Jonathan (>), Carl (>>):
> > This might be in RT already, but I didn't find it, so...
> >
> > <ihrd> rakudo: multi foo (@a) { 1 }; multi foo ($a, %h?) { 2 }; say
> > foo(<1 2 3>);
> > <p6eval> rakudo 69b318: OUTPUT«Ambiguous dispatch to multi 'foo'.
> > Ambiguous candidates had signatures::(Positional.new() @a):(Any $a,
> > Associative.new() %h?) [...]
> > * masak submits rakudobug
> >
> > As for arity, both methods can match. But the first candidate has a
> > type constraint Positional on its first parameter, so it should be
> > narrower than the second one, which doesn't.
> It's not so clear cut that this is a bug. Positional is a role, and is
> done by some things (like List, Array, etc), but doesn't have a
> relationship with Any in any way. The default parameter type is Any.
> Thus if you try Positional ~~ Any, you'll get false (and vice versa -
> they are tied types so far as the dispatcher is concerned).
>
> Anyway, the dispatcher is behaving as I would have expected in terms of
> considering those candidates tied. I do agree it isn't very dwim-y, but
> nothing occurs to me right away that we could do in order to make it
> dwim more...
I see. In short, there's a tie because Positional isn't narrower than
Any. I get it now, and agree on a formal level.
...the problem is just that the sigils '@' and '%' _feel_ like they
should be narrower than '$', because the latter can contain anything.
The question is probably whether it's possible to reflect that intuition
in the MMDer without breaking something important.
