c++: using-enum and access specifiers [PR100862]

c++: using-enum and access specifiers [PR100862]

When copying the enumerators imported by a class-scope using-enum
declaration, we need to override current_access_specifier so that
finish_member_declaration gives the copies the same access as the
using-enum decl.  (A class-scope using-enum is processed late, so
current_access_specifier at this point is otherwise set to the last
access specifier within the class.)  To that end, this patch makes
handle_using_decl call set_current_access_from_decl accordingly.

For consistency, this patch makes build_enumerator use
set_current_access_from_decl too.

	PR c++/100862

gcc/cp/ChangeLog:

	* pt.c (set_current_access_from_decl): Move to ...
	* class.c (set_current_access_from_decl): ... here.
	(handle_using_decl): Use it to propagate the access of the
	using-enum decl to the copy of the imported enumerator.
	* cp-tree.h (set_current_access_from_decl): Declare.
	* decl.c (build_enumerator): Simplify using make_temp_override
	and set_current_access_from_decl.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/using-enum-9.C: New test.