Re: [boost] boost::is_convertible failure on abstract classes

From: John Maddock (john_at_[hidden])
Date: 2005-03-24 12:23:00

> The code below does not compile, when, I believe, it
> should. Compiler says that you can't instantiate
> abstact class.
>
> I'm really surprised - it is trivial use case, but I
> did not find a problem report. Do I miss something?

This is a tricky one; first the headline news: current cvs will compile 
that, and will report false whenever the "To" type is abstract, but only if 
you have a newish compiler that supports is_abstract.  The reason for 
returning false, is that nothing is ever convertible to an abstract type, 
since no object of an abstract type can ever be created.

Now for the problem: is general is_convertible<A,A> may not compile if A's 
copy-constructor is non-public.  We'd love to be able to fix that, but no 
one knows how to detect whether a member is accessible or not.

HTH,

John.