2015-10-20 Ed Schonberg <schonberg@adacore.com>

2015-10-20  Ed Schonberg  <schonberg@adacore.com>

	* sem_ch3.adb (Check_Nonoverridable_Aspects): New procedure within
	Analyze_Full_Type_ Declaration, used to apply legality rules in
	13,1,1 (18.3.3) concerning aspects that cannot be overridden in
	a type extension.
	(Check_Duplicate_Aspects): It is not legal to specify the
	Implicit_Dereference aspect on a full view if partial view has
	known discriminants.
	* sem_ch13.adb (Analyze_Aspect_Implicit_Dereference): Verify that
	the specification of the aspect on a derived type confirms the
	value of the inherited one.
	* sem_util.adb (Reference_Discriminant): Return empty if none
	specified.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@229026 138bc75d-0d04-0410-961f-82ee72b054a4