Re: [boost] [type traits] possible bug in boost::is_convertible for types with private copy constructors

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2008-06-26 13:40:28

On Jun 26, 2008, at 1:30 PM, David Abrahams wrote:

> Howard Hinnant wrote:
>> On Jun 26, 2008, at 12:33 PM, David Abrahams wrote:
>>
>>> At least one thing is clear: is_convertible shouldn't ever cause a
>>> compile-time error.  If one of the possible implementations always
>>> avoids a compile-time error, I vote for that one.
>>
>> I believe the only time you can get a compile-time error out of
>> is_convertible is if you use it with types which fail to meet these
>> requirements:
>>
>>> From and To shall be complete types, arrays of unknown bound, or
>>> (possibly cv-qualified) void types.
>>

<chuckle> Touché. :-)

std::is_convertible is supposed to get access correct.  The only way  
we currently know how to do that is with compiler help.

Library implementations, no matter whether they treat From as an  
lvalue or rvalue, are apparently doomed to fail to compile when there  
is an access violation.

-Howard