PR c++/46977

	PR c++/46977
	* semantics.c (potential_constant_expression_1): Split out from
	potential_constant_expression.  Add want_rval parm.  Handle
	template expression forms.  Don't enforce restriction on address
	of automatic variable here.  Add a couple of diagnostics that
	had been missing.
	(require_potential_constant_expression): New entry point.
	(build_data_member_initialization, register_constexpr_fundef): Adjust.
	(maybe_constant_value): Check potential_constant_expression.
	* pt.c (fold_non_dependent_expr_sfinae): Likewise.
	* tree.c (build_vec_init_expr): Adjust.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@169096 138bc75d-0d04-0410-961f-82ee72b054a4