Re: [perl #118053] cannot specify optional positional with Mu as default

[Moritz Lenz]

On 05/19/2013 06:41 PM, Elizabeth Mattijsen (via RT) wrote:
> # New Ticket Created by  Elizabeth Mattijsen 
> # Please include the string:  [perl #118053]
> # in the subject line of all future correspondence about this issue. 
> # <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=118053 >
> 
> 
> [18:35:53] <lizmat>    r: sub a ($a=Mu) { }; a
> [18:35:54] <+camelia>  rakudo 9c5650: OUTPUT«Nominal type check failed for 
> parameter '$a'; expected Any but got Mu instead␤  in sub a at 
> /tmp/IvMlnzFJOY:1␤  in block  at /tmp/IvMlnzFJOY:1␤␤»
> [18:36:18] <lizmat>    expected Any?  but but, I specified Mu as the default

Any is the default type constraint if you specify none; So you specify a
default that doesn't pass the type constraint, and it dies when you
don't specify a value.

If you want it to be able to receive a Mu, you have to add a type
constraint:

sub a(Mu $a = Mu) { }; a;

or simply

sub a(Mu $a?) { }; a;

So, not a bug.

Cheers,
Moritz