Is there any chance to introduce concepts/traits/typeClasses in dlang?

[mipri]

On Sunday, 15 December 2019 at 16:11:31 UTC, sighoya wrote:
> TypeClasses aren't a static solution only, they can also be
> used as existentials allowing dynamic dispatch
...
> A possible look how flexible it can be taken from the nim
> language
> Link:
> https://nim-lang.org/docs/manual_experimental.html#concepts

 From that page:

   The concept is a match if:
   - all of the expressions within the body can be compiled for 
the tested type
   - all statically evaluable boolean expressions in the body must 
be true

Looks to me like this is just a way of attaching D's static
constraints to a type, so that

   void push(T)(Stack!T stack, T item) { }

becomes (something like, for inference's sake S shouldn't be
separate I think):

   void push(S,T)(S!T stack, T item) if (a bunch of !S tests) { }

What does this have to do with dynamic dispatch? How is this
not already something you can do with an isStack!S test?

> Nevertheless, we can't changed everything in a 
> backward-compatible way. I hope some of you are happy to 
> discuss ideas about concepts in this thread.

I don't understand what you're trying to do, and these A, B, C,
D examples take a lot effort to read, vs. Comparable and Stack
examples.

What I'd prefer is

   // valid current-D example:

   ...

   // but look at (how verbose this is | how expensive this is |
   // how much effort it'd take to adapt this in Y direction |
   // &c)!

vs.

   // valid improved-D example: