DIP54 : revamp of Phobos tuple types

[Timon Gehr]

On 12/30/2013 05:11 AM, Dicebot wrote:
> On Monday, 30 December 2013 at 04:07:42 UTC, Timon Gehr wrote:
>>> Template arguments lists are what they are - entities that can be passed
>>> to templates. Aliasing them is sensible but creating values thereof does
>>> not make sense.
>>
>> You are doing it in the implementation of std.typecons.Tuple, and on
>> every variadic function template call. How does it not make sense?
>
> See my clarification here -
> http://forum.dlang.org/post/msumrnieryzifgcyuiqc@forum.dlang.org
>
> It is not creation of instance in general language meaning, it is
> special case implemented specifically for template argument lists which
> just happen to look so naturally close to instantiation. In fact it
> creates new template argument lists of aliases to variables, one can do
> the same trick manually with named variables with exactly same effect.

Just to get your assumption that I am confused out of the way, I am 
fully aware how this is most easily implemented (in fact, I _have_ 
implemented it in my own partly-finished D programming language frontend.)

If you are going to claim that this is not proper creation of an 
instance of a type, except that:

int x;
static assert(is(typeof(x)==int));

Seq!(int, double) y;
static assert(is(typeof(y)==Seq!(int, double))); // presumably "bad"

Then I don't know what to tell you. It is not useful at all to make a 
terminological distinction between the two cases above and claim that 
one is somehow special and confusing, when everything actually behaves 
in an uniform way.