Swift makes classes final if possible

FindFinalClasses.swift

#!/usr/bin/env bash
<% for type in types.classes { -%>
  <%_ if type.attributes["final"] != nil || type.attributes["open"] != nil || types.based[type.name]?.isEmpty == false { continue } -%>
<%_ _%>git grep -lz 'class <%= type.name %>' | xargs -0 perl -i'' -pE "s/class <%= type.name %>(?=\s|:)/final class <%= type.name %>/g"
<% } %>

Instruction.md

1. Read about dynamic dispatch and performance https://developer.apple.com/swift/blog/?id=27, Whether this will make big difference for you depends on whether you have WMO enabled etc.
2. Configure Sourcery https://github.com/krzysztofzablocki/Sourcery
3. Copy above FindFinalClasses.swift to your templates folder with .swiftemplate extension
4. Run Sourcery
5. chmod +x YourOutputFolder/FindFinalClasses.generated.swift
6. Run the file as executable ./YourOutputFolder/FindFinalClasses.generated.swift

All top level classes (not supporting nested ones for now) that aren't open or final already will become final.