diff -r 53e6b7e05553 -r 0023da2910c9 mercurial/templateutil.py
--- a/mercurial/templateutil.py	Fri Mar 23 20:23:55 2018 +0900
+++ b/mercurial/templateutil.py	Fri Mar 23 21:03:21 2018 +0900
@@ -287,7 +287,12 @@
 
 def evalfuncarg(context, mapping, arg):
     """Evaluate given argument as value type"""
-    thing = evalrawexp(context, mapping, arg)
+    return _unwrapvalue(evalrawexp(context, mapping, arg))
+
+# TODO: unify this with unwrapvalue() once the bug of templatefunc.join()
+# is fixed. we can't do that right now because join() has to take a generator
+# of byte strings as it is, not a lazy byte string.
+def _unwrapvalue(thing):
     thing = unwrapvalue(thing)
     # evalrawexp() may return string, generator of strings or arbitrary object
     # such as date tuple, but filter does not want generator.