diff -r b837655c1509 -r d7f3fdab94c4 mercurial/context.py
--- a/mercurial/context.py	Wed Jan 31 17:15:44 2018 +0100
+++ b/mercurial/context.py	Thu Mar 29 21:15:40 2018 -0700
@@ -66,13 +66,7 @@
         if isinstance(changeid, basectx):
             return changeid
 
-        o = super(basectx, cls).__new__(cls)
-
-        o._repo = repo
-        o._rev = nullrev
-        o._node = nullid
-
-        return o
+        return super(basectx, cls).__new__(cls)
 
     def __bytes__(self):
         return short(self.node())