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.
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