Callable should only allow public methods if used as arg in a non-$this/self context

[kkmuffme]

https://psalm.dev/r/7a6d5d9849

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/7a6d5d9849

<?php

/**
 * @param callable $arg
 * @return void
 */
function foo($arg) {
    call_user_func($arg);
}

class A {
    public function __construct() {
		foo(array($this, 'run')); // this should be an error, since it's a fatal
        $this->bar(array($this, 'run')); // this is fine
    }
    
    private function run() : void {
        echo "done";
    }

    /**
     * @param callable $arg
     * @return void
     */
    protected function bar($arg) {
        call_user_func($arg);
    }
}

$a = new A();

Psalm output (using commit ef3b018):

INFO: UnusedVariable - 30:1 - $a is never referenced or the value is not used