[Bug c++/69470] [concepts] bogus constrained member class template redeclared with different access

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69470

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Vedran Miletic from comment #1)
> Happens when building ns-3 [1] too.
> 
> [1016/2462] Compiling src/wifi/model/wifi-mac-queue.cc
> In file included from ./ns3/test.h:24:0,
>                  from ../src/spectrum/test/tv-helper-distribution-test.cc:23:
> /usr/include/c++/6.0.0/sstream:300:7: error: ‘struct
> std::__cxx11::basic_stringbuf<_CharT, _Traits, _Alloc>::__xfer_bufptrs’
> redeclared with different access
>        struct __xfer_bufptrs
>        ^~~~~~

That was a different bug, not related to concepts.