I dun a DIP, possibly the best DIP ever

[Stefan Koch]

On Thursday, 23 April 2020 at 20:23:03 UTC, Steven Schveighoffer 
wrote:
> On 4/23/20 4:08 PM, Stefan Koch wrote:
>> On Thursday, 23 April 2020 at 19:27:31 UTC, Steven 
>> Schveighoffer wrote:
>>> On 4/23/20 3:02 PM, Stefan Koch wrote:
>>>> On Thursday, 23 April 2020 at 18:57:04 UTC, Steven 
>>>> Schveighoffer wrote:
>>>>> [...]
>>>>
>>>> It's the latter.
>>>> you cannot re-expand.
>>>
>>> Those 2 are contradictory statements.
>>>
>>> If it's the latter, then tuple1... is expanded to a tuple 
>>> that is then used in the outer expansion.
>>>
>> 
>> k tuples with n elements can only expand to 1 tuple with k*n 
>> elements.
>> They can't get more.
>
> You have lost me.
>
> Can you go through a blow-by-blow of how this nested expansion 
> happens?
>
> alias tuple1 = AliasSeq!(1, 2, 3);
> alias tuple2 = AliasSeq!(4, 5, 6)
>
> AliasSeq!(tuple1..., tuple2)...
>
> -Steve

This nested expression does not parse.
And I don't think it should.
Because we cannot nest tuples in tuples.