> On Apr 9, 2018, at 1:14 PM, Brian Goetz <brian.go...@oracle.com> wrote:
>
> A form of fallthrough that I think may be more common in expression switches
> is when something wants to fall _into_ the default:
>
> int x = switch (y) {
> case "Foo" -> 1;
> case "Bar" -> 2;
>
> case null:
> default:
> // handle exceptional case here
> }
>
> Because `default` is not a pattern, we can't say:
>
> case null, default:
>
> here. (Well, we could make it one.) Though we could carve out an exception
> for such "trivial" fallthrough.
As a matter of terminology, I think it would be helpful for us to not call this
fallthrough at all. It creates a lot of confusion when somebody is making an
assertion about fallthrough, and it's unclear whether this kind of thing is
being included or not.
JLS is a good guide: grammatically, the body of a switch statement is a
sequence of SwitchBlocks, each of which has a sequence of SwitchLabels followed
by some BlockStatements.
https://docs.oracle.com/javase/specs/jls/se10/html/jls-14.html#jls-14.11
<https://docs.oracle.com/javase/specs/jls/se10/html/jls-14.html#jls-14.11>
JLS doesn't formally define the concept of "fallthrough" but I suggest we use
it to describe the situation in which control flows from one SwitchBlock to
another.
What you've illustrated is instead a "switch case with multiple
labels"—something deserving scrutiny on its own, but really a different sort of
problem than fallthrough.
—Dan
