PR c++/83993
	* constexpr.c (diag_array_subscript): Emit different diagnostics
	if TYPE_DOMAIN (arraytype) is NULL.
	(cxx_eval_array_reference, cxx_eval_store_expression): For arrays
	with NULL TYPE_DOMAIN use size_zero_node as nelts.

	* g++.dg/init/pr83993-1.C: New test.
	* g++.dg/cpp0x/pr83993.C: New test.

From-SVN: r257264