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Date: Thu, 14 Apr 2016 10:35:44 -0600
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To: Tom Worster <fsb@thefsb.org>
Cc: php-internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Nullable Return Type Declaration
From: levim@php.net (Levi Morrison)

On Thu, Apr 14, 2016 at 9:39 AM, Tom Worster <fsb@thefsb.org> wrote:
> I would like to introduce for discussion an RFC proposing and arguing for
> Nullable Return Type Declaration in 7.1 and deferring for now more general
> relaxations of 7.0 type as proposed in Levi's two RFCs.
>
>   https://wiki.php.net/rfc/nullable_returns
>
> If anyone would like to collaborate on the RFC, I have a repo you may fork:
> https://gist.github.com/tom--/e95a10fbe4d34f8a72c9 (although guthub's
> formatting isn't lovely). I'm looking for help with implementation.
>
> Tom
>
>
>

I can appreciate that you want only the restricted union with null.
However, I do not see the point of disallowing it for parameter types
while allowing it for return types:

    function setLeft(Node $n = null) {
        $this->left = $n;
        $this->updateHeight();
    }

Why disallow the explicit union with null here instead of the default
parameter which does not exactly capture the desired semantics?
Calling `$node->setLeft()` is just odd, almost as if it was a mistake.
I would much prefer `$node->setLeft(null)` here. Basically, if we have
a feature for return types that exactly matches the semantics that we
occasionally want for the parameter types why forbid it?

Additionally, on occasion I'll see functions like this:

    function foo(Bar $b = null, $not_optional_param);

Why not allow nullable types on parameters to avoid that wonkiness
caused by default values of null?

    function foo(Bar | Null $b, $not_optional_param);

This is much better.