The good and the bad static pattern ?

[Remi Forax]

> De: "Tagir Valeev" <amaembo at gmail.com>
> À: "Amber Expert Group Observers" <amber-spec-observers at openjdk.java.net>
> Cc: "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Envoyé: Lundi 18 Janvier 2021 09:17:30
> Objet: Re: The good and the bad static pattern ?

> I think it should be essential to be able to declare a pattern outside of the
> type it matches. We cannot declare all possible string patterns inside the
> java.lang.String. People would like to declare their own string patterns.
> With best regards,

We may still be able to access pattern outside the type it match without supporting it as a static pattern. 
I'm thinking about a way that make the type explicitly. 

Same example with a tentative syntax (there may be a better one) 
switch(o) { 
case String.matcher("(a*)(b*)", var matcher) -> ... 
case String text && Integer.parseInt(text, var value) -> ... 
} 

cheers, 

> Tagir Valeev

Rémi 

> On Mon, Jan 18, 2021 at 3:03 PM Remi Forax < [ mailto:forax at univ-mlv.fr |
> forax at univ-mlv.fr ] > wrote:

>> In the last document sent by Brian, there is a notion of static Pattern.

>> Here is an example of static patterns
>> switch(o) {
>> case String.matcher("(a*)(b*)", matcher -> ...
>> case Integer.parseInt(var value) -> ...
>> }

>> The first pattern, check if o is an instance of a String that match the regex
>> "(a)(b)" and provides the Matcher to retrieve the matching groups.
>> The second pattern, check if o is an instance of a String and can be parsed as
>> an integer and bind that integer to value.

>> The first pattern correspond to an instance method inside java.lang.String,
>> while the second pattern correspond to a static method inside
>> java.lang.Integer.

>> One problem is that while it's obvious that the first pattern starts by checking
>> if o is an instanceof String,
>> it's far less clear from a user POV that the second pattern does exactly the
>> same thing and does not check if o is an instance of Integer.

>> So should we support the form of the second pattern, a static Pattern linked to
>> a static method ?
>> Or should we restrict ourselves to static patterns that are expressed as
>> instance method ?

>> regards,
>> Rémi