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Date: Wed, 16 Mar 2016 18:23:35 -0400
Message-ID: <CABDNdAHK297TFjsMPHCSQZPscKngrLexTjOLfxy0_Ks_cfgnyw@mail.gmail.com>
To: Andrey Andreev <narf@devilix.net>
Cc: Larry Garfield <larry@garfieldtech.com>, 
	"internals@lists.php.net" <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] [RFC Discussion] Typed Properties
From: pjsturgeon@gmail.com (Phil Sturgeon)

On Wed, Mar 16, 2016 at 6:17 PM, Andrey Andreev <narf@devilix.net> wrote:
> On Thu, Mar 17, 2016 at 12:00 AM, Larry Garfield <larry@garfieldtech.com>
> wrote:
>
>> On 3/16/16 2:30 PM, Andrey Andreev wrote:
>>
>>> Also, a LOT of code would end up with e.g. a default value of 0 for an
>>> integer property, still having to check if it was properly populated with a
>>> positive value - not much of an improvement over NULLs. Cheers, Andrey.
>>>
>>
>> That's fine.  Type checking doesn't say that a value is correct or
>> meaningful; it just enforces the shape of the data.
>>
>> Vis, type enforcement tells you that the property is an integer; it
>> doesn't tell you that the integer is within the range of legal values for
>> the temperature of a room.  It tells you that a property is a string; it
>> doesn't tell you that the string doesn't contain NSFW words.  Those are all
>> application-level concerns, not type-level concerns, no matter what we do
>> here.  (Just like they are for parameters and returns already.)
>>
>> IMO, int/string/float is only a big deal on properties if you're using
>> reflection for DB schema generation or similar, as it lets you remove an
>> annotation.  (That's a useful benefit, though.)  The bigger impact for me
>> is for class names, so I can enforce a given object type on a certain
>> property.  Knowing "at least it's not NULL" has a much larger benefit in
>> that case, as you avoid many "method called on non-object 100 execution
>> lines later than the actual bug, good luck finding it" errors. :-)
>
>
> Yet, your argument was about avoiding is_null() calls within application
> logic and you'd gain nothing if you end up having to write ! empty()
> instead. :)
> I'd rather have a NULL to tell me that I have nothing instead of a
> supposedly initialized but otherwise invalid value.
>
> Cheers,
> Andrey.

Not sure what you're saying there Andrey.

> That's fine.  Type checking doesn't say that a value is correct or meaningful; it just enforces the shape of the data.
> Larry

Solid points! Exactly that. A type relevant default of 0 is not
definitively invalid, it's up to application logic to work that out. 0
is totally valid as an integer.

I do quite like the idea of type relevant defaults being provided, so
0, [], "", etc, just like Go.

The only trouble I see there is: what sane default is given for
`public Foo $foo;`? Instantiate the class? Erf.