diff -r 9c51a5de76db -r 98976e3cae57 mercurial/scmutil.py
--- a/mercurial/scmutil.py	Sat Aug 06 20:37:48 2016 +0900
+++ b/mercurial/scmutil.py	Sat Aug 06 20:46:53 2016 +0900
@@ -781,7 +781,6 @@
 
 def _pairspec(revspec):
     tree = revset.parse(revspec)
-    tree = revset.optimize(tree)  # fix up "x^:y" -> "(x^):y"
     return tree and tree[0] in ('range', 'rangepre', 'rangepost', 'rangeall')
 
 def revpair(repo, revs):