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Date: Wed, 4 Feb 2015 20:36:38 +0100
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Subject: AW: [PHP-DEV] Allow dropping typehints during inheritance
From: php@tutteli.ch ("Robert Stoll")


> -----Urspr=C3=BCngliche Nachricht-----
> Von: Robert Stoll [mailto:php@tutteli.ch]
> Gesendet: Mittwoch, 4. Februar 2015 20:24
> An: 'Nikita Popov'; 'PHP internals'
> Betreff: AW: [PHP-DEV] Allow dropping typehints during inheritance
>=20
>=20
> > -----Urspr=C3=BCngliche Nachricht-----
> > Von: Nikita Popov [mailto:nikita.ppv@gmail.com]
> > Gesendet: Mittwoch, 4. Februar 2015 19:50
> > An: PHP internals
> > Betreff: [PHP-DEV] Allow dropping typehints during inheritance
> >
> > Hi internals!
> >
> > Currently we do not allow [1] removing a typehint during =
inheritance. For example the following code is not valid:
> >
> >     interface A {
> >         public function method(Typehint $param);
> >     }
> >     class B implements A {
> >         public function method($param);
> >     }
> >     // Fatal error: Declaration of B::method() must be compatible =
with
> > A::method(Typehint $param)
> >
> > The above code does *not* constitute an LSP violation, because =
B::method() accepts more inputs than A::method().
> > However we still forbid it.
> >
> > This is an issue, because it makes it impossible to add typehints to
> > parameters at a later point in time. I've seen this issue come up =
both
> > in userland code, as well as in a recent DateTime change, see
> > =
https://github.com/php/php-src/commit/8e19705a93d785cd1ff8ba3a69699b00
> > 169fea47
> > .
> >
> > Instead of reverting the DateTime BC break, I'm wondering if it
> > wouldn't be better to fix the root cause by making the inheritance =
check less strict and allow removing typehints?
> >
> > Thanks,
> > Nikita
> >
> > [1] This is a fatal error when interfaces or abstract methods are =
involved, otherwise this is an E_STRICT error.
>=20
> I do not entirely agree here since what you are proposing is not to =
introduce contravariance for parameters (which I would
> support) but remove the check entirely.
> In this sense it is an LSP violation (you cannot substitute A with B =
and guarantee the correctness) and therefore should not
> be introduced into PHP.
>=20
> Cheers,
> Robert
>=20
>=20
> --
> PHP Internals - PHP Runtime Development Mailing List To unsubscribe, =
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I have to correct myself, without type hint is equal to say any type and =
in this sense it is contravariance, all good to go :)