DIP66 - Multiple alias this

[Steven Schveighoffer]

On 9/30/20 12:12 AM, H. S. Teoh wrote:
> On Wed, Sep 30, 2020 at 02:34:27AM +0000, Mike via Digitalmars-d wrote:
>> On Wednesday, 30 September 2020 at 02:08:17 UTC, Andrei Alexandrescu wrote:
> [...]
>>> I'd love it if interfaces could implement methods. (All MI related
>>> issues are related to state, not implementation of methods.)
>>
>> FWIW, C# 8 recently added such a feature.  They call it "Default
>> Interface Members":
>> https://devblogs.microsoft.com/dotnet/default-implementations-in-interfaces/
>> However, the didn't finish the implementation and deferred this very
>> important component:  https://github.com/dotnet/csharplang/issues/2337
>> I've used this feature quite a bit, but it's only mildly useful until
>> #2337 is addressed.
> 
> Don't we already have this in D?
> 
> 	interface I {
> 		void method1();	// overridable method
> 		final void method2() {} // default method
> 	}
> 	class C : I {
> 		void method1() {}
> 	}
> 
> Of course, currently method bodies in interfaces are only allowed when
> it's final.  This may or may not correspond with what C# does.

It looks like default method bodies are virtual and can be overridden.

I sort of remember at least having discussions about doing something 
like this, but I don't think it ever happened.

-Steve