As we just discussed this in slack - here is an example which would cause this kind of error type:

<?php

register_shutdown_function(function() {
  var_dump(error_get_last());
});

interface Test {
    public function bla(): string;
}

class A implements Test {
    public function bla(): ?string {
        return null;
    }
}

I am fairly certain

1. Cake\Test\TestCase\Controller\Component\PaginatorComponentTest::testOutOfVeryBigPageNumberGetsClamped
   The float-string "3000000000000000000000000" is not representable as an int, cast occurred

Is actually a relevant fail in this PR.