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

[redi at gcc dot gnu.org]

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

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> ---
If this isn't a regression (which it doesn't seem to be) then setting Target
Milestone to 4.8.4 doesn't seem appropriate.