PossiblyNullValue is incorrect for boolean casts

[danielbeardsley]

If $y is nullable, an "if" on a bool cast should be enough. These should be safe:

if ((bool)$y) $y->getOffset();
OR
assert((bool)$y) && $y->getOffset();

But psalm doesn't think they are. But it thinks doing the same with !! is safe:

if (!!$y) $y->getOffset();
OR
assert(!!$y) && $y->getOffset();

I'm pretty sure these are all safe and produce the same results.

Demo:
https://psalm.dev/r/0786d225c2

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/0786d225c2

<?php

function check(DateTime $i = null, DateTime $y = null): void {
	if (!!$i) $i->getOffset();
	if ($y) $y->getOffset();
    if ((bool)$y) $y->getOffset();
	assert(!!$i) && $i->getOffset();
	assert((bool)$y) && $y->getOffset();
}

check();

Psalm output (using commit 5db75df):

ERROR: PossiblyNullReference - 6:23 - Cannot call method getOffset on possibly null value

ERROR: PossiblyNullReference - 8:26 - Cannot call method getOffset on possibly null value

[muglug]

FYI if ((bool) $foo) is very unnecessary

[danielbeardsley]

is very unnecessary

100% agree. I was just highlighting other permutations of the problem.

I discovered this when using assert((bool)$x); to protect some code from a possibly-null error.