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Date: Sat, 1 May 2004 22:09:32 +0200
Reply-To: Marcus Boerger <helly@php.net>
Message-ID: <243202120.20040501220932@marcus-boerger.de>
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Subject: [RFC] Type hints
From: helly@php.net (Marcus Boerger)

Hello internals,

  while working with php 5 the last days i find it more and more
annoying that we allow NULL with type hints. From my perspective
allowing NULL with typehints would happen only very rare. So i
looked into the issue once again and prepared a patch.

  first i looked back the mails for this issue and found three
possible solutions:

1) (Zeev) allow NULL only when it is the first default argument.
Here the disadvantage is that you cannot have non default parameters
after one that allows NULL. Also this would introduce a BC break if
we'd go this way after 5.0 is out because it changes the standard
behavior.

2) (Andi) introduce 'not null' after php 5.0. This won't introduce
a BC break. But it would require two new keywords 'NOT' and 'NULL'.
The latter is not a problem because it is a define at the moment
and the patch (a) shows that it easy to change it into a keyword.
The problem is the new keyword 'not' which would introduce a BC
break for everyone using the word 'not' already.

3) (Myself) introduce 'or null'. Obviously this would introduce a
BC break when implemented after PHP 5.0 is out. The advantage is
that it only requires NULL as an additional keyword (see above)
and that it reflects the code it replaces. The replacement code
is to check whether the parameter is an instance of the typehint
"or" if specified check if it is null:

func(Classname or NULL $param) {}

replaces

func($param) {
  if ($param instanceof Classname or is_null($param)) {
     // ok
  } else {
    // error
  }
}

Having listed the three ideas i think we must address this issue
now and cannot delay it until after php 5.0 is out. Because of
2's additional keyword and 1's disadvantage i like 3 most. The
patch (b) implements it and adds a testfile.

Patch (c) also implements typehints for 'array' and 'class'.
Array checks the parameter for being an array and class checks
the parameter to be an instance of any class. These two we
agreed to do already and so i added an updated patch for it
which also includes the 'or null'.

(a) http://somabo.de/php/ext/ze2/ze2-null-patch-20040501.diff.txt
(b) http://somabo.de/php/ext/ze2/ze2-type-hints-null-20040501.diff.txt
(c) http://somabo.de/php/ext/ze2/ze2-type-hints-20040501.diff.txt

p.s.: As a sideeffect these patches speedup NULL handling.

Best regards,
 Marcus