Pattern Matching for instanceof (Preview 2)
forax at univ-mlv.fr
forax at univ-mlv.fr
Fri Feb 28 11:50:29 UTC 2020
> De: "Gavin Bierman" <gavin.bierman at oracle.com>
> À: "Remi Forax" <forax at univ-mlv.fr>
> Cc: "jan lahoda" <jan.lahoda at oracle.com>, "amber-spec-experts"
> <amber-spec-experts at openjdk.java.net>
> Envoyé: Mardi 18 Février 2020 16:16:40
> Objet: Re: Pattern Matching for instanceof (Preview 2)
>> On 18 Feb 2020, at 15:04, [ mailto:forax at univ-mlv.fr | forax at univ-mlv.fr ]
>> Hi Gavin,
>> ----- Mail original -----
>>> De: "Gavin Bierman" < [ mailto:gavin.bierman at oracle.com |
>>> gavin.bierman at oracle.com ] >
>>> À: "Remi Forax" < [ mailto:forax at univ-mlv.fr | forax at univ-mlv.fr ] >
>>> Cc: "jan lahoda" < [ mailto:jan.lahoda at oracle.com | jan.lahoda at oracle.com ] >,
>>> "amber-spec-experts" < [ mailto:amber-spec-experts at openjdk.java.net |
>>> amber-spec-experts at openjdk.java.net ] >
>>> Envoyé: Mardi 18 Février 2020 15:32:12
>>> Objet: Re: Pattern Matching for instanceof (Preview 2)
>>> [Just circling back to this, as I added a note about the grammar to the JEP
>>>> On 6 Feb 2020, at 20:38, Remi Forax < [ mailto:forax at univ-mlv.fr |
>>>> forax at univ-mlv.fr ] > wrote:
>>>> [moved to amber-spec]
>>>> ----- Mail original -----
>>>>> De: "jan lahoda" < [ mailto:jan.lahoda at oracle.com | jan.lahoda at oracle.com ] >
>>>>> À: "amber-dev" < [ mailto:amber-dev at openjdk.java.net |
>>>>> amber-dev at openjdk.java.net ] >
>>>>> Envoyé: Jeudi 6 Février 2020 21:18:52
>>>>> Objet: Pattern Matching for instanceof (Preview 2)
>>>>> Thanks to Gavin, Brian and Alex, there is a new draft JEP for Pattern
>>>>> Matching for instanceof (Preview 2):
>>>>> [ https://bugs.openjdk.java.net/browse/JDK-8235186 |
>>>>> https://bugs.openjdk.java.net/browse/JDK-8235186 ]
>>>>> Any feedback on the JEP is more than welcome!
>>>> so the difference with the previous preview is that deconstruction is added.
>>> That is correct.
>>>> I see two questions:
>>>> - the grammar allows to mix var and non-var for a given reference type, i think
>>>> that should only permitted if the non var is a deconstruction itself ?
>>> I don’t know what you mean here. There are two patterns, a type test pattern and
>>> a deconstruction pattern. In v2 we propose to support deconstruction patterns
>>> over record types *only*. A deconstruction pattern looks like this: Point(var
>>> a, var b), i.e. all the components are either (recursively) deconstruction
>>> patterns, or `var` <identifier>, i.e. with no type needed. I added a note to
>>> the JEP page pointing out that this is a starting point, and eventually we will
>>> support other patterns in the argument position, specifically <type>
>>> <identifier>; hopefully in this release.
>> Currently we don't support mixing var and non var in lambda parameters.
>> So my question is: does this pattern Point(var x, int y) that mix a 'var' and an
>> explicit type allowed or not ?
> Aha. So, we’re not at that stage yet - this isn’t allowed by the spec as it
> stands. This - and many other issues - is why I’m starting small…
> Do you have a preference?
I don't think it's a matter of preference,
we want to support things like
Rectangle(var p1, Point(var x, var y))
For the type pattern Rectangle(...), there is a mix between var and non var, no ?
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