first element of $indices is (Any) here

gistfile1.txt

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;
my $transform = False;

say $n;

my $indices := nqp::list;
nqp::setelems($indices,$n);
nqp::bindpos($indices,$i,nqp::decont($i)) while ++$i < $n;

say $indices;