On Fri, 1 Oct 2021 11:09:20 GMT, Pavel Rappo <pra...@openjdk.org> wrote:
>> It's hard to know how to make it fail at compile time. There are
>> essentially 3 groups of trees ... inline tags (and other trees that use
>> `DCEndPosTree`), block tags (the big block of cases round about line 177),
>> and "other". We could arguably move block tags into the `default` case and
>> use a type test, which would improve the future-safety. We could arguably
>> catch missing cases at runtime with suitable use of `IllegalStateException`.
>>
>> As for tests, we *do* have tests for `ProvidesTree` and `UsesTree`, but the
>> new `RangeChecker` didn't catch the missing case labels because the basic
>> checks in `RangeChecker` were satisfied by the code in the default case in
>> the switch statement.
>
> I agree that it might prove hard, if at all possible. That said, we should
> investigate this later, not in this PR. One potential direction for
> investigation would be "switching on sealed interfaces". A class or an
> interface can be a part of multiple sealed-interface hierarchies:
>
>
> sealed interface Tag permits Block, Inline {}
> sealed interface Block extends Tag permits Block1, Bimodal {}
> non-sealed interface Block1 extends Block {}
> sealed interface Inline extends Tag permits Inline1, Bimodal {}
> non-sealed interface Inline1 extends Inline {}
> non-sealed interface Bimodal extends Block, Inline {}
>
>
> After pattern matching for `switch` (currently in preview via JEP 406) has
> been standardized, the exhaustiveness of a switch could help us catch bugs at
> compile time. Possibly.
Maybe.
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PR: https://git.openjdk.java.net/jdk/pull/5510
