2017-07-14  Jason Merrill  <jason@redhat.com>
	    Jonathan Wakely  <jwakely@redhat.com>

	* include/std/variant (variant::variant(_Tp&&)): Constrain to remove
	the constructor for empty variants from the candidate functions
	during class template argument deduction.
	* testsuite/20_util/variant/deduction.cc: New.

Co-Authored-By: Jonathan Wakely <jwakely@redhat.com>

From-SVN: r250213