Non-static data member

[Bjorn Reese <breese@…>]

Consider the following example:

  void foo(int value) {}
  struct alpha {
    int value;
    typedef BOOST_TYPEOF(foo(value)) return_type;
  };

This example compiles just fine with g++, but with clang++ it only works if compiled with -std=c++11, otherwise it gives the error message below. I believe that clang is correct (this diagnostics was ​added in clang 3.1.)

Is this a bug in Boost.Typeof or is it expected behavior? Is there a workaround for it?

The error message is:

/home/breese/src/treediff/treediff/main.cpp:17:30: error: invalid use of non-static data member 'value'
    typedef BOOST_TYPEOF(foo(value)) return_type;
                             ^~~~~
/usr/local/include/boost/typeof/native.hpp:41:76: note: expanded from macro 'BOOST_TYPEOF'
#define BOOST_TYPEOF(expr) BOOST_TYPEOF_KEYWORD(boost::type_of::ensure_obj(expr))

    ^
1 error generated.

[Steven Watanabe]

This behavior is expected. There's absolutely nothing that Boost.Typeof can do about it anyway. Workaround: foo(boost::declval<alpha&>().value).