False positives in the function forward_static_call_array

[jorgsowa]

Hello,
The following code produces two false positives

<?php

/** @return class-string */
function getClassName(object $class): string {
    return $class::class;
};

function fromArrays(array $data, object $object)
{
    $className = getClassName($object);

    return forward_static_call_array([$className, 'from'], $data);
}

https://psalm.dev/r/ecc7244555

We know that the variable passed to forward_static_call_array is a class string, so it should be treated as a callable.

ERROR: [InvalidArgument](https://psalm.dev/004) - 12:38 - Argument 1 of forward_static_call_array expects callable, but list{class-string, 'from'} provided

ERROR: [ArgumentTypeCoercion](https://psalm.dev/193) - 12:60 - Argument 2 of forward_static_call_array expects list<mixed>, but parent type array<array-key, mixed> provided

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/ecc7244555

<?php

/** @return class-string */
function getClassName(object $class): string {
    return $class::class;
};

function fromArrays(array $data, object $object)
{
    $className = getClassName($object);

    return forward_static_call_array([$className, 'from'], $data);
}

Psalm output (using commit 0e43c44):

ERROR: InvalidArgument - 12:38 - Argument 1 of forward_static_call_array expects callable, but list{class-string, 'from'} provided

ERROR: ArgumentTypeCoercion - 12:60 - Argument 2 of forward_static_call_array expects list<mixed>, but parent type array<array-key, mixed> provided

INFO: MissingReturnType - 8:10 - Method fromArrays does not have a return type

[weirdan]

We know that the variable passed to forward_static_call_array is a class string, so it should be treated as a callable.

we don't know if there's a method named from() on that class (because we don't know the class name in the first place), so we can't do that: https://3v4l.org/pb3Rr

The latter issue is a useful safeguard as lists work for every PHP version, but string-keyed arrays need to match the signature (and Psalm doesn't seem to be able to infer it): https://3v4l.org/LvpJt

[jorgsowa]

That's true, but if we pass type list{class-string, string} to function forward_static_call_array we shouldn't have any warning, because this construct creates a callable which is expected. The code is valid and in this case, the only workaround is to add the warning to baseline.

[weirdan]

because this construct creates a callable which is expected

That's the thing with callables - they are only callable if they can be called. Otherwise, they are just arrays / strings.

With that said, this should work (but doesn't): https://psalm.dev/r/a1bdbc0e6b

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/a1bdbc0e6b

<?php

/** @return class-string */
function getClassName(object $class): string {
    return $class::class;
};

/** @param list $data */
function fromArrays(array $data, object $object): mixed
{
    $className = getClassName($object);
    $callback = [$className, 'from'];
    if (!is_callable($callback)) {
		throw new RuntimeException('bad callable');
    }
    /** @psalm-trace $callback */;

    return forward_static_call_array($callback, $data);
}

Psalm output (using commit ef3b018):

INFO: Trace - 16:34 - $callback: callable-array{class-string, 'from'}

ERROR: InvalidArgument - 18:38 - Argument 1 of forward_static_call_array expects callable, but callable-array{class-string, 'from'} provided

[kkmuffme]

Isn't this code not invalid in the first place anyway, since forward_static_call_array can only be used inside a class and the code example produces a fatal? It should report an error for that.

With that said, this should work (but doesn't): https://psalm.dev/r/a1bdbc0e6b

This also produces a fatal error when run in PHP, doesn't it?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/a1bdbc0e6b

<?php

/** @return class-string */
function getClassName(object $class): string {
    return $class::class;
};

/** @param list $data */
function fromArrays(array $data, object $object): mixed
{
    $className = getClassName($object);
    $callback = [$className, 'from'];
    if (!is_callable($callback)) {
		throw new RuntimeException('bad callable');
    }
    /** @psalm-trace $callback */;

    return forward_static_call_array($callback, $data);
}

Psalm output (using commit ef3b018):

INFO: Trace - 16:34 - $callback: callable-array{class-string, 'from'}

ERROR: InvalidArgument - 18:38 - Argument 1 of forward_static_call_array expects callable, but callable-array{class-string, 'from'} provided

[weirdan]

This also produces a fatal error when run in PHP, doesn't it?

No, it works just fine: https://3v4l.org/lTQWQ

[kkmuffme]

Ah, I mixed it up with forward_static_call - that would produce a fatal. Weird thing is the PHP docs for both
https://www.php.net/manual/en/function.forward-static-call.php
https://www.php.net/manual/en/function.forward-static-call-array.php

state:

This function must be called within a method context, it can't be used outside a class.

But apparently forward_static_call_array also works outside of a class context as your example above shows?

[weirdan]

But apparently forward_static_call_array also works outside of a class context as your example above shows?

🤷‍♂️ I was confused by that passage in the docs too.