From @masak

Parrot r36318 (before the merge that broke Rakudo), and Rakudo 21f374.

For some reason, creating a literal array with seven elements works,
but not eight.

$ perl6 -e 'my @​layers = [0, 0, 0, 0, 0, 0, 0]; .perl.say for @​layers'
[0, 0, 0, 0, 0, 0, 0]
$ perl6 -e 'my @​layers = [0, 0, 0, 0, 0, 0, 0, 0]; .perl.say for @​layers'
error​:imcc​:syntax error, unexpected ')' (')')
  in file 'EVAL_16' line 58
Null PMC access in isa()
[...]

From @Util

This is caused by a Parrot bug introduced in r36165, and resolved in
r36340. The example you gave exactly matches the reduced form of the
problem that I arrived at, before I traced the problem out of Rakudo and
into Parrot. See TT#​256 at https://trac.parrot.org/parrot/ticket/256 .
If you cannot update your copy of Parrot to HEAD, then you can just
apply the single line patch that resolves the problem. To get the patch,
use `svn diff -c 36340 src/pmc/resizablestringarray.pmc`. The rest of
r36340 is the regression test for the bug.

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

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