Semantics of an empty PermittedSubtypes attribute for the VM

Brian Goetz brian.goetz at
Fri Apr 3 13:39:35 UTC 2020

> You might think I’m arguing here for allowing S to be
> an empty set, and I might in similar cases, but there are two
> other reasons to outlaw the edge case, rather than ask
> the spec. to account for it (either by extending the general
> rule, or adding a special rule).  First, if C wants to permit
> exactly zero subclasses, there’s already a notation for that.

… unless C is an interface. 

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