[Bug c++/58569] New: Compilation error when copying class which contains multiple std::function

[pierre.krieger1708 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58569

            Bug ID: 58569
           Summary: Compilation error when copying class which contains
                    multiple std::function
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pierre.krieger1708 at gmail dot com

Created attachment 30924
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30924&action=edit
The preprocessed file

This simple code snippet fails to compile:


#include <functional>

struct foo {
  std::function<foo (int)> x;
  std::function<foo ()> y;
};

int main(int argc, char const* argv[]) {
  foo a;  
  return 0;
}


The problem happens if a class contains at least two std::function of different
type which return the class itself.

If you remove the "int" from "foo (int)", it works. If you remove either member
"x" or "y", it works.


With g++4.8.1 and flag -std=c++11:

In file included from test.cpp:1:0:
/usr/include/c++/4.8/functional: In instantiation of ‘struct
std::function<foo()>::_CheckResult<foo, foo>’:
/usr/include/c++/4.8/functional:2192:63:   required by substitution of
‘template<class _Res, class ... _ArgTypes> template<class _Cond, class _Tp>
using _Requires = typename std::enable_if<_Cond:: value, _Tp>::type [with _Cond
= std::function<foo()>::_CheckResult<foo, foo>; _Tp = void; _Res = foo;
_ArgTypes = {}]’
/usr/include/c++/4.8/functional:2254:9:   required by substitution of
‘template<class _From1, class _To1> static decltype
((__test_aux<_To1>(declval<_From1>()), std::__sfinae_types::__one()))
std::__is_convertible_helper<_From, _To, false>::__test(int) [with _From1 =
_From1; _To1 = _To1; _From = foo; _To = foo] [with _From1 = foo; _To1 = foo]’
/usr/include/c++/4.8/type_traits:1312:50:   required from ‘constexpr const bool
std::__is_convertible_helper<foo, foo, false>::value’
/usr/include/c++/4.8/type_traits:1317:12:   required from ‘struct
std::is_convertible<foo, foo>’
/usr/include/c++/4.8/functional:2181:9:   required from ‘struct
std::function<foo(int)>::_CheckResult<foo, foo>’
/usr/include/c++/4.8/functional:2192:63:   required by substitution of
‘template<class _Res, class ... _ArgTypes> template<class _Cond, class _Tp>
using _Requires = typename std::enable_if<_Cond:: value, _Tp>::type [with _Cond
= std::function<foo(int)>::_CheckResult<foo, foo>; _Tp = void; _Res = foo;
_ArgTypes = {int}]’
/usr/include/c++/4.8/functional:2254:9:   required from here
/usr/include/c++/4.8/functional:2181:9: error: invalid use of incomplete type
‘struct std::is_convertible<foo, foo>’
  struct _CheckResult
         ^
In file included from /usr/include/c++/4.8/bits/move.h:57:0,
                 from /usr/include/c++/4.8/bits/stl_pair.h:59,
                 from /usr/include/c++/4.8/utility:70,
                 from /usr/include/c++/4.8/tuple:38,
                 from /usr/include/c++/4.8/functional:55,
                 from test.cpp:1:
/usr/include/c++/4.8/type_traits:1317:12: error: declaration of ‘struct
std::is_convertible<foo, foo>’
     struct is_convertible
            ^
/usr/include/c++/4.8/type_traits: In substitution of ‘template<class _From1,
class _To1> static decltype ((__test_aux<_To1>(declval<_From1>()),
std::__sfinae_types::__one())) std::__is_convertible_helper<_From, _To,
false>::__test(int) [with _From1 = _From1; _To1 = _To1; _From = foo; _To = foo]
[with _From1 = foo; _To1 = foo]’:
/usr/include/c++/4.8/type_traits:1312:50:   required from ‘constexpr const bool
std::__is_convertible_helper<foo, foo, false>::value’
/usr/include/c++/4.8/type_traits:1317:12:   required from ‘struct
std::is_convertible<foo, foo>’
/usr/include/c++/4.8/functional:2181:9:   required from ‘struct
std::function<foo(int)>::_CheckResult<foo, foo>’
/usr/include/c++/4.8/functional:2192:63:   required by substitution of
‘template<class _Res, class ... _ArgTypes> template<class _Cond, class _Tp>
using _Requires = typename std::enable_if<_Cond:: value, _Tp>::type [with _Cond
= std::function<foo(int)>::_CheckResult<foo, foo>; _Tp = void; _Res = foo;
_ArgTypes = {int}]’
/usr/include/c++/4.8/functional:2254:9:   required from here
/usr/include/c++/4.8/type_traits:1302:21: error:   initializing argument 1 of
‘static void std::__is_convertible_helper<_From, _To, false>::__test_aux(_To1)
[with _To1 = foo; _From = foo; _To = foo]’
         static void __test_aux(_To1);