c++/modules: imported spec befriending class tmpl [PR114889]

When adding to CLASSTYPE_BEFRIENDING_CLASSES as part of installing an
imported class definition, we need to look through TEMPLATE_DECL like
make_friend_class does.

Otherwise in the below testcase we won't add _Hashtable<int, int> to
CLASSTYPE_BEFRIENDING_CLASSES of _Map_base, which leads to a bogus
access check failure for _M_hash_code.

	PR c++/114889

gcc/cp/ChangeLog:

	* module.cc (trees_in::read_class_def): Look through
	TEMPLATE_DECL when adding to CLASSTYPE_BEFRIENDING_CLASSES.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/friend-8_a.H: New test.
	* g++.dg/modules/friend-8_b.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>

gcc/cp/module.cc

@@ -12498,6 +12498,8 @@ trees_in::read_class_def (tree defn, tree maybe_template)
 	  for (; friend_classes; friend_classes = TREE_CHAIN (friend_classes))
 	    {
 	      tree f = TREE_VALUE (friend_classes);
+	      if (TREE_CODE (f) == TEMPLATE_DECL)
+		f = TREE_TYPE (f);
 
 	      if (CLASS_TYPE_P (f))
 		{

gcc/testsuite/g++.dg/modules/friend-8_a.H

@@ -0,0 +1,23 @@
+// PR c++/114889
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+template<class, class>
+struct _Hashtable;
+
+template<class _Key, class _Val>
+struct _Map_base {
+  void f() {
+    _Hashtable<_Key, _Val> __h;
+    __h._M_hash_code(0);
+  }
+};
+
+template<class _Key, class _Value>
+struct _Hashtable {
+  template<class, class> friend struct _Map_base;
+protected:
+  void _M_hash_code(int);
+};
+
+inline _Hashtable<int, int> m;

gcc/testsuite/g++.dg/modules/friend-8_b.C

@@ -0,0 +1,9 @@
+// PR c++/114889
+// { dg-additional-options "-fmodules-ts" }
+
+import "friend-8_a.H";
+
+int main() {
+  _Map_base<int, int> m;
+  m.f();
+}