Tuple/Typedef question

[Martin via Digitalmars-d-learn]

On Sunday, 11 January 2015 at 11:52:42 UTC, ketmar via 
Digitalmars-d-learn wrote:
> On Sun, 11 Jan 2015 11:41:08 +0000
> Martin via Digitalmars-d-learn 
> <digitalmars-d-learn at puremagic.com>
> wrote:
>
>> Is there a way to get Tuple (and Typedef) from the std.typecons
>> module to generate a new type that is unique on every
>> instantiation? What I mean is:
>> 
>> alias T1 = Tuple!(int, int);
>> alias T2 = Tuple!(int, int);
>> 
>> writeln(__traits(isSame, T1, T2)); // prints true
>> 
>> When using Typedef, the types are still the same:
>> 
>> alias T1New = Typedef!(T1);
>> alias T2New = Typedef!(T2);
>> 
>> writeln(__traits(isSame, T1New, T2New)); // still prints true
>> 
>> The documentation of Typedef says:
>> "Typedef allows the creation of a unique type which is based on
>> an existing type. Unlike the alias feature, Typedef ensures the
>> two types are not considered as equals."
>> 
>> Shouldn't the second part at least print false then?
> as for `Typedef!` -- you can use it's third arg, "cookie":
>
>   import std.typecons;
>
>   alias T1 = Tuple!(int, int);
>   alias T2 = Tuple!(int, int);
>
>   alias T1New = Typedef!(T1, T1.init, "t0");
>   alias T2New = Typedef!(T2, T2.init, "t1");
>
>   pragma(msg, __traits(isSame, T1New, T2New)); // false
>
> there was a heated discussion about `std.typecons.Typedef`, 
> built-in
> `typedef` and other related things, but the decision was to 
> keep the
> status quo.

I can't believe I missed the cookie part. Thanks!