fix oversight in struct cmp/merge implementation

nib/parse/struct.nix

@@ -48,12 +48,23 @@
         inherit path;
       });
 
+  cmpTypedPartialStruct =
+    cmpStructErr
+    (path: keysS: keysT:
+      result.Ok "ok")
+    (path: S: T:
+      result.Err {
+        reason = "values";
+        inherit path;
+      });
+
   # check is a function taking two structs
   # and returning a result monad.
   mergeStruct' = check: template: S: let
     res = check template S;
   in
     result.errOr res ({...}:
+      result.Ok (
         attrs.mapAttrsRecursive (
           path: value: let
             valueS = attrs.attrValueAt S path;
@@ -62,22 +73,13 @@
             then valueS
             else value
         )
-      template);
+        template
+      ));
 
+  # mergeStruct ensures no properties are evaluated (entirely lazy)
   mergeStruct = mergeStruct' (S: T: result.Ok "ok");
 
-  mergeTypedStruct = mergeStruct' (
-    cmpStructErr
-    (path: keysS: keysT:
-      result.Ok "ok")
-    (path: S: T:
-      result.Err {
-        reason = "values";
-        inherit path;
-      })
-  );
-
-  mergeStructStrict = mergeStruct' cmpStruct;
-
-  mergeTypedStructStrict = mergeStruct' cmpTypedStruct;
+  # mergeTypedPartialStruct must evaluate properties (not lazy)
+  # for lazy evaluation use mergeStruct instead!
+  mergeTypedPartialStruct = mergeStruct' cmpTypedPartialStruct;
 }