Multiple alias this, what's the hold up?

[Jonathan Marler]

On Wednesday, 19 June 2019 at 05:53:42 UTC, Jonathan M Davis 
wrote:
> On Tuesday, June 18, 2019 10:09:24 PM MDT Mike Franklin via 
> Digitalmars-d wrote:
>> On Tuesday, 18 June 2019 at 22:51:51 UTC, Jonathan M Davis 
>> wrote:
>> > It definitely looks like a DIP would be required for 
>> > multiple alias this-es to become a thing, and whatever was 
>> > in the DIP would have to convince Walter that it doesn't 
>> > have the problems that multiple inheritance has.
>>
>> DIP66 (https://wiki.dlang.org/DIP66) was already created and 
>> approved.  Did you have something else in mind?
>
> Given Walter's more recent statements on the matter, it doesn't 
> sound like it's approved anymore. He's repeatedly compared 
> having multiple alias this-es to multiple inheritance and 
> expressed that it's a bad idea.
>
> - Jonathan M Davis

It's fair to say that multiple alias this and multiple 
inheritance have similarities, but some have argued that the "bad 
parts" of multiple inheritance don't apply to 'alias this' (i.e. 
the "Diamond Problem").  I'm hoping Walter will reveal what 
problems he claims apply to both as I haven't seen anyone else 
point them out yet.