Reverted for JVM in d9b19da , but I think this warrants further research.:
> On 11 May 2016, at 07:44, Christian Bartolomaeus (via RT)
> <perl6-bugs-follo...@perl.org> wrote:
>
> # New Ticket Created by Christian Bartolomaeus
> # Please include the string: [perl #128123]
> # in the subject line of all future correspondence about this issue.
> # <URL: https://rt.perl.org/Ticket/Display.html?id=128123 >
>
>
> The following code from S03-metaops/hyper.t dies on rakudo-j:
>
> $ perl6-j -e '[[2, 3], [4, [5, 6]]]».combinations.gist'
> Expected a native int argument for '$a'
> <Internal error while creating backtrace: Expected a native int argument for
> '$a' in sub prefix:<++> at gen/jvm/CORE.setting line 8630
> in method next-interesting-index at gen/jvm/CORE.setting line 20779
> in block at gen/jvm/CORE.setting line 20829
> in method nice at gen/jvm/CORE.setting line 20827
> in method Str at gen/jvm/CORE.setting line 20860
> in method Stringy at gen/jvm/CORE.setting line 1117
> in sub infix:<~> at gen/jvm/CORE.setting line 1597
> in block at gen/jvm/CORE.setting line 30498
> in code at gen/jvm/CORE.setting line 20959
> in block at gen/jvm/CORE.setting line 20959
> in method gist at gen/jvm/CORE.setting line 20953
> in block at gen/jvm/CORE.setting line 21232
> in sub print_exception at gen/jvm/CORE.setting line 21225
> .
> Please report this as a bug (mail to rakudo...@perl.org)
> and re-run with the --ll-exception command line option
> to get more information about your error>
>
> Output with --ll-exception:
>
> $ perl6-j --ll-exception -e '[[2, 3], [4, [5, 6]]]».combinations.gist'
> Expected a native int argument for '$a'
> in prefix:<++> (gen/jvm/CORE.setting:8630)
> in prefix:<++> (gen/jvm/CORE.setting:2080)
> in (gen/jvm/CORE.setting:14728)
> in pull-one (gen/jvm/CORE.setting:4101)
> in push-all (gen/jvm/CORE.setting:2390)
> in push-until-lazy (gen/jvm/CORE.setting:2402)
> in reify-until-lazy (gen/jvm/CORE.setting:14278)
> in join (gen/jvm/CORE.setting:15014)
> in join (gen/jvm/CORE.setting:1800)
> in (gen/jvm/CORE.setting:14727)
> in (gen/jvm/CORE.setting:1137)
> in (gen/jvm/CORE.setting:1133)
> in gistseen (gen/jvm/CORE.setting:1127)
> in gist (gen/jvm/CORE.setting:14726)
> in gist (gen/jvm/CORE.setting:1151)
> in gist (gen/jvm/CORE.setting:12791)
> in gist (gen/jvm/CORE.setting:1151)
> in (gen/jvm/CORE.setting:14731)
> in (gen/jvm/CORE.setting:14731)
> in (gen/jvm/CORE.setting:14728)
> in pull-one (gen/jvm/CORE.setting:4101)
> in push-all (gen/jvm/CORE.setting:2390)
> in push-until-lazy (gen/jvm/CORE.setting:2402)
> in reify-until-lazy (gen/jvm/CORE.setting:14278)
> in join (gen/jvm/CORE.setting:15014)
> in join (gen/jvm/CORE.setting:1800)
> in (gen/jvm/CORE.setting:14727)
> in (gen/jvm/CORE.setting:1137)
> in (gen/jvm/CORE.setting:1133)
> in gistseen (gen/jvm/CORE.setting:1127)
> in (gen/jvm/CORE.setting:1147)
> in gistseen (gen/jvm/CORE.setting:1127)
> in gist (gen/jvm/CORE.setting:14726)
> in gist (gen/jvm/CORE.setting:1151)
> in <unit> (-e:1)
> in <unit-outer> (-e:1)
> in eval (gen/jvm/stage2/NQPHLL.nqp:1198)
> in eval (src/Perl6/Compiler.nqp:161)
> in (gen/jvm/stage2/NQPHLL.nqp:1288)
> in command_eval (gen/jvm/stage2/NQPHLL.nqp:1285)
> in command_eval (src/Perl6/Compiler.nqp:29)
> in command_line (gen/jvm/stage2/NQPHLL.nqp:1269)
> in MAIN (gen/jvm/main.nqp:37)
> in <mainline> (gen/jvm/main.nqp:33)
> in (gen/jvm/main.nqp)
>
> I did a bisect and it breaks with commit
> https://github.com/rakudo/rakudo/commit/b5c041a6ca -- namely the changes to
> lines 45 and 46 (changing postfix:<++> to prefix:<++> cause the error.