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To: Yasuo Ohgaki <yohgaki@ohgaki.net>,
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Date: Thu, 17 Sep 2015 01:14:05 +0200
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Subject: Re: [PHP-DEV] Make strict mode more strict?
From: francois@php.net (=?UTF-8?Q?Fran=c3=a7ois_Laupretre?=)

Hi Yasuo,

Le 17/09/2015 00:10, Yasuo Ohgaki a écrit :
> Hi all,
>
> Assigning different type to already initialized variable is a bug most
> likely. There may be cases that variable should have several types,
> e.g. return INT for success and FALSE for failure, but programmers can
> use different variable or return value directly or make BOOL/NULL
> exception.

While I don't like the idea of 'auto-typing' a variable (assign it an 
immutable type depending on the first assignment), the idea is quite 
similar to one I proposed when we were discussing scalar type hinting : 
the possibility to assign a type hint to every variable/property. In 
order to be really usable, it requires compound types but that's a 
detail because, anyway, we will need compound types.

The problem is that, AFAIK, it implies a mechanism to attach an optional 
type hint to a zval, and check it each time a value is assigned. While 
this would be extremely powerful and could dramatically change the way 
PHP types are considered and handled, this is a huge and complex work, 
especially in terms of performance. IMO, this may be an idea for 8.0, 
not before. Anyway, I may be wrong, if you see a simpler way to 
implement your concept, I'm interested.

Regards

François