[process][type_erasure] Including both process and type_erasure creates duplicate definitions in mp11 and fusion

From: Jared McIntyre (jmcintyre_at_[hidden])
Date: 2019-06-21 15:11:09

I've found that type_erasure::any and process::child conflict with each
other in how they use mp11 and fusion. The issue may be specific to
compiling the process library on Windows as it occurs in calls through
detail headers in the library that are specific to Windows, and I haven't
tested on other platforms..

#include <boost/type_erasure/any.hpp>
#include <boost/process/child.hpp>

Order doesn't matter.

1>c:\<removed>\boost\boost\fusion\adapted\std_tuple\tag_of.hpp(38): error
C2953: 'boost::mpl::sequence_tag<std::tuple<_Types...>>': class template
has already been defined
1>c:\<removed>\boost\boost\mp11\mpl.hpp(155): note: see declaration of
'boost::mpl::sequence_tag<std::tuple<_Types...>>'

Boost 1.67, 1.70
VS 2017 (5.9.12)