c++: instantiating imported specializations [PR 99389]

When an incomplete class specialization is imported, and is completed
by instantiation, we were failing to mark the instantiation, and thus
didn't stream it out.  Leading to errors in importing as we had
members of an incomplete type.

	PR c++/99389
	gcc/cp/
	* pt.c (instantiate_class_template_1): Set instantiating module
	here.
	gcc/testsuite/
	* g++.dg/modules/pr99389_a.H: New.
	* g++.dg/modules/pr99389_b.C: New.
	* g++.dg/modules/pr99389_c.C: New.

gcc/cp/pt.c

@@ -11816,6 +11816,8 @@ instantiate_class_template_1 (tree type)
   input_location = DECL_SOURCE_LOCATION (TYPE_NAME (type)) =
     DECL_SOURCE_LOCATION (typedecl);
 
+  set_instantiating_module (TYPE_NAME (type));
+
   TYPE_PACKED (type) = TYPE_PACKED (pattern);
   SET_TYPE_ALIGN (type, TYPE_ALIGN (pattern));
   TYPE_USER_ALIGN (type) = TYPE_USER_ALIGN (pattern);

gcc/testsuite/g++.dg/modules/pr99389_a.H

@@ -0,0 +1,20 @@
+// PR 99389 failed to stream class specialization
+// { dg-module-do link }
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+template<typename _CharT>
+class basic_string_view
+{
+public:
+  basic_string_view(const _CharT* __str) noexcept
+  {}
+  bool
+    empty() const noexcept
+  { return !_M_len; }
+  
+private:
+  unsigned _M_len;
+};
+
+using string_view = basic_string_view<char>;
+

gcc/testsuite/g++.dg/modules/pr99389_b.C

@@ -0,0 +1,12 @@
+// { dg-additional-options {-fmodules-ts -fdump-lang-module } }
+export module hello;
+// { dg-module-cmi hello }
+
+import "pr99389_a.H";
+
+export inline bool Check (const string_view& n)
+{
+  return !n.empty ();
+}
+
+// { dg-final { scan-lang-dump {Pending specialization '::basic_string_view<char>' entity:. section:. keyed to '::basic_string_view'} module } }

gcc/testsuite/g++.dg/modules/pr99389_c.C

@@ -0,0 +1,7 @@
+// { dg-additional-options -fmodules-ts }
+import hello;
+
+int main ()
+{
+  return Check ("World") ? 0 : 1;
+}