Re: [boost] [mpl] [type_traits] [enable_if] Overloading Problem with GCC 3.3.3

Subject: Re: [boost] [mpl] [type_traits] [enable_if] Overloading Problem with GCC 3.3.3
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2009-12-08 15:24:17

On Tue, 8 Dec 2009, Stewart, Robert wrote:

> Can anyone figure out why GCC 3.3.3 doesn't like the following member function overloads?  VC7/8/9 and GCC 4.1.2 have no problems with this code.
>
> #include <boost/mpl/and.hpp>
> #include <boost/mpl/not.hpp>
> #include <boost/type_traits/is_const.hpp>
> #include <boost/type_traits/is_convertible.hpp>
> #include <boost/utility/enable_if.hpp>
>
> struct Bar
> {
> };
>
> template <class T>
> struct Baz
> {
> };
>
> struct Foo
> {
>   template <class T>
>   typename boost::enable_if
>   <
>      boost::mpl::and_
>      <
>         boost::is_convertible<T,Bar>
>         , boost::mpl::not_<boost::is_const<T> >
>      >
>   >::type
>   set(Baz<T> const & _value);
>
>   template <class T>
>   typename boost::enable_if
>   <
>      boost::mpl::and_
>      <
>         boost::is_convertible<T,Bar>
>         , boost::is_const<T>
>      >
>   >::type
>   set(Baz<T> const &);
> };
>
> GCC 3.3.3's error message is:
>
> error: `template<class T> typename
>   boost::enable_if<boost::mpl::and_<boost::is_convertible<T, Bar>,
>   boost::is_const<T>, mpl_::bool_<true>, mpl_::bool_<true>, mpl_::bool_<true>
>   >, void>::type Foo::set(const Baz<T>&)' and `template<class T> typename
>   boost::enable_if<boost::mpl::and_<boost::is_convertible<T, Bar>,
>   boost::mpl::not_<boost::is_const<T> >, mpl_::bool_<true>, mpl_::bool_<true>,
>   mpl_::bool_<true> >, void>::type Foo::set(const Baz<T>&)' cannot be
>   overloaded

The functions are too similar for GCC 3.3.  Please look at Section 3.4 of 
http://www.boost.org/doc/libs/1_41_0/libs/utility/enable_if.html for more 
information and workarounds.

-- Jeremiah Willcock