Missing Boost header in camp/detail/raw_type.hpp

[fmauger]

The "boost::enable_if" struct is used in file "camp/detail/rawtype.hpp" but there is no proper Boost include. This causes an error while compiling my project with GCC 9.3 (and Boost 1.71) which includes "camp/detail/typeid.hpp"
then "camp/detail/objecttraits.hpp" then "camp/detail/rawtype.hpp".
I wonder why this has not been detected before. Maybe there is some change in the way GCC process templates...
Formerly I was using gcc4.9 and gcc7 with Boost 1.69 and it was ok.

Having a look on some Camp headers, the "#include <boost/utility/enable_if.hpp>" header is often (if not always) included after dependee Camp headers so that, depending on the way we use/include Camp stuff, this issue is not detected if the client code has its own enable_if include somewhere.
I will suggest to include first dependee Boost headers before Camp ones as a general rule... unless someone has a strong argument against this approach.

[fmauger]

If I change the includes' ordering in "camp/detal/typeid.hpp", it compiles again.
Details on my compiler error log:

In file included from /usr/include/camp/detail/objecttraits.hpp:37,
                 from /usr/include/camp/detail/typeid.hpp:37,
                 from my own foo.h
...
/usr/include/camp/detail/rawtype.hpp:100:38: error: ‘enable_if’ in namespace ‘boost’ does not name a template type
  100 | struct RawType, typename boost::enable_if, U> >::type>
      |                                      ^~~~~~~~~
/usr/include/camp/detail/rawtype.hpp:100:47: error: expected template-argument before ‘<’ token
  100 | struct RawType, typename boost::enable_if, U> >::type>
      |                                               ^
/usr/include/camp/detail/rawtype.hpp:100:47: error: expected ‘>’ before ‘<’ token
/usr/include/camp/detail/rawtype.hpp:100:79: error: template argument 2 is invalid
  100 | struct RawType, typename boost::enable_if, U> >::type>
      |                                                                               ^