sequence for custom class

seq_cmp.p6

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 };

my $a = A.new( val => 3 );
my $b = A.new( val => 4 );

say 'Sequence 1: ($a ... 6)[^5]';
say ($a ... 6)[^5];
say "";

say 'Sequence 2: ($a, $b ... 6)[^5]';
say ($a, $b ... 6)[^5];
say "";

say $a cmp 6;
say $a.Stringy cmp 6.Stringy;

$ perl6-m seq_cmp.p6 
Sequence 1: ($a ... 6)[^5]
DEBUG: method pred was called
DEBUG: method pred was called
DEBUG: method pred was called
DEBUG: method pred was called
A.new(val => 3) A.new(val => 2) A.new(val => 1) A.new(val => 0) A.new(val => -1)

Sequence 2: ($a, $b ... 6)[^5]
DEBUG: method succ was called
DEBUG: method succ was called
A.new(val => 3) A.new(val => 4) A.new(val => 5) A.new(val => 6)

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I'm trying to generate a sequence with a custom class A. On MoarVM sequence 2 works as expected, but for sequence 1 (only $a given on the LHS) the sequence goes "downwards". S03 states:

For functions deduced when there is only one value on the left, the final value is used to determine whether *.succ or *.pred is more appropriate. The two values are compared with cmp to determine the direction of the progression.

Note: If I use $a, *.succ ... 6 I get the expected result.

On JVM sequence 1 also is generated by calling 'pred'. Interestingly for sequence 2 I see flapping behaviour: Most times I get A.new(val => 3) A.new(val => 4) A.new(val => 3) A.new(val => 2) A.new(val => 1) but sometimes I get A.new(val => 3) A.new(val => 4) A.new(val => 5) A.new(val => 6).

I tried to define a matching multi candidate for infix:<cmp>. It doesn't seem to work, though: If I comment it out I get the same results (except for the second to last 'say' command, of course).

It looks to me as if the supplied multi candidate is not "visible" within sub SEQUENCE from src/core/operators.pm and this routine instead calls the multi candidate multi sub infix:<cmp>(\a, \b) from src/core/Order.pm which calls Stringy an both elements and does a cmp with those values.