diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -875,6 +875,8 @@
         if common is None:
             common = [nullrev]
 
+        if rustext is not None:
+            return rustext.ancestor.MissingAncestors(self.index, common)
         return ancestor.incrementalmissingancestors(self.parentrevs, common)
 
     def findmissingrevs(self, common=None, heads=None):
diff --git a/mercurial/setdiscovery.py b/mercurial/setdiscovery.py
--- a/mercurial/setdiscovery.py
+++ b/mercurial/setdiscovery.py
@@ -186,9 +186,15 @@
         """the heads of the known common set"""
         # heads(common) == heads(common.bases) since common represents
         # common.bases and all its ancestors
+        bases = self._common.bases
+        if callable(bases):
+            # This happens for Rust exported object, and we don't know
+            # at the moment how to make an equivalent of property for them
+            bases = bases()
+
         # The presence of nullrev will confuse heads(). So filter it out.
         return set(self._repo.revs('heads(%ld)',
-                   self._common.bases - {nullrev}))
+                                   (r for r in bases if r != nullrev)))
 
 def findcommonheads(ui, local, remote,
                     initialsamplesize=100,