[PHP-DEV] Generics

Hi list !

As someone who wants generics in PHP, please make the generics opt-in 
(via INI setting or declare()) - PHP is slow enough as it stands now - 
and adding reified generics will just make it even slower.

I was very sad to see that the only feasable kind of generics (type 
erased) in PHP had its RFC declined.

By making the reified generics opt-in, extension authors may still 
implement type erased generics and thus avoid the performance penalty - 
altough as extension cannot change PHP parsing - their would rely on two 
small changes to PHP itself (please see below)

Imagine two ways forward (to type-erased generics):

1. By wrapping generic "expressions" in comments ie.: $x = new 
Collection/*<int>*/();
      all IDEs would have no problems with generics - The community 
might even make plugins for all popular IDEs that check such generic 
expression against the codebase from inside the IDE (the place where it 
actually matters) - I did one as an expieriment a while back for VSCode 
myself

2. We might of course also imagine the slighty more troublesome path 
forward:
     Two new tokens were added to PHP:

|< (interpreted as /*)
and
 >| (interpreted as */)

This option would of course need IDE plugins to be updated to understand 
the new syntax

Regardless of going with 1 or 2, at compile time, all PHP would have to 
do was to substitute generic function/method parameters (such as T, K or 
V) with mixed
ie (in a class Collection/*<T>*/ :
.
public function add(T $item) : T {

}

T would be replaced by mixed - PHP would have to have a known list of 
such generic type parameter names (T, K, V - but it might be 
configurable as an INI setting)

A declare() at the top of a file could hint the compiler if this file 
needs the replace / if it uses generics

This approach would then leave the actual checking of the validity of 
any generic expressions/code to an extension (written in C) for instance 
via a method such  as:

/* {{{ proto int myextension_check_generics(string $dir)
     Verify usage of generics in $dir recursively */
PHP_FUNCTION(myextension_check_generics)
{
....
      RETURN_TRUE
}

This extension function would basically do what Psalm etc. do today - 
just in C for much better performance

I am well aware that the internals list is set on reified generics, but 
I still think that that would be another wrong turn by PHP (just like 
the pipe operator and more)

I do agree that the wrapping |< and >| appears ugly but just wanted 
something that required as few changes as possible.

Just my 5 cents...


/Henrik



-- 



Med venlig hilsen

Henrik Skov
/HSK Consulting/
Blegdamsvej 128B, 4
DK-2100 Copenhagen O
Tel.: +45 27 62 83 01
Email: [email protected]