c++: Variable template and template parameter pack [PR96218]

This is DR 2032 which says that the restrictions regarding template
parameter packs and default arguments apply to variable templates as
well, but we weren't detecting that.

gcc/cp/ChangeLog:

	DR 2032
	PR c++/96218
	* pt.c (check_default_tmpl_args): Also consider variable
	templates.

gcc/testsuite/ChangeLog:

	DR 2032
	PR c++/96218
	* g++.dg/cpp1y/var-templ67.C: New test.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 72bdf869b55cd805003d439d664d5eeeada3fb21..bd2af8b6679f81b603774dbdc76cbffeb97ffec9 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -5482,14 +5482,15 @@ check_default_tmpl_args (tree decl, tree parms, bool is_primary,
                       /* Don't complain about an enclosing partial
                          specialization.  */
                       && parm_level == parms
-                      && TREE_CODE (decl) == TYPE_DECL
+                      && (TREE_CODE (decl) == TYPE_DECL || VAR_P (decl))
                       && i < ntparms - 1
                       && template_parameter_pack_p (TREE_VALUE (parm))
                       /* A fixed parameter pack will be partially
                          instantiated into a fixed length list.  */
                       && !fixed_parameter_pack_p (TREE_VALUE (parm)))
                {
-                 /* A primary class template can only have one
+                 /* A primary class template, primary variable template
+                    (DR 2032), or alias template can only have one
                     parameter pack, at the end of the template
                     parameter list.  */
 

diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ67.C b/gcc/testsuite/g++.dg/cpp1y/var-templ67.C
new file mode 100644 (file)
index 0000000..f36af39
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ67.C
@@ -0,0 +1,16 @@
+// DR 2032 - Default template-arguments of variable templates
+// PR c++/96218
+// { dg-do compile { target c++14 } }
+
+// [temp.param]/14: If a template-parameter of a class template, variable
+// template, or alias template has a default template-argument, each subsequent
+// template-parameter shall either have a default template-argument supplied or
+// be a template parameter pack.
+template<typename T = int, typename U>
+T vt; // { dg-error "no default argument" }
+
+// [temp.param]/14: If a template-parameter of a primary class template,
+// primary variable template, or alias template is a template parameter pack,
+// it shall be the last template-parameter.
+template<typename... Ts, typename U> // { dg-error "must be at the end" }
+int vt2;