1 files changed, 52 insertions, 33 deletions

diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index b753061..4c07fd4 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -1338,6 +1338,7 @@ name_lookup::adl_namespace_fns (tree scope, bitmap imports,
 		      bind = STAT_VISIBLE (bind);
 		  }
 
+		bind = ovl_skip_hidden (bind);
 		if (on_inst_path || visible)
 		  add_fns (bind);
 		else
@@ -1372,11 +1373,14 @@ name_lookup::adl_class_fns (tree type)
 	  {
 	    tree fn = TREE_VALUE (friends);
 
-	    /* Only interested in global functions with potentially hidden
-	       (i.e. unqualified) declarations.  */
+	    /* Before C++20, ADL just makes hidden friends visible, so we
+	       only include functions in the same namespace.  After C++20,
+	       include all namespace-scope functions.  */
 	    if (!context)
 	      context = decl_namespace_context (type);
-	    if (CP_DECL_CONTEXT (fn) != context)
+	    if (cxx_dialect < cxx20
+		? CP_DECL_CONTEXT (fn) != context
+		: !DECL_NAMESPACE_SCOPE_P (fn))
 	      continue;
 
 	    dedup (true);
@@ -4063,6 +4067,11 @@ pushdecl (tree decl, bool hiding)
 	      }
 	}
 
+      /* Skip a hidden builtin we failed to match already.  There can
+	 only be one.  */
+      if (old && anticipated_builtin_p (old))
+	old = OVL_CHAIN (old);
+
       /* Check for redeclaring an import.  */
       if (slot && *slot && TREE_CODE (*slot) == BINDING_VECTOR)
 	if (tree match
@@ -4081,11 +4090,6 @@ pushdecl (tree decl, bool hiding)
 
       /* We are pushing a new decl.  */
 
-      /* Skip a hidden builtin we failed to match already.  There can
-	 only be one.  */
-      if (old && anticipated_builtin_p (old))
-	old = OVL_CHAIN (old);
-
       if (hiding)
 	; /* Hidden bindings don't shadow anything.  */
       else
@@ -5400,7 +5404,11 @@ do_nonmember_using_decl (name_lookup &lookup, bool fn_scope_p,
 		     namespace.  We will still want to insert it if
 		     it is revealing a not-revealed thing.  */
 		  found = true;
-		  if (!revealing_p)
+		  if (old.hidden_p ())
+		    /* The function was merged with a hidden built-in;
+		       insert it again as not hidden.  */
+		    found = false;
+		  else if (!revealing_p)
 		    ;
 		  else if (old.using_p ())
 		    {
@@ -9007,7 +9015,8 @@ pop_nested_namespace (tree ns)
    unqualified search.  */
 
 static void
-add_using_namespace (vec<tree, va_gc> *&usings, tree target)
+add_using_namespace (vec<tree, va_gc> *&usings, tree target,
+		     bool imported = false)
 {
   /* Find if this using already exists.  */
   tree old = NULL_TREE;
@@ -9024,15 +9033,18 @@ add_using_namespace (vec<tree, va_gc> *&usings, tree target)
     {
       decl = build_lang_decl (USING_DECL, NULL_TREE, NULL_TREE);
       USING_DECL_DECLS (decl) = target;
+      DECL_MODULE_IMPORT_P (decl) = imported;
     }
 
-  /* Update purviewness and exportedness in case that has changed.  */
+  /* Update module flags in case that has changed.  */
   if (modules_p ())
     {
       if (module_purview_p ())
 	DECL_MODULE_PURVIEW_P (decl) = true;
       if (module_exporting_p ())
 	DECL_MODULE_EXPORT_P (decl) = true;
+      if (!imported)
+	DECL_MODULE_IMPORT_P (decl) = false;
     }
 
   if (!old)
@@ -9040,13 +9052,14 @@ add_using_namespace (vec<tree, va_gc> *&usings, tree target)
 }
 
 /* Convenience overload for the above, taking the user as its first
-   parameter.  */
+   parameter, for use when importing a using-directive.  */
 
 void
-add_using_namespace (tree ns, tree target)
+add_imported_using_namespace (tree ns, tree target)
 {
   add_using_namespace (NAMESPACE_LEVEL (ns)->using_directives,
-		       ORIGINAL_NAMESPACE (target));
+		       ORIGINAL_NAMESPACE (target),
+		       /*imported=*/true);
 }
 
 /* Tell the debug system of a using directive.  */
@@ -9251,6 +9264,28 @@ make_namespace_finish (tree ns, tree *slot, bool from_import = false)
     add_using_namespace (NAMESPACE_LEVEL (ctx)->using_directives, ns);
 }
 
+/* NS is a possibly-imported namespace that is now needed for
+   a declaration.  Add it to the current TU's binding slot.  */
+
+void
+expose_existing_namespace (tree ns)
+{
+  if (!modules_p ())
+    return;
+
+  tree bind = *find_namespace_slot (CP_DECL_CONTEXT (ns), DECL_NAME (ns));
+  if (bind != ns)
+    {
+      auto &cluster = BINDING_VECTOR_CLUSTER (bind, 0);
+      binding_slot &slot = cluster.slots[BINDING_SLOT_CURRENT];
+      gcc_checking_assert (!(tree)slot || (tree)slot == ns);
+      slot = ns;
+    }
+
+  if (module_purview_p ())
+    DECL_MODULE_PURVIEW_P (ns) = true;
+}
+
 /* Push into the scope of the NAME namespace.  If NAME is NULL_TREE,
    then we enter an anonymous namespace.  If MAKE_INLINE is true, then
    we create an inline namespace (it is up to the caller to check upon
@@ -9332,25 +9367,9 @@ push_namespace (tree name, bool make_inline)
       /* DR2061.  NS might be a member of an inline namespace.  We
 	 need to push into those namespaces.  */
       if (modules_p ())
-	{
-	  for (tree parent, ctx = ns; ctx != current_namespace;
-	       ctx = parent)
-	    {
-	      parent = CP_DECL_CONTEXT (ctx);
-
-	      tree bind = *find_namespace_slot (parent, DECL_NAME (ctx), false);
-	      if (bind != ctx)
-		{
-		  auto &cluster = BINDING_VECTOR_CLUSTER (bind, 0);
-		  binding_slot &slot = cluster.slots[BINDING_SLOT_CURRENT];
-		  gcc_checking_assert (!(tree)slot || (tree)slot == ctx);
-		  slot = ctx;
-		}
-
-	      if (module_purview_p ())
-		DECL_MODULE_PURVIEW_P (ctx) = true;
-	    }
-	}
+	for (tree ctx = ns; ctx != current_namespace;
+	     ctx = CP_DECL_CONTEXT (ctx))
+	  expose_existing_namespace (ctx);
 
       count += push_inline_namespaces (CP_DECL_CONTEXT (ns));
       if (DECL_SOURCE_LOCATION (ns) == BUILTINS_LOCATION)