Ecosystem

Code size reductions
Reduced heap overhead
Swift now sits below Foundation in the stack, so it can be used to create frameworks and drivers that word previously have required c.
New compiler diagnostics and guided errors
Improved code completion results and speed, especially for swiftUI
Improved indentation formatting
Improvements in debugging
Updated support for Ubuntu, added Centos and amazon. Official windows support coming soon.
- Swift AWS Lambda framework

Language and library

Multiple trailing-closures
Pass a key path to a function argument
@main Standarize a programs entry point
Reduced requirements to need self. in closures
Improved catch clause to have power of switch
Extended DSLs to support if let and switch
New Float16, half size float with smaller range
Apple Archive
Swift System, calls to system level apis
Improved OSLog
Swift Numerics, a math library
Swift ArgumentParser, a new package for parsing command line arguments
Swift StandardLKibraryPreview, a package for code that has been approved, but has not landed into a release yet
- Provides a simpler method for implementing proposed language changes