From @coke

This test from integration/advent2010-day19.t works on moar, but not on the JVM.

16​:33 < [Coke]> r​: my $value = 42 but False; say ?$value;
16​:33 <+camelia> rakudo-jvm 3cc195​: ( no output )
16​:33 <+camelia> ..rakudo-moar 3cc195​: OUTPUT«False␤»

--
Will "Coke" Coleda

From @peschwa

On Thu Oct 29 13​:35​:04 2015, coke wrote​:

This test from integration/advent2010-day19.t works on moar, but not
on the JVM.

16​:33 < [Coke]> r​: my $value = 42 but False; say ?$value;
16​:33 <+camelia> rakudo-jvm 3cc195​: ( no output )
16​:33 <+camelia> ..rakudo-moar 3cc195​: OUTPUT«False␤»

http://irclog.perlgeek.de/p6dev/2016-04-07#i_12299830 has my findings regarding this bug. Unfortunately nothing that points towards a fix, but at least some digging regarding what's happening.

The RT System itself - Status changed from 'new' to 'open'

From @usev6

For the records​: This works with '--optimize=off' (as psch++ has shown in the linked discussion on #perl6).

$ ./perl6-j --optimize=off -e 'my $value = 42 but False; say ?$value'
False

The optimizer adds a QAST​::Want for the mixin which the JVM backend does not handle correctly.

$ RAKUDO_OPTIMIZER_DEBUG=1 ./perl6-j -e 'my $value = 42 but False; say ?$value'
[...]
  - QAST​::Want <>
  - QAST​::WVal(Int+{<anon|1285927979>}) <>
  - Ii
  - QAST​::IVal(42) <>
[...]
True

See also my findings in https://rt-archive.perl.org/perl6/Ticket/Display.html?id=129782 which is about a similar problem.

From @usev6

Fixed with Raku/nqp@2d88d98201

I'm closing this ticket as 'resolved'.

@usev6 - Status changed from 'open' to 'resolved'