How does/will Mojo handle final classes?

Unless a class is

final

final

, it usually has poor performance. However, Python classes are almost always extendable (

final

final

was only added in 3.8 and doesn't enable optimizations in Python, IIRC).

How will Mojo handle this, and how will Mojo

structs

structs

handle similar issues (and subtyping) in later versions?

How does/will Mojo handle final classes? - Modular