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From: "ldionne.2 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/59498] New: Pack expansion error in template alias
Date: Fri, 13 Dec 2013 18:34:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59498

            Bug ID: 59498
           Summary: Pack expansion error in template alias
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ldionne.2 at gmail dot com

GCC Version
-----------
gcc-4.9 (GCC) 4.9.0 20131201 (experimental)
Installed with Homebrew.


System
------
OS X 10.8.5


Command line to trigger the bug
-------------------------------
gcc-4.9 -std=c++11 -Wall -Wextra -pedantic -o /dev/null -c
template_alias_bug.cpp


Minimal code to reproduce
-------------------------

    template <typename T, typename ...>
    using alias = T;

    template <typename ...T>
    using variadic_alias = alias<T...>;

    using Fail = variadic_alias<int>;

    int main() { }


Error message
-------------
template_alias_bug.cpp:9:34: error: pack expansion argument for non-pack
parameter 'T' of alias template 'template<class T, class ...> using alias = T'
 using variadic_alias = alias<T...>;
                                  ^
template_alias_bug.cpp:5:11: note: declared here
 template <typename T, typename ...>
           ^
template_alias_bug.cpp:11:14: error: expected type-specifier before
'variadic_alias'
 using Fail = variadic_alias<int>;
              ^

Possibly related
----------------
Bug 58856


Comments
--------
Clang compiles the code just fine and I don't see any obvious reason why that
would be invalid C++11 (I could be mistaken), so I think that's a GCC bug.