in src/ExpectObj.hack [324:332]
public function toHaveSameContentAs<Tk as arraykey>(
KeyedContainer<Tk, mixed> $expected,
string $msg = '',
mixed ...$args
): void {
$msg = \vsprintf($msg, $args);
$value = $this->var;
$this->assertContentsEqual($expected, $value as Traversable<_>, $msg);
}