Re: [boost] [utility] Adding noexcept to boost::declval

Subject: Re: [boost] [utility] Adding noexcept to boost::declval
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2012-03-26 22:00:08

AMDG

On 03/26/2012 06:19 PM, Michel Morin wrote:
> Vicente J. Botet Escriba wrote
>>> Summary:
>>> Defining declval<T>() as add_lvalue_reference<T>::type is wrong;
>>> add_lvalue_reference should be removed!
>>>
>>>
>> There is something that disturb me by returning just T, doesn't this forces
>> the type T to CopyConstructible?
> 
> Nope. T needs not to be CopyConstructible
> (Note that declval can be used only in unevaluated contexts.)
> 

Even if it doesn't have to be CopyConstructible,
it still can't be an abstract class.  On the
other hand, maybe that's okay, since in C++03,
there's no way to create an rvalue of an abstract
class.

> 
>> The idea to use T& instead was to avoid
>> this.
> 
> You shouldn't do this, because this transforms rvalues to lvalues.
> 
> 
>> I have rolled back at revision 77562.
> 
> Thanks, Vicente!
> Minor issue: `#include <boost/type_traits/add_lvalue_reference.hpp>` is
> not removed yet.
> 

In Christ,
Steven Watanabe