This is exactly why I asked you to provide a *complete* proposal.
Sent from my iPad
> On Aug 8, 2020, at 5:04 PM, fo...@univ-mlv.fr wrote:
>
>
>
>
> De: "Brian Goetz" <brian.go...@oracle.com>
> À: "Guy Steele" <guy.ste...@oracle.com>
> Cc: "Remi Forax" <fo...@univ-mlv.fr>, "amber-spec-experts"
> <amber-spec-experts@openjdk.java.net>, "John Rose" <john.r.r...@oracle.com>
> Envoyé: Vendredi 7 Août 2020 16:48:13
> Objet: Re: Nullable switch
>
> Okay, so it would seem that we need two keywords (or other syntax) for use in
> patterns; I will temporarily call them “anything-but-null” and
> “anything-including-null”.
>
> Not necessarily; the approach we've been driving towards has no (new)
> keywords, and no _explicit_ consideration of nullability. There's just type
> patterns, but their semantics take into account whether or not the type
> pattern "covers" the target type. This is subtle, I grant, and I can see
> where people would get confused, but it is far more compositional and less
> ad-hoc.
>
> Ignoring the epicyclical* distastefulness of the "any x" idea, I think the
> the syntax issues are a bit of a red herring -- the issue is structural.
> Under Remi's proposal, there is simply _no_ way to write a switch where any
> number of cases covers "anything including null", because the switch will
> throw before you get there:
>
> switch (x) {
> case String s:
> case Object o:
> }
>
> would throw on NPE (as switches do today) before any cases are considered,
> whether you say "var" or "any" or "Object."
>
> That is not true.
> You're right that the switch above will generate a NPE as the switches do
> today because under the rules i propose, there is no case that accept null.
>
> But if you add an any case (or a null case), then the switch will accept null,
> by example, the switch below accept null.
> switch (x) {
> case String s:
> case any o:
> }
>
> As Guy said, i'm proposing to have two different cases, one
> “anything-but-null” and one “anything-including-null” instead of relying on
> the non-local property of totality.
>
> You can re-read my email from the 6th of August for the rules allowing a
> switch to accept null and more examples.
>
> regards,
> Rémi
>
