c++: Don't ICE to build private access error message [PR116323]

We currently ICE upon the following code while building the "[...] is
private within this context" error message

=== cut here ===
class A { enum Enum{}; };
template<typename E, template<typename> class Alloc>
class B : private Alloc<E>, private A {};
template<typename E, template<typename> class Alloc>
int B<E, Alloc>::foo (Enum m) { return 42; }
=== cut here ===

The problem is that since r11-6880, after detecting that Enum cannot be
accessed in B, enforce_access will access the TYPE_BINFO of all the
bases of B, which ICEs for any that is a BOUND_TEMPLATE_TEMPLATE_PARM.
This patch simply skips such bases.

	PR c++/116323

gcc/cp/ChangeLog:

	* search.cc (get_parent_with_private_access): Only call access_in_type
	for RECORD_OR_UNION_TYPE_P base BINFOs.

gcc/testsuite/ChangeLog:

	* g++.dg/template/access43.C: New test.

gcc/cp/search.cc

@@ -160,12 +160,16 @@ get_parent_with_private_access (tree decl, tree binfo)
 
   tree base_binfo = NULL_TREE;
 
-  /* Iterate through immediate parent classes.  */
+  /* Iterate through immediate parent classes.
+     Note that the base list might contain WILDCARD_TYPE_P types, that
+     should be ignored here.  */
   for (int i = 0; BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
     {
+      tree base_binfo_type = BINFO_TYPE (base_binfo);
       /* This parent had private access.  Therefore that's why BINFO can't
 	  access DECL.  */
-      if (access_in_type (BINFO_TYPE (base_binfo), decl) == ak_private)
+      if (RECORD_OR_UNION_TYPE_P (base_binfo_type)
+	  && access_in_type (base_binfo_type, decl) == ak_private)
 	return base_binfo;
     }
 

gcc/testsuite/g++.dg/template/access43.C

@@ -0,0 +1,11 @@
+// PR c++/116323
+// { dg-do "compile" }
+// { dg-additional-options "-Wno-template-body" }
+
+class A { enum Enum{}; };
+
+template<typename E, template<typename> class Alloc>
+class B : private Alloc<E>, private A {};
+
+template<typename E, template<typename> class Alloc>
+int B<E, Alloc>::foo (Enum m) { return 42; } // { dg-error "is private" }