep reservedNames ", "}
+          ''
+          true;
+      in
+        assert warnIfReserved;
+          flakeInputs
+          // reservedInputs
+          # XXX: TODO:
+          # |> (x: builtins.removeAttrs x ["self" "nodes"]);
+          |> (x: removeAttrs x ["self"]);
 
       modules = [
         ./module.nix