diff -r 470ea34ba593 -r a8afdc5a7885 mercurial/fileset.py
--- a/mercurial/fileset.py	Mon Dec 21 22:31:16 2015 +0900
+++ b/mercurial/fileset.py	Mon Dec 21 22:31:16 2015 +0900
@@ -138,10 +138,10 @@
 symbols = {}
 
 # filesets using matchctx.status()
-_statuscallers = []
+_statuscallers = set()
 
 # filesets using matchctx.existing()
-_existingcallers = []
+_existingcallers = set()
 
 def predicate(decl, callstatus=False, callexisting=False):
     """Return a decorator for fileset predicate function
@@ -164,9 +164,9 @@
             name = decl
         symbols[name] = func
         if callstatus:
-            _statuscallers.append(name)
+            _statuscallers.add(name)
         if callexisting:
-            _existingcallers.append(name)
+            _existingcallers.add(name)
         if func.__doc__:
             func.__doc__ = "``%s``\n    %s" % (decl, func.__doc__.strip())
         return func