I have a proposal for a translation strategy:
Casts to inline classes from their reference projections will be frequent. Because the reference projection is sealed to permit only the value projection, a cast is morally equivalent to a null check. We want to preserve this performance model, because otherwise we're reinventing boxing.
Going through `ldc X.class / invokevirtual Class.cast` will surely be slow in the interpreter, but also risks being slow elsewhere (as do many of the other options.)
So let me add to your list: is it time for a `checknonnull` bytecode, which throws NPE if null, or some other more flexible checking bytecode? (Alternatively, if we're saving bytecodes: `invokevirtual Object.<nullcheck>`), where <nullcheck> is a fake method that always links to a no-op, but invokevirtual NPEs on a null receiver.)
