Feedback on Sealed Types

[Brian Goetz]

> It may solve the enclosing issue because the ';' syntactically separate A, B and C from the content of I which is declared after the ';', so A, B and C can be top-level.

Trying to make these top level has the same “how do I find the source file” problem that aux classes have.  

> I kind a like the intellectual separation between 
> - a sealed interface which represent a closed type and requires a permit clause and
> - an enum interface which represent a sum type which is sugar on top of sealed interface + records.

This does have a certain appeal, as each construct underscores what it is for.  On the other hand, the return-on-sugar for the second is just not that big (unlike with records or enums).  Basically, you get to drop the word “record” and “implements I” a bunch of times — not clear it carries its weight.