--- a/mercurial/templater.py	Thu Jul 26 11:38:13 2012 +0100
+++ b/mercurial/templater.py	Mon Nov 03 12:08:03 2014 -0500
@@ -153,8 +153,6 @@
         return v(**mapping)
     if isinstance(v, types.GeneratorType):
         v = list(v)
-        mapping[key] = v
-        return v
     return v
 
 def buildfilter(exp, context):