PR libstdc++/84769 qualify call to std::get<0>

	PR libstdc++/84769
	* include/std/variant (visit): Qualify std::get call.

From-SVN: r259902

libstdc++-v3/ChangeLog

 2018-05-03  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/84769
+	* include/std/variant (visit): Qualify std::get call.
+
 	PR libstdc++/85632 use uintmax_t for arithmetic
 	* src/filesystem/ops.cc (experimental::filesystem::space): Perform
 	arithmetic in result type.

libstdc++-v3/include/std/variant

@@ -1389,7 +1389,7 @@ namespace __variant
 
       using _Result_type =
 	decltype(std::forward<_Visitor>(__visitor)(
-	    get<0>(std::forward<_Variants>(__variants))...));
+	    std::get<0>(std::forward<_Variants>(__variants))...));
 
       constexpr auto& __vtable = __detail::__variant::__gen_vtable<
 	_Result_type, _Visitor&&, _Variants&&...>::_S_vtable;