usev6

class A {
    has $.val;
    method Numeric { $.val };
    method succ { say "DEBUG: method succ was called"; A.new( val => $.val+1) };
    method pred { say "DEBUG: method pred was called"; A.new( val => $.val-1) };
}

multi sub infix:<cmp> (A $x, Int $n) { $x.val cmp $n };
multi sub infix:<cmp> (A $x, A $y) { $x.val cmp $y.val };

usev6

$ perl6-j --ll-exception -e '"a" ~~ /"$0"/'
Cannot unbox a type object
  in warn (gen/jvm/CORE.setting:811)
  in warn (gen/jvm/CORE.setting:807)
  in Str (gen/jvm/CORE.setting:1212)
  in Str (gen/jvm/CORE.setting:1208)
  in Stringy (gen/jvm/CORE.setting:1222)
  in Stringy (gen/jvm/CORE.setting:1219)
  in infix:<~> (gen/jvm/CORE.setting:1649)
  in infix:<~> (gen/jvm/CORE.setting:1647)

usev6

$ perl6-j -e 'say "a" ~~ /"$0"/'
{:file("gen/jvm/CORE.setting"), :line(9411)}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>
{:file("gen/jvm/CORE.setting")}<>

usev6

diff --git a/src/core/Block.pm b/src/core/Block.pm
index 8e78e82..dbf937e 100644
--- a/src/core/Block.pm
+++ b/src/core/Block.pm
@@ -36,6 +36,7 @@ my class Block { # declared in BOOTSTRAP
     }
 
     method assuming(Block:D $b: |curried) {
+        1;
         anon sub CURRIED (|direct) {

usev6

$ viv -e 'my @foo; my $exists = @foo[0]:exists;'
VAST::comp_unit, BEG: 0, END: 38
│ └─LEX: !!perl/hash:Stash
│        '!file': &1
│          name: (eval)
│        '!id': &2
│        - MY:file<(eval)>
│        '!line': 0
│        $!: !!perl/hash:NAME
│          dynamic: 1

usev6

diff --git a/src/core/Str.pm b/src/core/Str.pm
index 4b9fdb0..5cf4dcd 100644
--- a/src/core/Str.pm
+++ b/src/core/Str.pm
@@ -907,7 +907,7 @@ my class Str does Stringy { # declared in BOOTSTRAP
                             $!todo = $!todo - 1;
                             my int $found = nqp::index($!string,$!match,$!pos);
                             $found < 0
-                              ?? $!todo = 0
+                              ?? ($!todo = 0)

usev6

Stage parse      : Error while constructing error object:Could not locate compile-time value for symbol X::Syntax::ConditionalOperator::PrecedenceTooLoose
Error while compiling, type X::Syntax::ConditionalOperator::PrecedenceTooLoose
  operator: =
 at line 9861, near "?? $!todo "
  in panic (gen/jvm/stage2/NQPHLL.nqp:399)
  in typed_exception (src/Perl6/World.nqp:3812)
  in throw (src/Perl6/World.nqp:3623)
  in typed_panic (src/Perl6/Grammar.nqp:240)
  in infix:sym<?? !!> (src/Perl6/Grammar.nqp:4194)
  in !protoregex (gen/jvm/stage2/QRegex.nqp:1350)

usev6

diff --git a/src/core/Failure.pm b/src/core/Failure.pm
index 70aa7be..4a7baff 100644
--- a/src/core/Failure.pm
+++ b/src/core/Failure.pm
@@ -56,7 +56,7 @@ my class Failure {
     multi method Str(Failure:D:)  { $!handled ?? $.mess !! self!throw(); }
     multi method gist(Failure:D:) { $!handled ?? $.mess !! self!throw(); }
     method mess (Failure:D:) {
-        "(HANDLED) " x $!handled ~ self.exception.message ~ "\n" ~ self.backtrace;
+        "(HANDLED) " x ($!handled ?? $!handled !! 0) ~ self.exception.message ~ "\n" ~ self.backtrace;

usev6

With the following changes I'm able to build rakudo.jvm on commit a2a34c26

The code I had to work around was modified by these three commits
* 5349d05c
* ad08a1d7
* cc4d72c4

$ git diff
diff --git a/src/core/Failure.pm b/src/core/Failure.pm
index 76ad01f..6d45344 100644

usev6

use nqp;

my \iter = (3,2,1,4).iterator;
my \sort-buffer = IterationBuffer.new;
unless iter.push-until-lazy(sort-buffer) =:= IterationEnd {
    fail X::Cannot::Lazy.new(:action<sort>);
}       

my int $i = 0;
my int $n = sort-buffer.elems;