generates the following bytecode for baz:
So it's wrapping the call to bar() in an additional function, which ends up being () => bar().
It would be nice if it didn't do this - it's not a huge deal, but it would be useful for a few cases where you want to use a call by name argument in an inner loop and this lets you hoist the Function0 passed to it out. It also means slightly fewer class files generated. It probably doesn't really matter though, so I'll mark this as minor.
Note that it does do the right thing already if you pass a call by name argument to another call by name argument, so hopefully this is easy to do.