[perl #110038] [BUG] ().pick returns empty list and ().roll returns Nil in Rakudo -- one of them is wrong

[Carl Mäsak]

# New Ticket Created by  "Carl Mäsak" 
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<moritz> nom: say ().pick.defined
<p6eval> nom 33fb02: OUTPUT«True␤»
<moritz> nom: say ().pick.perl
<p6eval> nom 33fb02: OUTPUT«().list␤»
<moritz> uhm
<moritz> shouldn't that return something like Nil?
<moritz> niecza: say ().pick.perl
<p6eval> niecza v14-20-g18249a6: OUTPUT«Any␤»
<moritz> or that
<masak> I think I can make a stronger case for Nil than for Any.
<masak> but it depends on how much a special case .pick() is compared
to .pick($n).
<moritz> perl6: say (1, 2).pick(3).perl
<p6eval> rakudo 33fb02, niecza v14-20-g18249a6: OUTPUT«(2, 1).list␤»
<p6eval> ..pugs b927740: OUTPUT«(1, 2)␤»
<moritz> perl6: say ().roll.perl
<p6eval> niecza v14-20-g18249a6: OUTPUT«Any␤»
<p6eval> ..rakudo 33fb02: OUTPUT«Nil␤»
<masak> nom: say ().pick.defined; say ().roll.defined
<p6eval> nom 33fb02: OUTPUT«True␤False␤»
<masak> yeah. not kosher.
* masak submits rakuodbug

Clearly, something is underspecified/incorrect in all this. .pick and
.roll should behave the same on empty lists, and there should be a
good rationale for what it returns.

Here's what S02 has to say about Nil:

    There is a special C<Parcel> value named C<Nil>.  It means "there
    is no value here".  It is the undefined equivalent of the empty
    C<()> list, except that the latter is defined and means "there are
    0 arguments here".

So Nil sounds like a fine candidate for ().pick to return, in the
sense that calling .pick indicates the expectation to get a value
back, but there is no value there.