On Wed, 2011-06-08 at 10:38 +0200, Hannes Magnusson wrote:

Which means that class callable { } function f(callable $c) { } f(new callable); will be allowed by the parser but have a "strange" result? (This isn't the case w/ array type hints as array is a parser token and can't be used as class name (from userland at least))

If this feature is accepted we should have a good behavior there. I'm not sure whether the right solution is to disallow naming classes "callable" (or "callback" or whatever the name will be in the end)

Funny thing: Google Codesearch gives me one application defining an class Callable. In that specific case the above thing would work: http://google.com/codesearch/p?hl=en#vA7-IQSCKhE/trunk/php/framework/project/App/util/Callable.php&q=lang:php%20%22class%20callable%22&sa=N&cd=9&ct=rc

Sidenote: Looking for "class callback" gives me more false positives, but also a few places where that classname is being used: http://google.com/codesearch/p?hl=en#lYWaFFstwm4/tests/cases/libs/model/models.php&q=lang:php%20%22class%20callback%22&sa=N&cd=11&ct=rc http://google.com/codesearch/p?hl=en#PbKZfG2CZcc/trunk/phpQuery/phpQuery/Callback.php&q=lang:php%20%22class%20callback%22&sa=N&cd=12&ct=rc&l=29 http://google.com/codesearch/p?hl=en#f6tUYQTbHns/trunk/framework/activerecord/lib/CallBack.php&q=lang:php%20%22class%20callback%22&sa=N&cd=21&ct=rc ...

Ok. I assume NULL as default value would be allowed, though. This would be consistent for the language and allow such things:

function foo(callback $cb = NULL) { if (!$cb) { $cb = function() { /* .. default implementation */ } .... }

Good point. While I'd see that as defect, independently from scalar and other type hints ;-)

That is fine.

Having the behavior cleared I wonder how useful it is in practical terms. A class type hint guarantees me I can do a specific call to methods defined in the class/interface. The proposed type hint tells me I can call it in some way. It won't ensure that the signature is compatible with what I expect.

function foo(callable $cb) { $cb(); } foo("strpos"); // This one in fact is illegal but won't be prevented

But maybe this doesn't matter as type hints purely serve documentation (as E_RECOVERABLE are useless unless we make them Exceptions ...) while even for documentation purpose more information is needed.

johannes