On Fri Jun 05 07:29:16 2009, jn...@jnthn.net wrote:
> On Sat Apr 25 09:23:43 2009, b...@abrij.org wrote:
> >
> > The following work as expected:
> >
> > my Num List sub f () { return ("A") };
> > my Num List sub f () { return (1) };
> > my List sub f () { return () };
> >
> > The following dies with "Type check failed on return value"
> >
> > my Num List sub f () { return () };
> >
> First, all of these should be compile time failures, since only one type
> constraint is allowed. So I've fixed Rakudo now (git 056847f) to point
> that out.
>
> I think what you really wanted to write was:
>
> my List of Num sub f() { ... }
>
> However, that's not quite supported yet in Rakudo (it will be, just not
> quite there yet), so the best we can do at the moment is:
>
> my Positional of Num sub f() { ... }
>
> If you're going to write one of these, you need to return an explicitly
> typed list. So this fails>
>
> my Positional of Num sub f() { return (1,2,3) }; f()
>
> And you need to write this:
>
> my Positional of Num sub f() { my Num @l = 1,2,3; return @l; }; f()
>
> Subtyping works too, so you can write:
>
> my Positional of Num sub f() { my Int @l = 1,2,3; return @l; }; f()
>
> But in general, if you're going to be dealing with parametric type
> constraints you need to be explicitly typing the data structures too; I
> suspect that's not going to change, at least in Perl 6.0.0.
>
> > And as an aside, type checks seem to be skipped for implicit returns:
> >
> > my Num List sub f () { ("A") }; f.say; # says "A"
> >
> Yes, that was a problem. I have fixed that too now, in the same push.
>
> Thanks,
>
> Jonathan
Oops, meant to Cc the above explanation to the list the first time.
In addition, finished fixing up completely (as far as I know it needs
fixing up) type checking of implicitly returned values. Plus added tests
to S02-builtin-datatypes/types.t for all issues in this ticket. So,
resolving.
Thanks,
Jonathan
