Bug #75590 [Opn->Nab]: Fatal error when removing optional argument in subclass (BC break).
Edit report at https://bugs.php.net/bug.php?id=75590&edit=1
ID: 75590
Updated by: pollita@php.net
Reported by: christoph at burschka dot de
Summary: Fatal error when removing optional argument in
subclass (BC break).
-Status: Open
+Status: Not a bug
Type: Bug
Package: *General Issues
Operating System: MacOS
PHP Version: 7.2.0RC6
Block user comment: N
Private report: N
New Comment:
The fact that PHP < 7.2 accepted this was an unintentional side-effect. The code you present
doesn't follow valid inheritance contract.
Consider:
function foo(B $b) {
$b->f(new A);
}
That code *should* always work, because B::f() declares a contract by which it accepts an instance
of A as an argument, and therefore all children of B must adhere to that contract. However, the
following will fail, even in 7.1
foo(new C);
Because while C is a valid instance of B and will pass the type check, C::f() does not accept
arguments and thus violates its parent's contract.
Previous Comments:
------------------------------------------------------------------------
[2017-11-29 17:08:53] christoph at burschka dot de
Also note: If the interface declares the optional argument as well, then the result is a fatal error
in both 7.1.11 and 7.2.0RC6.
------------------------------------------------------------------------
[2017-11-29 17:02:56] christoph at burschka dot de
Description:
------------
In this inheritance chain, an interface defines a function without an argument, then an implementing
class adds an optional argument, and a subclass defines the function with the original signature
from the interface (no argument).
This works in PHP 7.1.11, but triggers E_ERROR in PHP 7.2.0RC6.
(Note: Without the interface, simply removing an optional argument in a subclass is E_WARNING on
both 7.1.11 and 7.2.0RC6.)
Test script:
---------------
interface A {
public function f();
}
class B implements A {
public function f(A $x = NULL) {}
}
class C extends B {
public function f() {}
}
Expected result:
----------------
Same behavior in PHP 7.2.0RC6 as PHP 7.1.11, or at worst a non-fatal warning/deprecation.
Actual result:
--------------
No warning in 7.1.11, E_ERROR in 7.2.0RC6.
------------------------------------------------------------------------
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