InvalidArgument vs PossiblyFalseArgument

[gdejong]

A method expecting a string, but passed true outputs an InvalidArgument:

https://psalm.dev/r/47caf98787

Same thing, but now passed false outputs a PossiblyFalseArgument:

https://psalm.dev/r/0b9b837d1d

In this case false is not "possibly" false, it definitely is false.

Is this intentional behavior or a bug?

(I would have expected an InvalidArgument error in the second case as well)

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/47caf98787

<?php
declare(strict_types=1);

function takesAString(string $s): void{
  echo $s;   
}

takesAString(true);

Psalm output (using commit d82f028):

ERROR: InvalidArgument - 8:14 - Argument 1 of takesAString expects string, true provided

https://psalm.dev/r/0b9b837d1d

<?php
declare(strict_types=1);

function takesAString(string $s): void{
  echo $s;   
}

takesAString(false);

Psalm output (using commit d82f028):

ERROR: PossiblyFalseArgument - 8:14 - Argument 1 of takesAString cannot be false, possibly false value provided

[weirdan]

It is intentional, although it could be clearer. The reason is that many internal functions return false in error scenarios, although it's often desired to ignore that. So having a separate issue lets you ignore specifically that. There's also PossiblyNullArgument, for the same reason.

[orklah]

Shouldn't the false case be handled by the @ignore-falsable-return flag instead and be declared as a real InvalidArgument when it's not? In this case, a literal should definitely reported as the biggest error level possible