commit 506d5f399bef7f2d8c48fd83d853c6ff7811a226
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Jul 26 10:39:34 2023 -0400

    c++: member vs global template [PR106310]
    
    For backward compatibility we still want to allow patterns like
    this->A<T>::foo, but the template keyword in a qualified name is
    specifically to specify that a dependent name is a template, so don't look
    in the enclosing scope at all.
    
    Also fix handling of dependent bases: if member lookup in the current
    instantiation fails and we have dependent bases, the lookup is dependent.
    We were already handling that for the case where lookup in the enclosing
    scope also fails, but we also want it to affect that lookup itself.
    
            PR c++/106310
    
    gcc/cp/ChangeLog:
    
            * parser.c (cp_parser_template_name): Skip non-member
            lookup after the template keyword.
            (cp_parser_lookup_name): Pass down template_keyword_p.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/template/template-keyword4.C: New test.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 8287934a679..8df715596eb 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -2610,7 +2610,7 @@ static tree cp_parser_objc_struct_declaration
 /* Utility Routines */
 
 static cp_expr cp_parser_lookup_name
-  (cp_parser *, tree, enum tag_types, bool, bool, bool, tree *, location_t);
+  (cp_parser *, tree, enum tag_types, int, bool, bool, tree *, location_t);
 static tree cp_parser_lookup_name_simple
   (cp_parser *, tree, location_t);
 static tree cp_parser_maybe_treat_template_as_class
@@ -17748,7 +17748,7 @@ cp_parser_template_name (cp_parser* parser,
   /* Look up the name.  */
   decl = cp_parser_lookup_name (parser, identifier,
 				tag_type,
-				/*is_template=*/true,
+				/*is_template=*/1 + template_keyword_p,
 				/*is_namespace=*/false,
 				check_dependency_p,
 				/*ambiguous_decls=*/NULL,
@@ -29254,7 +29254,7 @@ prefer_type_arg (tag_types tag_type)
    refer to types are ignored.
 
    If IS_TEMPLATE is TRUE, bindings that do not refer to templates are
-   ignored.
+   ignored.  If IS_TEMPLATE IS 2, the 'template' keyword was specified.
 
    If IS_NAMESPACE is TRUE, bindings that do not refer to namespaces
    are ignored.
@@ -29269,7 +29269,7 @@ prefer_type_arg (tag_types tag_type)
 static cp_expr
 cp_parser_lookup_name (cp_parser *parser, tree name,
 		       enum tag_types tag_type,
-		       bool is_template,
+		       int is_template,
 		       bool is_namespace,
 		       bool check_dependency,
 		       tree *ambiguous_decls,
@@ -29454,7 +29454,14 @@ cp_parser_lookup_name (cp_parser *parser, tree name,
       else
 	decl = NULL_TREE;
 
-      if (!decl)
+      /* If we didn't find a member and have dependent bases, the member lookup
+	 is now dependent.  */
+      if (!dep && !decl && any_dependent_bases_p (object_type))
+	dep = true;
+
+      if (dep && is_template == 2)
+	/* The template keyword specifies a dependent template.  */;
+      else if (!decl)
 	/* Look it up in the enclosing context.  DR 141: When looking for a
 	   template-name after -> or ., only consider class templates.  */
 	decl = lookup_name (name, is_namespace ? LOOK_want::NAMESPACE
diff --git a/gcc/testsuite/g++.dg/template/template-keyword4.C b/gcc/testsuite/g++.dg/template/template-keyword4.C
new file mode 100644
index 00000000000..a7ab9bb8ca6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/template-keyword4.C
@@ -0,0 +1,18 @@
+// PR c++/106310
+
+template <class T>
+struct set{};
+
+template< typename T >
+struct Base
+{
+  template< int > int set(T const &);
+};
+
+template< typename T >
+struct Derived : Base< T >
+{
+  void f(T const &arg) {
+    this->template set< 0 >(arg);
+  }
+};