From @masak

<tadzik> rakudo​: my $a = 1, 2, 3; $a = $a.grep({1}); say $a.perl
<p6eval> rakudo 72d158​: OUTPUT«Cannot resume dead coroutine. [...]
* masak submits rakudobug
<masak> tadzik++
<masak> rakudo​: my $a = $a.grep(True); say $a.perl
<p6eval> rakudo 72d158​: OUTPUT«Cannot resume dead coroutine. [...]
<thou> weird that this hasn't shown up before [20​:54]
<masak> assignments with the same container in both the lhs and rhs
being problematic has shown up before.
<masak> but the case I'm thinking of was about hashes.
<masak> ah; that's http://rt.perl.org/rt3//Public/Bug/Display.html?id=77586

From @moritz

Works now, with tests in S03-operators/assign.t

@moritz - Status changed from 'new' to 'resolved'