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Message-ID: <5751B50F.2090003@garfieldtech.com>
Date: Fri, 3 Jun 2016 11:49:19 -0500
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Subject: Re: [PHP-DEV] [RFC] [PRE-VOTE] Union types
From: larry@garfieldtech.com (Larry Garfield)

On 06/03/2016 10:16 AM, Jordi Boggiano wrote:
> On 03/06/2016 15:58, Thomas Bley wrote:
>> To me type declarations help to make my code easier and more consistent.
>> Having multiple scalar types for a single function parameter is 
>> against this goal since I need extra logic to handle this.
>>
>> e.g. function foo(string | int | bool $bar) {} makes no sense in weak 
>> mode since string can already handle int, bool, float, etc.
>>
>> having different behavior between
>> foo("42"); function foo(string $b) {echo gettype($b);} // string
>> and
>> foo("42"); function foo(string | int $b) {echo gettype($b);} // integer
>> also makes no sense to me.
>>
>> Things like string|array are useful (e.g. str_replace) since we can 
>> cast the string easily to array and calling a string parameter with 
>> an array would give a fatal error.
>
> That is a useful case, and don't forget also return values, e.g. all 
> the XX|false-kind of return types it's also nice to have.
>
> I don't think for function arguments it's massively useful and I doubt 
> it'll get put everywhere, but it's nice to be able to express this 
> when you have to.
>
> Cheers

For parameters, I really don't think | is going to be the common use 
case.  (It should still be rational, but I don't expect to see it day to 
day.)  InterfaceA & InterfaceB Is the more useful use case for 
parameters.  | is, as noted, likely more useful on returns. (even though 
I would discourage their use in most cases for reasons I won't go into 
here).

--Larry Garfield