[Bug c++/41933] [c++0x] lambdas and variadic templates don't work together

["akim.demaille at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41933

Akim Demaille <akim.demaille at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |akim.demaille at gmail dot com

--- Comment #9 from Akim Demaille <akim.demaille at gmail dot com> ---
Hi all,

For what it's worth, Wikipedia has a note about this G++ bug:
http://en.wikipedia.org/wiki/Variadic_template .  Below, a test case that
passes with clang, but fails to compile with G++ 4.9.


#include <iostream>

struct pass
{
  template<typename ...T> pass(T...) {}
};

template <typename... T>
void print(T... args)
{
   pass{([&]{ std::cout << args << std::endl; }(), 1)...};
}

int main()
{
  print(1, "2", 3.4, '5');
}


$ g++-mp-4.9 -Wall var.cc -std=c++11
var.cc: In function 'void print(T ...)':
var.cc:11:54: error: expansion pattern '(<lambda>(), 1)' contains no argument
packs
    pass{([&]{ std::cout << args << std::endl; }(), 1)...};
                                                      ^
var.cc: In instantiation of 'void print(T ...) [with T = {int, const char*,
double, char}]':
var.cc:16:25:   required from here
var.cc:11:4: error: no matching function for call to
'pass::pass(<brace-enclosed initializer list>)'
    pass{([&]{ std::cout << args << std::endl; }(), 1)...};
    ^
var.cc:11:4: note: candidates are:
var.cc:5:27: note: template<class ... T> pass::pass(T ...)
   template<typename ...T> pass(T...) {}
                           ^
var.cc:5:27: note:   template argument deduction/substitution failed:
var.cc:3:8: note: constexpr pass::pass(const pass&)
 struct pass
        ^
var.cc:3:8: note:   no known conversion for argument 1 from '<type error>' to
'const pass&'
var.cc:3:8: note: constexpr pass::pass(pass&&)
var.cc:3:8: note:   no known conversion for argument 1 from '<type error>' to
'pass&&'