[PHP-DEV] Enforcing final in traits

Re: [PHP-DEV] Enforcing final in traits

Nikita Popov — Sat, 05 May 2012 11:30:01 +0200

On Sat, May 5, 2012 at 1:38 AM, Stefan Marr wrote:
>
> On 04 May 2012, at 21:46, Hannes Magnusson wrote:
>
>> On Fri, May 4, 2012 at 8:30 PM, Scott MacVicar wrote:
>>> This caused a few bugs for us / confusion. The final keyword is accepted inside a trait but it the class also defines a method without the final keyword this takes precedence.
>
> The methods in the class always take precedency.
>
> However, the final keyword might just be something I overlooked.
> It sounds sensible that if the final is not explicitly removed during composition to treat it as what final was meant for and check it against the methods defined in the class body as well.
>
> Scott, could you elaborate a bit of the use case of final in a trait?

Here is an example:
http://stackoverflow.com/questions/7104957/building-a-singleton-trait-with-php-5-4

Not the best things to use traits for, but probably something people
*will* try to do.

Nikita

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Re: [PHP-DEV] Enforcing final in traits

Stefan Marr — Sat, 05 May 2012 01:40:01 +0200

On 04 May 2012, at 21:46, Hannes Magnusson wrote:

> On Fri, May 4, 2012 at 8:30 PM, Scott MacVicar wrote:
>> This caused a few bugs for us / confusion. The final keyword is accepted inside a trait but it the class also defines a method without the final keyword this takes precedence.

The methods in the class always take precedency.

However, the final keyword might just be something I overlooked.
It sounds sensible that if the final is not explicitly removed during composition to treat it as what final was meant for and check it against the methods defined in the class body as well.

Scott, could you elaborate a bit of the use case of final in a trait?

> it also ignores visibility abstract and static..

abstract is not ignored.
An abstract method in a trait expresses a requirement to the host class (using class).

In general, the ppp visibilities are seen as hints for the standard usage of a trait, but can be changed during composition.

Thanks
Stefan

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Stefan Marr
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Re: [PHP-DEV] Enforcing final in traits

Hannes Magnusson — Fri, 04 May 2012 21:50:02 +0200

On Fri, May 4, 2012 at 8:30 PM, Scott MacVicar wrote:
> This caused a few bugs for us / confusion. The final keyword is accepted inside a trait but it the class also defines a method without the final keyword this takes precedence.
>

it also ignores visibility abstract and static..

I thought this was intentional?

-Hannes

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[PHP-DEV] Enforcing final in traits

Scott MacVicar — Fri, 04 May 2012 20:40:02 +0200

This caused a few bugs for us / confusion. The final keyword is accepted inside a trait but it the class also defines a method without the final keyword this takes precedence.

Two solutions:
Enforce final when a trait defines - https://whisky.macvicar.net/patches/0001-If-a-trait-declares-a-method-as-final-enforce-that.patch

Prohibit final form being used in a trait - https://whisky.macvicar.net/patches/002-traits-Disable-use-of-final-keyword.patch

I'm for the first solution here

- S
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