[Bug c++/48292] New: [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[Bug c++/48292] New: [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[zeratul976 at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

           Summary: [C++0x] "sorry, unimplemented: use of
                    'type_pack_expansion' in template"
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: zeratul976@hotmail.com


For the following code:

template <typename... Args> int g(Args...);

template <int N = 0>
struct A
{
    template <typename... Args>
    static auto f(Args... args) -> decltype(g(args...));
};

int main()
{
    A<>::f();
    return 0;
}

gcc gives the following errors:

test.cpp: In function 'int main()':
test.cpp:7:27: sorry, unimplemented: use of 'type_pack_expansion' in template
test.cpp:12:12: error: no matching function for call to 'A<>::f()'
test.cpp:12:12: note: candidate is:
test.cpp:7:55: note: template<class ... Args> static decltype (g(A::f::args
...)) A::f(Args ...) [with Args = {Args ...}, int N = 0, decltype (g(A::f::args
...)) = int]

Are there any plans to implement this?

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[zeratul976 at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

--- Comment #1 from Nathan Ridge <zeratul976 at hotmail dot com> 2011-03-25 23:52:22 UTC ---
Also, does someone know a workaround for this?

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[zeratul976 at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

--- Comment #2 from Nathan Ridge <zeratul976 at hotmail dot com> 2011-03-26 00:02:32 UTC ---
Found a workaround:

#include <type_traits>

template <typename... Args> 
int g(Args...);

template <typename... Args>
struct deduce
{
    typedef decltype(g(std::declval<Args>()...)) type;
};

template <int N = 0>
struct A
{
    template <typename... Args>
    static typename deduce<Args...>::type f(Args... args);
};

int main()
{
    A<>::f();
    return 0;
}

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-03-28 16:27:43 UTC ---
CC-ing Jason about this one too. By the way, isn't the first time this sorry
message surfaces, eg, Comment #4 in PR44167.

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marc.hofmann at gmail dot
                   |                            |com

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-24 12:44:35 UTC ---
*** Bug 44167 has been marked as a duplicate of this bug. ***

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-24 12:50:45 UTC ---
(In reply to comment #3)
> CC-ing Jason about this one too. By the way, isn't the first time this sorry
> message surfaces, eg, Comment #4 in PR44167.

... actually adding Jason to the CC list ;)

I've marked the other as a dup after comparing the results for both testcases
with G++ 4.4 and later versions.

Jason, is this likely to be easy to fix?  I've been hitting this and PR 47335
while implementing std::allocator_traits.  If they aren't likely to be fixed in
the near future I'll look into workarounds

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2011.05.25 03:17:26
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-25 09:05:15 UTC ---
Jason, I've found a decent workaround now so if you have higher priority issues
you'd rather fix then don't spend time on this one for my benefit. Thanks for
the incredible number of fixes you're making at the moment!

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2011-05-25 14:32:09 UTC ---
Author: jason
Date: Wed May 25 14:32:06 2011
New Revision: 174201

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=174201
Log:
    PR c++/48292
    * pt.c (tsubst_decl) [PARM_DECL]: Handle partial instantiation of
    function parameter pack.
    (tsubst_pack_expansion): Likewise.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/variadic109.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

--- Comment #8 from Jason Merrill <jason at gcc dot gnu.org> 2011-05-25 15:26:18 UTC ---
Author: jason
Date: Wed May 25 15:26:14 2011
New Revision: 174207

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=174207
Log:
    PR c++/48292
    * pt.c (tsubst_decl) [PARM_DECL]: Handle partial instantiation of
    function parameter pack.
    (tsubst_pack_expansion): Likewise.

Added:
    branches/gcc-4_6-branch/gcc/testsuite/g++.dg/cpp0x/variadic109.C
Modified:
    branches/gcc-4_6-branch/gcc/cp/ChangeLog
    branches/gcc-4_6-branch/gcc/cp/pt.c
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog

[Bug c++/48292] [C++0x] "sorry, unimplemented: use of 'type_pack_expansion' in template"

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48292

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.6.1

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> 2011-05-25 15:29:42 UTC ---
Fixed for 4.6.1.