c++: Note duplicates in symbol table [PR 99283]

I ran into this reducing 99283, we were failing to mark binding
vectors when the current TU declares a duplicate decl (as opposed to
an import introduces a duplicate).

	PR c++/99283
	gcc/cp/
	* name-lookup.c (check_module_override): Set global or partition
	DUP on the binding vector.
	gcc/testsuite/
	* g++.dg/modules/pr99283-1_a.H: New.
	* g++.dg/modules/pr99283-1_b.H: New.

gcc/cp/name-lookup.c

@@ -3528,6 +3528,7 @@ static tree
 check_module_override (tree decl, tree mvec, bool hiding,
 		       tree scope, tree name)
 {
+  tree match = NULL_TREE;
   bitmap imports = get_import_bitmap ();
   binding_cluster *cluster = BINDING_VECTOR_CLUSTER_BASE (mvec);
   unsigned ix = BINDING_VECTOR_NUM_CLUSTERS (mvec);
@@ -3566,13 +3567,15 @@ check_module_override (tree decl, tree mvec, bool hiding,
 	  bind = STAT_VISIBLE (bind);
 
 	for (ovl_iterator iter (bind); iter; ++iter)
-	  if (iter.using_p ())
-	    ;
-	  else if (tree match = duplicate_decls (decl, *iter, hiding))
-	    return match;
+	  if (!iter.using_p ())
+	    {
+	      match = duplicate_decls (decl, *iter, hiding);
+	      if (match)
+		goto matched;
+	    }
       }
 
-  if (TREE_PUBLIC (scope) && TREE_PUBLIC (decl) && !not_module_p ()
+  if (TREE_PUBLIC (scope) && TREE_PUBLIC (STRIP_TEMPLATE (decl))
       /* Namespaces are dealt with specially in
 	 make_namespace_finish.  */
       && !(TREE_CODE (decl) == NAMESPACE_DECL && !DECL_NAMESPACE_ALIAS (decl)))
@@ -3588,14 +3591,26 @@ check_module_override (tree decl, tree mvec, bool hiding,
 
       for (ovl_iterator iter (mergeable); iter; ++iter)
 	{
-	  tree match = *iter;
-	  
-	  if (duplicate_decls (decl, match, hiding))
-	    return match;
+	  match = duplicate_decls (decl, *iter, hiding);
+	  if (match)
+	    goto matched;
 	}
     }
 
   return NULL_TREE;
+
+ matched:
+  if (match != error_mark_node)
+    {
+      if (named_module_p ())
+	BINDING_VECTOR_PARTITION_DUPS_P (mvec) = true;
+      else
+	BINDING_VECTOR_GLOBAL_DUPS_P (mvec) = true;
+    }
+
+  return match;
+
+  
 }
 
 /* Record DECL as belonging to the current lexical scope.  Check for

gcc/testsuite/g++.dg/modules/pr99283-1_a.H

@@ -0,0 +1,6 @@
+// PR 99283 part 1 ICE on specialization
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+template<typename _Facet>
+_Facet &use_facet ();

gcc/testsuite/g++.dg/modules/pr99283-1_b.H

@@ -0,0 +1,10 @@
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+import  "pr99283-1_a.H";
+
+template<typename _Facet>
+_Facet &use_facet ();
+
+extern template
+char &use_facet<char> ();