Re: [boost] [type_traits]is_convertible<noncopyable,To> crashes

From: Alexei Alexandrov (alexei.alexandrov_at_[hidden])
Date: 2006-04-17 06:51:13

JOAQUIN LOPEZ MU?Z <joaquin <at> tid.es> writes:

> 
> OK, I've carefully read the standard and I understand now that
> convertiblity between X and itself is tantamount to
> X being copy constructible (my naive understanding was that
> X is always convertible to X by definition.) For the purposes
> of my code, I can then replace the calls of the form
> 
>   is_convertible<X,Y>
> 
> with calls to
> 
>   template<typename From,typename From>
>   struct is_same_or_convertible:
>     mpl::or_<
>       is_same<From,To>
>       is_convertible<From,To>
>     >
>   {};
> 
> and thus avoid executing is_convertible<From,To> whith
> From=To.
> 

I checked this fix (having fixed some obvious typos in it) out with the test 
case I posted earlier (in multi_index problem thread) - it doesn't help (sigh). 
The error is:

D:\src\3rd-parties\boost/boost/type_traits/is_convertible.hpp(254): error: no 
suitable user-defined conversion from "const name_record" to "const 
base_record" exists
      BOOST_STATIC_CONSTANT(bool, value =
      ^
          detected during:
            instantiation of 
class "boost::detail::is_convertible_basic_impl<From, To> [with 
From=boost::detail::is_convertible_impl<const name_record, const 
base_record>::ref_type, To=const base_record]" at line 286
            instantiation of class "boost::detail::is_convertible_impl<From, 
To> [with From=const name_record, To=const base_record]" at line 362
            instantiation of 
class "boost::detail::is_convertible_impl_dispatch<From, To> [with From=const 
name_record, To=const base_record]" at line 409
            instantiation of class "boost::is_convertible<From, To> [with 
From=const name_record, To=const base_record]" at line 25 of "D:\src\3rd-
parties\boost/boost/mpl/aux_/preprocessed/plain/or.hpp"
            instantiation of class "boost::mpl::aux::or_impl<false, T1, T2, T3, 
T4> [with T1=boost::is_convertible<const name_record, const base_record>, 
T2=boost::mpl::false_, T3=boost::mpl::false_, T4=boost::mpl::false_]" at line 
50 of "D:\src\3rd-parties\boost/boost/mpl/aux_/preprocessed/plain/or.hpp"