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Subject: Re: RFC: Generics
From: me@stephencoakley.com (Stephen Coakley)

On 09/24/2015 03:43 PM, Dominic Grostate wrote:
> Hi Ben & Internals,
>
> I spent most of today and yesterday just getting used to the parser
> language.
> I was able to implement the basic syntax on most of the constructs, just to
> get a partial proof of concept going.
>
> https://github.com/orolyn/php-src/commit/ee731240eab1e5986152cadaaca6d3e5b921ba7d
>
> The generic patterns aren't actually used, this simply "allows" them to be
> present.  Also I haven't yet cleaned up the memory leaks.
> The hitch I ran into however was function calls.
>
> add_to_collection<MyClass>($collection, $object); // Sorry for the rather
> pointless example.
>
> This potentially matches an expression, therefore yacc can't use it.
>
> Another (minor) but annoying issue is that nested generics need to be
> written like:
>
> A<T<V> > // Note the space before the last '>'
> Else it will match T_SL
>
> I don't know if either of these issues can be neatly corrected, ##parsers
> told me it was impossible without some
> major hackery, so this might warrant discussion on the tokens used to
> define generic delimitation.
>
> Anyway see parsable example below.
>
> Dominic
>
> <?php
>
> // T = placeholder for syntax texting
>
> interface Y {}
> interface Z extends Y<T> {}
>
> class K {}
>
> class A extends K<T> implements Y, Z<T<T> >
> {
>          public function add<T>(K<J> > $a): Y<T>
>          {
>          }
> }
>
> function sample<T>(A<T> $a) {
>          echo 'OK' . PHP_EOL;
> }
>
> sample(new A());
>

I know this is just some experimentation, but requiring a space in 
nested templates would be ugly, so we'd want to figure something out to 
get around that. C++ initially required a space as well and it confuses 
people still to this day.

Thanks for doing this work so far.

-- 
Stephen