[Bug c++/34023] Wrong using of user-defined conversion operator for converting rvalue to reference on constant.

["sergey dot gcc at comrades dot id dot au" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from sergey dot gcc at comrades dot id dot au  2007-11-29 00:04 -------
(In reply to comment #3)
> // Workaround:
> class a
> {
> public:
>         template<class T>
>         operator T &() const
>                 throw(typename ::boost::disable_if<
>                         ::boost::is_same<T, ref_t const> >::type *)
>         {
>                 static int f;
>                 return f;
>         }
> };
> 
> int main()
> {
>         a const &aa = a(); // line # 27
>         int &i = aa;
> }
> 

This workaround should not work, according to the standard

14.8.2.2

    - All references in the function type of the function template to the
corresponding template parameters are replaced by the specified template
argument values. If a substitution in a template parameter or in the function
type of the function template results in an invalid type, type deduction fails.
[Note: The equivalent substitution in exception specifications is done only
when the function is instantiated, at which point a program is ill-formed if
the substitution results in an invalid type.] Type deduction may fail for the
following reasons:

However, it works on GCC. It is another bug in GCC.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34023