diff -r 6d21737c35bf -r e18119b1ad5d mercurial/revsetlang.py
--- a/mercurial/revsetlang.py	Sun Sep 03 15:01:23 2017 +0900
+++ b/mercurial/revsetlang.py	Sun Sep 03 17:03:23 2017 +0900
@@ -473,7 +473,7 @@
 
 # the set of valid characters for the initial letter of symbols in
 # alias declarations and definitions
-_aliassyminitletters = _syminitletters | set(pycompat.sysstr('$'))
+_aliassyminitletters = _syminitletters | {'$'}
 
 def _parsewith(spec, lookup=None, syminitletters=None):
     """Generate a parse tree of given spec with given tokenizing options