[Bug c++/60842] In-class initializer causes a strange error

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60842

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
N.B. the simplest workaround is:

    J<int, N::I> j{};