Integer overflow

The Raku program below does not recognize a signed integer overflow and the program continues with wrong results.

my int64 ($a, $b, $c) = 9223372036854775807, 5000000000000000000, 3037000500;
.say for -(-$a - 1), $b + $b, -$a - $a, $c * $c, (-$a - 1)/-1;

Output:

-9223372036854775808
-8446744073709551616
2
-9223372036709301616
9223372036854775808