fatal/container/flag_set.h: avoid a newly-exposed -Wint-in-bool-conte…

…xt warning

Summary:
This avoids the following errors:

  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<>::flags_type(1) << try_index_of<tag_list, x<0> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<>::flags_type(1) << try_index_of<tag_list, x<1> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<>::flags_type(1) << try_index_of<tag_list, x<2> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<>::flags_type(1) << try_index_of<tag_list, x<3> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<>::flags_type(1) << try_index_of<tag_list, x<4> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<>::flags_type(1) << try_index_of<tag_list, x<5> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<fatal::x<0> >::flags_type(1) << try_index_of<tag_list, x<0> >::value) != 0'? [-Werror,-Wint-in-bool-context]
  fatal/container/flag_set.h:80:26: error: converting the result of '<<' to a boolean; did you mean '(fatal::flag_set<fatal::x<1> >::flags_type(1) << try_index_of<tag_list, x<1> >::value) != 0'? [-Werror,-Wint-in-bool-context]

Reviewed By: igorsugak

Differential Revision: D33337831

fbshipit-source-id: ce9304c960abbafe348c61d47fbb265ae9c2d2d7

fatal/container/flag_set.h

@@ -77,7 +77,7 @@ struct flag_set {
         flags_type
       >::type,
       (try_index_of<tag_list, UFlags>::value < size<tag_list>::value
-        ? (flags_type(1) << try_index_of<tag_list, UFlags>::value)
+        ? ((flags_type(1) << try_index_of<tag_list, UFlags>::value) != 0)
         : 0
       )
     >...