Bitwise assignment doesn't change type

[bugreportuser]

If $x is false, using |= true should make it 1.

Example (https://getpsalm.org/r/11805c0b24):

<?php
$x = false;
$x |= rand(0, 1) !== 2;
$x |= true;
$x |= 1;
if ($x) {
    echo $x;
}

Example output:

Psalm output (using commit a428b34):

ERROR: TypeDoesNotContainType - 6:5 - Found a contradiction when evaluating $x and trying to reconcile type 'false' to !falsy

[muglug]

I've fixed this for ints - not sure about bools

[bugreportuser]

Thanks. Are you willing to add support for bools later or at least a warning?

[muglug]

Yeah, going to keep this open because it's a valid use case

[SignpostMarv]

Just checking in; is the following example a separate issue to this one? https://psalm.dev/r/222baddf7b

[bugreportuser]

@SignpostMarv It's a separate issue but similar to #2139.

[orklah]

This has been reworked since and now boolean operations with bitwise operators emits an error. Not sure we can still consider this a valid use case

[bugreportuser]

You're right. I've had to avoid this for other tools too, so this issue isn't a priority. It's surprising php hasn't started supporting bitwise operators for booleans since it would be very useful

[tvdijen]

This issue still exists, yet the error messages have changed over time;
https://psalm.dev/r/aa2d948c03

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/aa2d948c03

<?php

$enabled = false;
$classes = ['SomeClass', 'SomeOtherClass'];
foreach ($classes as $class) {
    $enabled |= class_exists($class);
}

return $enabled;

Psalm output (using commit 3fcfc94):

ERROR: PossiblyFalseOperand - 6:5 - Left operand cannot be falsable, got false|float|int

ERROR: InvalidOperand - 6:17 - Cannot perform a numeric operation with a non-numeric type bool

[AndrolGenhald]

I went and implemented this with the strictBooleanOperands config, but then I decided it's a really bad idea and scrapped it.

I figured for consistency we should support all the boolean operators:

$bool = random_int(0, 1) ? true : false;

/** @psalm-check-type-exact $var = 1|2 */
$var = $bool + 1;
/** @psalm-check-type-exact $var = -1|-2 */
$var = $bool - 2;
/** @psalm-check-type-exact $var = 0|1 */
$var = $bool % 3;
/** @psalm-check-type-exact $var = 0|2 */
$var = $bool * 2;
/** @psalm-check-type-exact $var = 0|1 */
$var = $bool ** 3;
/** @psalm-check-type-exact $var = 4|5 */
$var = $bool | 4;
/** @psalm-check-type-exact $var = 2|3 */
$var = $bool ^ 3;
/** @psalm-check-type-exact $var = 0|1 */
$var = $bool & 3;
/** @psalm-check-type-exact $var = 0|4 */
$var = $bool << 2;
/** @psalm-check-type-exact $var = 0|1 */
$var = $bool >> 0;

But if we do that, then this doesn't show any issues:

/** @var string */
$str = "some string";
$pos = strpos($str, "z") + 1;

And I think catching that is more important than allowing |= on booleans. I think the real solution here is for PHP to add logical assignment operators &&= and ||= (ie someone should pick up php/php-src#4535), but until then I think casting is the way to go.

Should we go ahead and close this @orklah?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/daa21fb9b5

<?php

/** @var string */
$str = "some string";
$pos = strpos($str, "z") + 1;

Psalm output (using commit 2d83a4b):

ERROR: PossiblyFalseOperand - 5:8 - Left operand cannot be falsable, got false|int<0, max>

https://psalm.dev/r/bdb02a1b35

<?php
$x = (int) false;
$x |= (int) true;
$x |= 1;
$x &= (int) (rand(0, 1) !== 1);
if ($x) {
  echo $x;
}

Psalm output (using commit 2d83a4b):

No issues!

[orklah]

I'm not sure why solving boolean operations make the strpos operation go without Issue, can you explain that?

[AndrolGenhald]

I pushed my attempt here so you can look at it. The problem is that the bool to int cast happens before the PossiblyFalseOperand is emitted. I hadn't considered to try both allowing the cast and emitting the issue, but I thought the point was more to make Psalm allow this pattern without any issues rather than to still show issues but have the correct types.

Especially after the casting improvements in #7696 I think the best solution for now is just for users to cast when doing this, it will result in correct types and no issues from Psalm.