Several instanceof instances need to be treated as a union type (or, better, an intersection type)

[YuriyNasretdinov]

Code Example

<?php
class A { public function c() { return 1; } }
class B { public function c() { return 2; } }

function test($a) {
if ($a instanceof A || $a instanceof B) {
 echo $a->c();
}
}

Actual Behavior

Call to undefined method {mixed}->c();

Expected Behavior

No errors.

[i582]

Done by #1058