Why no multiple-dispatch?

[via Digitalmars-d-learn]

On Monday, 25 August 2014 at 17:16:10 UTC, Idan Arye wrote:
>  * Alternative implementations need to implement them(even 
> though the frontend is shared, there can always be some 
> complications(plus I think mutli-methods might need some 
> backend modifications as well, thhoguh I'm no expert on that 
> matter))
>
>  * Risking regressions - changing the code will never be as 
> orthogonal as changing the data it works on...
>
> The point is that the usefulness of multi-methods, and the 
> inconvenience of having as a library solution are not nearly 
> big enough to pay that price.

If we assume just double-dispatch over class-types and that you 
instantiate all functions first. Couldn't you then have this:

eat(virtual BaseBeing v, virtual BaseFood f,float amount){}
eat(virtual Human v, virtual Fruit f,float amount){]
eat(virtual Human v, virtual Stone f,float amount){}
eat(virtual Monster v, virtual Corpse f,float amount){}
eat(virtual Human v, virtual Corpse f,float amount){}

Then extend the typeinfo of classes in the first param with a 
minimal typeid and 2D table that lists all combinations that the 
"custom linker" can find based on the mangling?

Or maybe there are some hidden traps…