When several patterns are total ?

[Tagir Valeev]

Interesting!

How about

try {...}
catch(Ex1 | Ex2 e) {
  switch (e) {
    case Ex1 -> ...
    case Ex2 -> ...
  }
}

?

With best regards,
Tagir Valeev.

вс, 30 авг. 2020 г., 21:38 Brian Goetz <brian.goetz at 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?