DIP66 - Multiple alias this

[Andrei Alexandrescu]

On 9/29/20 9:42 PM, Mike wrote:
> On Wednesday, 30 September 2020 at 01:36:59 UTC, Mike wrote:
> 
>> So, here are a couple of proposals off the top of my head.  I imagine 
>> someone more talented than I can think of a few more:
>>
>> 1.  Deprecate `alias this` for classes, and implement multiple `alias 
>> this` for structs.  That will give users the composition feature they 
>> need, and in addition, because structs cannot inherit, it removes the 
>> complexity Walter spoke of.
>>
>> 2.  Add `opImplicit`, implicit copy constructors, or something of that 
>> ilk.  Then users only need to forward members using D's 
>> metaprogramming facilities.  Both uses of `alias this` are covered, 
>> but no `alias this` is required.  `alias this` can then be deprecated 
>> entirely.
>>
>> 3.  Add struct inheritance like C++.
> 
> 4. Somehow allow structs to implement interfaces.

I'd love it if interfaces could implement methods. (All MI related 
issues are related to state, not implementation of methods.)