Nominal typing or structural typing?

[Paulo Levi]

I'm worried about lambdas effect on the generation of classfiles

First, that they aren't held in a separate class file, because that is one
of the reasons anonymous classes are frowned for more performance sensitive
areas.
Second, that they reuse definitions with the same number and type of
arguments - structural typing - i don't really just want to replace
anonymous class runtime explosion with the lambda equivalent, but have
something better.

No kind of specialist at all, and don't even know if it's possible in the
java type system.