PhanUnreferencedClosure on closure directly passed to native sort functions with comparison function

[patrickallaert]

With phan 3.1.0, the following code:

<?php

$array = [
    ["x" => "xyz"],
    ["x" => "def"],
    ["x" => "abc"],
];

uasort(
    $array,
    /**
     * @param array<string,string> $a
     * @param array<string,string> $b
     */
    fn(array $a, array $b): int => $a["x"] <=> $b["x"],
);

Produces:

PhanUnreferencedClosure Possibly zero references to Closure(array $a, array $b) : int

However, the closure is used as it is passed to uasort().

[mathroc]

I’ve got a lot of @Suppress PhanUnreferencedClosure in my code base. And it seems it’s not limited to native sort functions, eg:

    public function getLastPublishedVersion(): ?Version
    {
        // @phan-suppress-next-line PhanUnreferencedClosure
        return \iter\search(static fn (Version $version): bool => $version->isPublish(), $this->versions);
    }

[umherirrender]

This is a problem with the arrow functions, because using the closures gives no warning (tested with phan5.2 online demo)

<?php

$array = [
    ["x" => "xyz"],
    ["x" => "def"],
    ["x" => "abc"],
];


uasort(
    $array,
    /**
     * @param array<string,string> $a
     * @param array<string,string> $b
     */
    function (array $a, array $b): int { return $a["x"] <=> $b["x"]; }
);