Nestmates

[John Rose]

On Feb 17, 2016, at 12:15 PM, Peter Levart <peter.levart at gmail.com> wrote:
> 
> Suppose javac generates a random nest id for each nest (say 128 bit UUID). Two classes are nest-mates if they belong to the same module *and* share the same nest id.

There are two parts to this proposal:

1. New naming convention for nests, based on UUIDs.  This is a new concept in the JVM, and would require new infrastructure to manage (generate, transcode, verify, reflect, debug).  That means new bugs and new attack surfaces.  In the absence of a decisive benefit, it's better to reuse existing name spaces, and (in particular) the JVM's type name dictionary.

2. Unidirectional links.  The UUID, being a pure identity with no content, does not contain a list of its nestlings.  The nestlings point to the nest (via the UUID).  Any class can inject itself into a nest (in the same package) simply by mentioning the appropriate UUID.  Unidirectional linkage means that there is no way to enumerate a nest.  This complicates some optimizations (based on sealed types).  Security and seal-ability of nests is reduced to that of packages.  PRIVATE becomes just an alias for default-scope access control.

Sorry, but neither part of this is appealing to me, compared with the current proposal.

— John