[Just circling back to this, as I added a note about the grammar to the JEP page…]
> On 6 Feb 2020, at 20:38, Remi Forax <fo...@univ-mlv.fr> wrote: > > [moved to amber-spec] > > ----- Mail original ----- >> De: "jan lahoda" <jan.lah...@oracle.com> >> À: "amber-dev" <amber-...@openjdk.java.net> >> Envoyé: Jeudi 6 Février 2020 21:18:52 >> Objet: Pattern Matching for instanceof (Preview 2) > >> Hi, >> >> 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 >> >> Any feedback on the JEP is more than welcome! >> >> Thanks, >> Jan > > 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. > - must the identifier of a pattern argument be the same name as the > corresponding record component ? > To be coherent with the fact that constructors requires the same names. Absolutely not! Note this does mean that you can write confusing code: record Point(int x, int y) { } if (o instanceof Point(var y, var x)) { … // y refers to x component, y refers to x component } (I’ll get my coat…) Thanks, Gavin
