===description===
callableMissingOptionalVariableInstanceArray
===file===
<?php
                    /**
                     * @param callable(string=):bool $arg
                     * @return void
                     */
                    function foo($arg) {}

                    class A {
                        public function bar(): bool {
                            return true;
                        }
                    }

                    $a_instance = new A();
                    $y = [$a_instance, "bar"];
                    foo($y);
===expect===
PossiblyInvalidArgument
===ignore===
TODO
