[perl #114394] [BUG] Type capture in signatures captures the wrong thing when rw containers are passed to a routine in Rakudo

[Carl Mäsak]

# New Ticket Created by  "Carl Mäsak" 
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# <URL: https://rt.perl.org:443/rt3/Ticket/Display.html?id=114394 >


<nebuchadnezzar> hi
<nebuchadnezzar> looking at perl6 book, I tried the examples and find
something curious: http://pastebin.com/v835G1MD
<nebuchadnezzar> "given" in the sub does not seems to behave the same
way as outside
* masak is looking into it now
<masak> reproduced the bug locally.
<masak> golfing.
<masak> r: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 };
sub p($a, $b) { w $a, $b }; say p(R, R); say w(R, R)
<p6eval> ..rakudo 7e1b38: OUTPUT«-1␤0␤»
* masak submits rakudobug
<masak> r: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 };
(-> $a, $b { say w $a, $b })(R, R); say w R, R
<p6eval> rakudo 7e1b38: OUTPUT«-1␤0␤»
<masak> correction: the parameter binding is messing it up somehow.
<jnthn> masak: Was the issue there with star?
<masak> star: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 };
(-> $a, $b { say w $a, $b })(R, R); say w R, R
<p6eval> star 2012.07: OUTPUT«-1␤0␤»
<masak> yep.
<jnthn> OK, not a qast related regression then.
<masak> r: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 }; my
($a, $b) = (-> $a, $b { $a, $b })(R, R); say w $a, $b
<p6eval> rakudo 7e1b38: OUTPUT«-1␤»
<masak> curiouser and curiouser.
<masak> r: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 }; my
($a, $b) = R, R; say w $a, $b
<p6eval> rakudo 7e1b38: OUTPUT«-1␤»
<masak> a-ha!
<masak> not parameter binding. variables!
<masak> containers, most like.
<masak> r: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 }; my
@x = R, R; say w(|@x)
<p6eval> rakudo 7e1b38: OUTPUT«-1␤»
<masak> aye.
<jnthn> Hm
<jnthn> Can you make it happen without type catpures?
<jnthn> Or are they a necesary part of it?
<masak> I have a hunch they are.
<masak> r: class R {}; multi w(R, R) { 0 }; multi w($, $) { -1 }; my
@x = R, R; say w(|@x)
<p6eval> rakudo 7e1b38: OUTPUT«0␤»
<masak> aye. they are part of it.
<masak> r: class R {}; multi w(::T, T) { 0 }; multi w($, $) { -1 };
say w(|[R, R])
<p6eval> rakudo 7e1b38: OUTPUT«-1␤»
<masak> r: multi w(::T, T) { 0 }; multi w($, $) { -1 }; say w(|[1, 1])
<p6eval> rakudo 7e1b38: OUTPUT«-1␤»
<masak> r: multi w(::T, T) { 0 }; multi w($, $) { -1 }; say w(1, 1)
<p6eval> rakudo 7e1b38: OUTPUT«0␤»
* masak loves golfin' :)
<masak> r: sub w(::T, T) { 0 }; say w(|[1, 1])
<p6eval> rakudo 7e1b38: OUTPUT«Nominal type check failed for parameter
''; expected Scalar but got Int instead␤  in sub w [...]
<masak> yay, I tricked Rakudo into telling me what's wrong, even!
<jnthn> masak++ # that makes it rather clearer
* masak does a victory dance