Build failure: function_template.hpp:159:33: error: called object type 'nullptr_t' is not a function or function pointer

[yuri <yuri@…>]

RStudio-1.1.409_1 fails to build with clang on FreeBSD-12:

/usr/ports/devel/RStudio/work/rstudio-1.1.409/src/cpp/core/system/Process.cpp
In file included from /wrkdirs/usr/ports/devel/RStudio/work/rstudio-1.1.409/src/cpp/core/system/Process.cpp:16:
In file included from /wrkdirs/usr/ports/devel/RStudio/work/rstudio-1.1.409/src/cpp/core/include/core/system/Process.hpp:25:
In file included from /usr/local/include/boost/function.hpp:70:
In file included from /usr/local/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:57:
In file included from /usr/local/include/boost/function/detail/function_iterate.hpp:14:
In file included from /usr/local/include/boost/function/detail/maybe_include.hpp:29:
/usr/local/include/boost/function/function_template.hpp:159:33: error: called object type 'nullptr_t' is not a function or function pointer
          BOOST_FUNCTION_RETURN((*f)(BOOST_FUNCTION_ARGS));
                                ^~~~
/usr/local/include/boost/function/function_template.hpp:81:36: note: expanded from macro 'BOOST_FUNCTION_RETURN'
#  define BOOST_FUNCTION_RETURN(X) X
                                   ^
/usr/local/include/boost/function/function_template.hpp:925:53: note: in instantiation of member function 'boost::detail::function::void_function_obj_invoker2<nullptr_t, void, bool, bool>::invoke' requested here
        { { &manager_type::manage }, &invoker_type::invoke };
                                                    ^
/usr/local/include/boost/function/function_template.hpp:716:13: note: in instantiation of function template specialization 'boost::function2<void, bool, bool>::assign_to<nullptr_t>' requested here
      this->assign_to(f);
            ^
/usr/local/include/boost/function/function_template.hpp:1061:5: note: in instantiation of function template specialization 'boost::function2<void, bool, bool>::function2<nullptr_t>' requested here
    base_type(f)
    ^
/usr/local/include/boost/function/function_template.hpp:1114:5: note: in instantiation of function template specialization 'boost::function<void (bool, bool)>::function<nullptr_t>' requested here
    self_type(f).swap(*this);
    ^
/wrkdirs/usr/ports/devel/RStudio/work/rstudio-1.1.409/src/cpp/core/system/Process.cpp:239:21: note: in instantiation of function template specialization 'boost::function<void (bool, bool)>::operator=<nullptr_t>' requested here
   cb.onHasSubprocs = NULL;
                    ^

[anonymous]

with 1_55 too boost_1_55_0/boost/function/function_template.hpp:153:33: error: called object type 'nullptr_t' is not a function or function pointer

BOOST_FUNCTION_RETURN((*f)(BOOST_FUNCTION_ARGS));