> De: "Tagir Valeev" <amae...@gmail.com>
> À: "Brian Goetz" <brian.go...@oracle.com>
> Cc: "Remi Forax" <fo...@univ-mlv.fr>, "amber-spec-experts"
> <amber-spec-experts@openjdk.java.net>
> Envoyé: Dimanche 30 Août 2020 16:55:14
> Objet: Re: When several patterns are total ?
> Interesting!
> How about
> try {...}
> catch(Ex1 | Ex2 e) {
> switch (e) {
> case Ex1 -> ...
> case Ex2 -> ...
> }
> }
> ?
I also wonder if the precise exception trick should work:
try { ... }
catch(IllegalAccesException | NoSuchMethodException e) {
throw switch(e) {
case ReflectiveOperationException e -> e;
};
}
from the POV of the compiler, it's like throwing IllegalAccesException |
NoSuchMethodException and not ReflectiveOperationException.
so the code can be refactored to
try { ... }
catch(IllegalAccesException | NoSuchMethodException e) {
throw e;
}
> With best regards,
> Tagir Valeev.
Rémi
> вс, 30 авг. 2020 г., 21:38 Brian Goetz < [ mailto:brian.go...@oracle.com |
> brian.go...@oracle.com ] >:
>> ,
>>> i've hinted that there is an issue with intersection type and totality, but
>>> we
>> > did not follow up.
>> > Here is the issue
>> > var value = flag? "foo": 42;
>> > switch(value) {
>> > case String s -> ...
>> > case Integer i -> ...
>> > case Serializable s ->
>> > case Comparable<?> c ->
>> > }
>>> given that the type of value is an intersection type Serializable &
>> > Comparable<?> & ...
>>> the last two cases are total with respect to the type of value. which does
>>> not
>> > go well with the current semantics that can only have one total case.
>> Let’s separate the issues here. The type involved is an infinite type, which
>> I
>> think we can agree is a distraction. But lets assume the type of value were
>> Serializable&Comparable (S&C for short.)
>> Because S&C <: S, the `case S` in your example is already total, so the
>> `case C`
>> should be a dead case and yield a compilation error. According to the rule we
>> have, `case S` is total on any U <: S, so it is total on S&C, so the current
>> model covers this, and the `case C` is identified as dead by the compiler.
>> Which makes sense because there’s no value it can match.
>> I’m not seeing the problem?
