c++: wrong pretty printing of nested type [PR95303]

c++: wrong pretty printing of nested type [PR95303]

In the testcase below, we pretty print the nested type A<int>::B as
A<int>::B<int> because we don't check whether B is itself a class
template before printing the innermost set of template arguments from
B's TEMPLATE_INFO (which in this case belong to A).  This patch fixes
this by checking PRIMARY_TEMPLATE_P beforehand.

gcc/cp/ChangeLog:

	PR c++/95303
	* cxx-pretty-print.c (pp_cxx_unqualified_id): Check
	PRIMARY_TEMPLATE_P before printing the innermost template
	arguments.

gcc/testsuite/ChangeLog:

	PR c++/95303
	* g++.dg/concepts/diagnostic14.C: New test.