[swift-evolution] [Proposal] Sealed classes by default

[Slava Pestov]

> On Aug 14, 2016, at 2:17 AM, John Holdsworth via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 2) Contrary to arguments about the likely performance benefits of de-virtualisation of method dispatch it is
> likely to make Swift programs launch more slowly due to the dynamic linker having to slide large numbers
> of function pointers for most method calls (itself an expensive operation) whether a call is even made.
> 

The proposal is independent of any specific implementation strategy or ABI. If vtable dispatch is faster across module boundaries than function calls, we can continue using vtable dispatch.

We need to have a separate discussion about the implementation of open, public and final classes for ABI and resilience reasons anyway.

Slava