[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 #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
And it should only happen when instantiating the converting constructor
template or converting assignment operator function, not when instantiating the
class template.