Covariant Return Types
Covariant Returns and Contravariant Parameters — Levi Morrison
https://wiki.php.net/rfc/covariant-returns-and-contravariant-parameters —
typed properties are invariant
<?php
class 🍞bread {}
class 🥖baguette extends 🍞bread {}
class Bakery
{
public function gimme(): 🥖baguette {}
}
class Patisserie extends Bakery
{
public function gimme(): 🍞bread {}
}
?>
Fatal error: Declaration of Patisserie::gimme(): 🍞bread must be compatible with Bakery::gimme(): 🥖baguette
Return types are *co-variant*:
~they can *not* return a wider type~