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

[redi at gcc dot gnu.org]

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

--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #9)
> 
>   // template<typename CallRes> struct CheckResult<CallRes, CallRes> :
> std::true_type { };

Sorry, bugzilla wrapped that line, you'll need to join those lines or comment
out the std::true_type too.  Uncommenting it makes it compile.