[perl #121434] [BUG] .=uniq on a hash element array in sink context wrongly leaves that array empty in Rakudo

[Carl Mäsak]

# New Ticket Created by  "Carl Mäsak" 
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<FROGGS> m: my %a; %a<foo> = <a b c>; say %a<foo>.=uniq; say %a<foo>
<camelia> rakudo-moar 5b109d: OUTPUT«a b c␤a b c␤»
<FROGGS> m: my %a; %a<foo> = <a b c>; %a<foo>.=uniq; say %a<foo>
<camelia> rakudo-moar 5b109d: OUTPUT«␤»
<FROGGS> masak: please explain the above^^
<FROGGS> why is it empty when the mutator is called in sink context?
<FROGGS> p6: my %a; %a<foo> = <a b c>; %a<foo>.=uniq; say %a<foo>
<camelia> niecza v24-109-g48a8de3: OUTPUT«a b c␤»
<camelia> ..rakudo-parrot 5b109d, rakudo-jvm 5b109d, rakudo-moar
5b109d: OUTPUT«␤»
<FROGGS> p6: my %a; %a<foo> = <a b c>; %a<foo>.=sort; say %a<foo>
<camelia> rakudo-parrot 5b109d, rakudo-jvm 5b109d, rakudo-moar 5b109d,
niecza v24-109-g48a8de3: OUTPUT«a b c␤»
<FROGGS> lizmat++ # a uniq bug!
<masak> looks like a bug to me too.
* masak submits rakudobug
<masak> r: my @a = <a b b b c c>; @a.=uniq; say @a
<camelia> rakudo-parrot 5b109d, rakudo-jvm 5b109d, rakudo-moar 5b109d:
OUTPUT«a b c␤»
<masak> innerestin'

In the case above where Niecza's behavior differs from Rakudo's,
Niecza's behavior is what I would expect.