On 8/18/2019 12:25 PM, Brian Goetz wrote:
So, given all this, we should focus all our ceremony-reduction on the
case of co-declared sum types. Which is mostly what I think I was
suggesting:
- Infer the permits clause when all the subtypes are co-declared;
- Infer “final” for leaf classes in a sum type;
- Require explicitness in both sealed/non-sealed, and permits clause,
in other cases.
How do you know from `sealed class X {}` and the rest of its compilation
unit that all X's subtypes are co-declared? Maybe there's another class
which extends X that someone forgot to pass to javac. Do you really mean
to determine which subfeature is in use (and hence whether ceremony
reduction is needed) based on what the host system can observe? I
wondered if your intention is for a top-level sealed RECORD class to
indicate sum-types code and a top-level sealed ABSTRACT class to
indicate restricted-hierarchy code, but you downplayed
abstract-superclass for restricted hierarchies earlier.
Alex
