Re: [PATCH] c++: unexpanded pack in var tmpl partial spec [PR100652]

[Jason Merrill via Gcc-patches]

On 11/8/21 09:45, Patrick Palka wrote:

Here we're not spotting a bare parameter pack appearing in the argument
list of a variable template partial specialization because we only look
for them within the decl's TREE_TYPE, which is sufficient for class
templates but not for variable templates.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

OK.

        PR c++/100652

gcc/cp/ChangeLog:

        * pt.c (push_template_decl): Check for bare parameter packs in
        the argument list of a variable template partial specialization.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp1y/var-templ69.C: New test.
---
  gcc/cp/pt.c                              | 17 ++++++++++++-----
  gcc/testsuite/g++.dg/cpp1y/var-templ69.C |  5 +++++
  2 files changed, 17 insertions(+), 5 deletions(-)
  create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ69.C

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index b82b9cc3cd2..991a20a85d4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -5877,12 +5877,19 @@ push_template_decl (tree decl, bool is_friend)
        if (check_for_bare_parameter_packs (TYPE_RAISES_EXCEPTIONS (type)))
        TYPE_RAISES_EXCEPTIONS (type) = NULL_TREE;
      }
-  else if (check_for_bare_parameter_packs (is_typedef_decl (decl)
-                                          ? DECL_ORIGINAL_TYPE (decl)
-                                          : TREE_TYPE (decl)))
+  else
      {
-      TREE_TYPE (decl) = error_mark_node;
-      return error_mark_node;
+      if (check_for_bare_parameter_packs (is_typedef_decl (decl)
+                                         ? DECL_ORIGINAL_TYPE (decl)
+                                         : TREE_TYPE (decl)))
+       {
+         TREE_TYPE (decl) = error_mark_node;
+         return error_mark_node;
+       }
+
+      if (is_partial && VAR_P (decl)
+         && check_for_bare_parameter_packs (DECL_TI_ARGS (decl)))
+       return error_mark_node;
      }

if (is_partial)

diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ69.C 
b/gcc/testsuite/g++.dg/cpp1y/var-templ69.C
new file mode 100644
index 00000000000..420d617368c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ69.C
@@ -0,0 +1,5 @@
+// PR c++/100652
+// { dg-do compile { target c++14 } }
+
+template<class...> int var;
+template<class... Ts> char var<bool, Ts>; // { dg-error "parameter packs not 
expanded" }