Strange array<empty, empty> type inference

[someniatko]

https://psalm.dev/r/cf250aab5b

$res should be array{1, 2}|array<empty, empty> or like that.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/cf250aab5b

<?php

/** @template T */
class Option
{
    /** @param T $v */
    public function __construct(private $v) {}
    
    /**
     * @template E
     * @param E $else
     * @return T|E
     */
    public function getOrElse($else)
    {
       return random_int(0, 1) === 1 ? $this->v : $else; 
    }
}

$opt = new Option([1, 2]);
/** @psalm-trace $opt */

$res = $opt->getOrElse([]);
/** @psalm-trace $res */

Psalm output (using commit f62b83a):

INFO: Trace - 23:1 - $opt: Option<array{1, 2}>

INFO: Trace - 24:25 - $res: array<empty, empty>

INFO: UnusedVariable - 23:1 - $res is never referenced or the value is not used

[orklah]

Interestingly, this doesn't happen with standard ternaries for example
https://psalm.dev/r/d05df407f7

Nor when the templates are from the same method:
https://psalm.dev/r/d811b083c3 (although the result is not perfect either here)

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/d05df407f7

<?php

$c = rand(0,1) ? [1, 2] : [];
/** @psalm-trace $c */;

Psalm output (using commit e89f7e3):

INFO: Trace - 4:23 - $c: array{0?: 1, 1?: 2}

INFO: UnusedVariable - 3:1 - $c is never referenced or the value is not used

https://psalm.dev/r/d811b083c3

<?php

/**
 * @template T of array
 * @template E of array
 * @param E $else
 * @param T $if
 * @return T|E
 */
function getOrElse($if, $else)
{
    return rand(0, 1) ? $if : $else;
}


$opt = getOrElse([], [1, 2]);
/** @psalm-trace $opt */

Psalm output (using commit e89f7e3):

INFO: Trace - 17:25 - $opt: array{1, 2}

INFO: UnusedVariable - 16:1 - $opt is never referenced or the value is not used

[orklah]

Great, my case was fixed too! Thanks!