----- Mail original ----- > De: "Brian Goetz" <brian.go...@oracle.com> > À: "Remi Forax" <fo...@univ-mlv.fr>, "Gavin Bierman" > <gavin.bier...@oracle.com> > Cc: "amber-spec-experts" <amber-spec-experts@openjdk.java.net>, "jan lahoda" > <jan.lah...@oracle.com> > Envoyé: Mardi 18 Février 2020 16:14:57 > Objet: Re: Pattern Matching for instanceof (Preview 2)
>>> 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 ? > > Unequivocal "yes". There is a universe of patterns. Some might be > disallowed in certain contexts (e.g., `instanceof var x` seems kind of > silly), but once we decide on the set of patterns allowable in which > contexts, any pattern can be nested inside a deconstruction pattern. > > The `var x` pattern can equally be thought of as inference for a total > type pattern, or an "any" pattern; they are semantically equivalent. > > If you're asking "but why can I not mix them in a lambda", the answer > is: because we don't support partial inference in lambdas at this time. > We could, and we might someday. (If you're suggesting that the > consistency between the two superficially-related forms is the most > important consideration here, I would disagree.) with a record, there is no real inference, but when you will have several deconstructors, we will need inference, right ? Rémi
