eval.nix: Auto-call functors as well

This makes some very cursed setup work :P

src/nix/hive/eval.nix

@@ -268,7 +268,7 @@ let
     in hive;
 
     rawToHive = rawHive:
-      if typeOf rawHive == "lambda" then rawHive {}
+      if typeOf rawHive == "lambda" || rawHive ? __functor then rawHive {}
       else if typeOf rawHive == "set" then rawHive
       else throw "The config must evaluate to an attribute set.";
   in

src/nix/tests/mod.rs

@@ -427,6 +427,17 @@ fn test_hive_autocall() {
       }
     "#);
 
+    TempHive::valid(r#"
+      {
+        some = "value";
+        __functor = self: { argument ? "with default value" }: {
+          borg = { ... }: {
+            boot.isContainer = assert self.some == "value"; true;
+          };
+        };
+      }
+    "#);
+
     TempHive::invalid(r#"
       {
         thisWontWork