should be union; we want to exclude dangling refs

1 year ago · a07446808a
parent 340fe7f656
commit a07446808a
1 changed files with 1 additions and 1 deletions
--- a/masque/library.py
+++ b/masque/library.py
@ -781,7 +781,7 @@ class MutableLibrary(Library, MutableMapping[str, 'Pattern'], metaclass=ABCMeta)
        keep |= set(tops)
        new = type(self)()
-        for key in keep - set(self.keys()):
+        for key in keep & set(self.keys()):
            new._merge(key, self, key)
        return new