I would like to suggest a few ideas for GSoc 2021 for the Swift world, I hope that this is the right place to make this proposal.
Swift on Windows
Windows now uses a binary format (ECMA-based) to describe the shape of the OS APIs. This capability is now used to produce both Rust and C# APIs that give access to the entire set of Windows APIs.
There are already MIT-licensed C# and Rust implementations of this bridge, and could serve as a blueprint to do this. It would allow Swift to be a first class citizen in Windows.
This can be completed during the summer.
Swift on Android
While there is an effort to support Swift on Android, it would be great to create a binding generator that would surface the Android API to Swift developers. Xamarin's open sourced tools have enough support to turn arbitrary Android APIs into C# APIs, and could be used as a reference.
I do not believe that the summer would be enough to complete the work, but it could certainly make some progress in that direction.
The Tokamak folks have built a SwiftUI engine that runs on WebAssembly and to some extend on Linux. It would be great to fund this effort to get this SwiftUI-like platform to be both more complete, and more polished.
Very good fit for summer of code.
"Swift Tool" support
I would love to have a way of creating command line tools in Swift installed into the system, or for the user, similar to
npm install which can turn the project into a command line tool that is installed into the system. This would make it convenient to distribute Unix commands written in Swift.
This would extend SwiftPM, so I would envision:
$ swift install --global
Very good fit for a summer of code event.