psalm/docs/running_psalm/issues/ImplicitToStringCast.md

ImplicitToStringCast

Emitted when implicitly converting an object with a __toString method to a string

<?php

class A {
    public function __toString() {
        return "foo";
    }
}

function takesString(string $s) : void {}

takesString(new A);

How to fix

You can add an explicit string cast:

<?php

...

takesString((string) new A);