------- Comment #1 from rodolfo at rodsoft dot org  2010-07-21 02:49 -------
The code I posted was meant to be compiled in c++0x mode, but if we write
directly the definition of std::enable_if, it also happens in c++03 mode.
So, instead of #include <type_traits>, one should write:

template <bool B, class T=void> struct enable_if;

template <class T>
struct enable_if<true,T> 
{  
    typedef T type;
};

Of course, I forgot to add the error messages:

teste.cpp:30: error: ambiguous class template instantiation for ‘struct
foo<bar<2>, bar<2>, void>’
teste.cpp:19: error: candidates are: struct foo<V<M>, V<M>, typename
enable_if<((M == RUNTIME) || (M == 2)), void>::type>
teste.cpp:25: error:                 struct foo<V1<M>, V2<M>, typename
enable_if<((M == RUNTIME) || (M == 2)), void>::type>
teste.cpp:30: error: aggregate ‘foo<bar<2>, bar<2>, void> x’ has incomplete
type and cannot be defined


-- 

rodolfo at rodsoft dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rodolfo at rodsoft dot org
           Keywords|                            |rejects-valid
      Known to fail|                            |4.4.3 4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45012