kill all backtraces, why????

gistfile1.txt

# Run any code that produces a backtrace with RAKUDO_VERBOSE_STACKFRAME=3
#
# The thinko was using $_ instead of $line - 1 as an index into @lines
# When that is done, it appears that the method is immediately exited without returning anything,
# effectively removing *any* stacktrace information.  I assume this is some vague interaction with
# the lazy list machinery / reification / whatever.

$ git diff
diff --git a/src/core/Backtrace.pm b/src/core/Backtrace.pm
index e524228..8b6af4e 100644
--- a/src/core/Backtrace.pm
+++ b/src/core/Backtrace.pm
@@ -30,7 +30,7 @@ my class Backtrace::Frame {
                 my $to   = min $!line + $extra, +@lines;
                 for $from..$to -> $line {
                     my $star = $line == $!line ?? '*' !! ' ';
-                    $text ~= "$line.fmt('%5d') $star@lines[$line - 1]\n";
+                    $text ~= "$line.fmt('%5d') $star@lines[$_]\n";
                 }
                 $text ~= "\n";
             }