Nil is always a valid return value regardless of any check.
This is because it is the base of all failures.
On Sat, Dec 19, 2020, 8:17 PM yary <not....@gmail.com> wrote:
> Is this a known issue, or my misunderstanding?
>
> > subset non-Nil where * !=== Nil;
> (non-Nil)
> > sub out-check($out) returns non-Nil { return $out }
> &out-check
> > out-check(44)
> 44
> > out-check(Nil)
> Nil
>
> ^ Huh, I expected an exception on "out-check(Nil)" saying the return value
> failed the "returns" constraint.
>
> The subtype works as I expect as an the argument check
>
> > sub in-check (non-Nil $in) { $in }
> &in-check
> > in-check(33)
> 33
> > in-check(Nil)
> Constraint type check failed in binding to parameter '$in'; expected
> non-Nil but got Nil (Nil)
> in sub in-check at <unknown file> line 1
> in block <unit> at <unknown file> line 1
>
> $ raku --version
> This is Rakudo version 2020.07 built on MoarVM version 2020.07
> implementing Raku 6.d.
>
> Is this my understanding of return type checking that's off, or a known
> issue, or something I should add to an issue tracker?
>
> -y
>
