Multiple alias this is coming.

[IgorStepanov via Digitalmars-d-announce]

On Friday, 19 September 2014 at 18:46:14 UTC, IgorStepanov wrote:
> On Friday, 19 September 2014 at 17:19:09 UTC, Andrei 
> Alexandrescu
> wrote:
>> On 9/19/14, 3:21 AM, Dicebot wrote:
>>> On Friday, 19 September 2014 at 09:34:22 UTC, ponce wrote:
>>>> Call me unimaginative, but I'm struggling to see any use 
>>>> case for
>>>> multiple alias this, and I struggle even more for such 
>>>> constructors
>>>> aliasing.
>>>
>>> Pretty much every single time you have ever wanted to do 
>>> multiple
>>> inheritance of implementation multiple `alias this` was the 
>>> proper tool
>>> for a job. I notice myself thinking "this could have been 
>>> done much
>>> cleaner with multiple alias this" at least once a month :)
>>
>> Yah, multiple subtyping of structs is terrific to have. Thanks 
>> Igor for this work! -- Andrei
>
> You are welcome :)
> BTW. Please comment (approve or correct) semantic rules, which
> used for conflict resolving.
> I've written it early and reflected it in the PR tests.

>Further, could this also be used to somehow simplify
hierarchically defined enumerators? Typically the enumerators and
predicates related to the enumeration WordKind defined here

enum can have a class as base type:

import std.stdio;

class Word
{
      this(string type)
      {
          this.type = type;
      }

      @property abstract string wordClass();

      override size_t toHash() @trusted
      {
          string s = toString();
          return typeid(string).getHash(&s);
      }

      override string toString() @trusted nothrow
      {
          try
          {
              return wordClass() ~ ":" ~ type;
          }
          catch(Throwable th)
          {
              assert(0);
          }
      }

      string type;
}

class Noun : Word
{
      this (string type)
      {
          super(type);
      }

      @property override string wordClass()
      {
          return "noun";
      }
}

class Verb : Word
{
      this (string type)
      {
          super(type);
      }

      @property override string wordClass()
      {
          return "verb";
      }
}

enum WordKind : Word
{
      Unknown = null,
      Numeric = new Noun("Numeric"),
      //...
      Present = new Verb("Present"),
}

import std.stdio;
void main()
{
      string[][WordKind] dictionary;
      dictionary[WordKind.Numeric] ~= "one";
      dictionary[WordKind.Numeric] ~= "two";
      dictionary[WordKind.Present] ~= "go";
      writeln(dictionary);
}

Does this code can help you?