[Bug c++/59759] internal compiler error: in unify, using std::enable_if on classes

[gereon.kremer at cs dot rwth-aachen.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59759

--- Comment #4 from Gereon Kremer <gereon.kremer at cs dot rwth-aachen.de> ---
Created attachment 31838
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31838&action=edit
Reduced example