Incorrect inferred return type 'never'

[jack-worman]

https://psalm.dev/r/4d5cfb806a

void|never is being incorrectly reduced to never instead of void.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/4d5cfb806a

<?php

function foo(): void
{
    if (random_int(0, 1) === 1) {
        throw new \Exception();
    }
}

Psalm output (using commit 4dc969b):

INFO: LessSpecificReturnType - 3:17 - The inferred return type 'never' for foo is more specific than the declared return type 'void'

[weirdan]

/cc: @kkmuffme

[kkmuffme]

I'm unable to reproduce this locally with psalm 5.1.0 - I get "No errors found!" no matter if I try with phpdoc or with : void native type.

Maybe something in #8828 broke this? (unlikely, that was the last related thing modified which is why I'm asking)

What version is running on psalm.dev? @weirdan

[weirdan]

Currently it's ef02ded - a couple of commits behind the HEAD of master.

[kkmuffme]

@jack-worman which version do you get this error on? 5.1.0?

[jack-worman]

@kkmuffme I am on 5.1.0

[kkmuffme]

For some reason I cannot get this error on 5.1.0 with this code.
Will wait for 5.2.0 and see if I can reproduce and fix it then, as I don't have much time atm.

[kkmuffme]

I still cannot reproduce this on psalm 5.2.0

Can you confirm that you still get this error on psalm 5.2.0?

If you still get this error, can you try with my psalm config:

<psalm
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="https://getpsalm.org/schema/config"
	xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
	name="Debug"
	errorLevel="1"
	resolveFromConfigFile="false"
	phpVersion="8.1"
	cacheDirectory=".cache/psalm/dev-tests"
	findUnusedVariablesAndParams="false"
>
</psalm>

[weirdan]

@kkmuffme it requires (undocumented) restrictReturnTypes="true" attribute (Force return types to be as tight as possible on psalm.dev).

[kkmuffme]

Could this setting get documented in https://psalm.dev/docs/running_psalm/configuration/ ?
It didn't exist when I created this never check and I wasn't aware it exists until you told me.

Anyway the bug is bc of ReturnTypeCollector::getReturnTypes does not return implicit void return like in the above example, therefore creating this error (since it just returns "never" here bc of the throw, the implicit void isn't reported in $inferred_return_type_parts):
https://github.com/vimeo/psalm/blob/master/src/Psalm/Internal/Analyzer/FunctionLike/ReturnTypeAnalyzer.php#L145

I won't be able to fix this atm, but I guess it's a good first issue to modify it to check if function returns void implicitly.

[kkmuffme]

btw this is not specific to never, this happens with all other implicit void returns too:
https://psalm.dev/r/b0e397c14e
https://psalm.dev/r/6ffb302b9e

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/b0e397c14e

<?php

function foo(): void
{
    if (random_int(0, 1) === 1) {
        return false;
    }
}

Psalm output (using commit ef02ded):

ERROR: InvalidReturnStatement - 6:16 - No return values are expected for foo

INFO: LessSpecificReturnType - 3:17 - The inferred return type 'false' for foo is more specific than the declared return type 'void'

ERROR: InvalidFalsableReturnType - 3:17 - The declared return type 'void' for foo does not allow false, but 'false' contains false

https://psalm.dev/r/6ffb302b9e

<?php

function foo(): void
{
    if (random_int(0, 1) === 1) {
        return 10;
    }
}

Psalm output (using commit ef02ded):

ERROR: InvalidReturnStatement - 6:16 - No return values are expected for foo

ERROR: InvalidReturnType - 3:17 - The declared return type 'void' for foo is incorrect, got '10'

[kkmuffme]

It actually has the same issue with void + null when it's explicit too: https://psalm.dev/r/6f227ae9b9

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/6f227ae9b9

<?php

function foo(): void
{
    if (random_int(0, 1) === 1) {
        throw new \Exception();
    }
    
    return;
}

Psalm output (using commit d338b00):

INFO: LessSpecificReturnType - 3:17 - The inferred return type 'null' for foo is more specific than the declared return type 'void'