Re: [v3 PATCH] Implement N4387 and LWG 2367

[Marc Glisse <marc.glisse@inria.fr>]

On Sun, 7 Jun 2015, Ville Voutilainen wrote:

> On 7 June 2015 at 11:12, Ville Voutilainen <ville.voutilainen@gmail.com> wrote:
>>> Does the following code still compile with your patch?
>>> struct A { int a,b; };
>>> std::tuple<int,int,A> a(3,4,{1,2});
>>
>> No. :/ And we have no test for it.. I'll need to look at that.
>
> Ahem, yes, this is because the constructor that used to take _Elements
> now takes _UElements. I can change it back to take _Elements, because
> the technique that the default constructors use allow making the signature
> dependent enough that it will sfinae correctly.

Yes.

>>> You use a lot: typename enable_if<X, bool>::type=true
>>> while the current code seems to favor: class=typename enable_if<X>::type.
>>> I don't really care which one is used, but it is easier to read when the
>>> style is consistent through the library.
>> It's not a style issue. That template parameter needs to be a non-type one,
>> otherwise the overloads are ambiguous.

Ah, I had overlooked that. I have seen several work-arounds for this 
issue, but I don't remember this one, it seems nice.

-- 
Marc Glisse