Feedback and comments on ARM proposal

Tim Peierls tim at
Sat Mar 21 09:54:02 PDT 2009

On Sat, Mar 21, 2009 at 12:08 PM, Joshua Bloch <jjb at> wrote:

> What about the magic marker interface (if you'll pardon my wordplay)? This
> may be difficult to specify.

There are spec issues to resolve with the magic package approach, too: What
do you do if an interface type extends two or more interfaces from Probably not hard to find reasonable answers, but you could
say the same about the magic marker approach.

I think the hard question is how much extensibility to allow up front. Magic
Marker would make language libertarians happy, possibly at the risk of
increased abuse of ARM. Magic Package is the conservative response; it
focuses on the known problems, while preventing all but the very determined
from creating their own auto types (with bootclasspath trickery).

I suppose Magic Package doesn't rule out later on granting new magic powers
to types in, including, say, the magic marker power.


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