What should I do to migrate my Swift 5.9 project to Swift 6

To migrate your Swift 5.9 project to Swift 6, you should follow a structured process to ensure a smooth transition, especially focusing on data race safety and concurrency improvements introduced in Swift 6. Here's a step-by-step guide based on the WWDC session "Migrate your app to Swift 6":

1. Enable Complete Concurrency Checking: Start by enabling complete concurrency checking for each module in your project. This will keep your project in Swift 5 mode but will provide warnings for code that would fail under Swift 6's enforced data isolation.

2. Resolve Warnings: Go through the warnings provided by the compiler and resolve them. This step is crucial as it prepares your code for the stricter concurrency checks in Swift 6.

3. Enable Swift 6 Mode: Once all warnings are resolved for a module, enable Swift 6 mode for that module. This locks in your changes and ensures that future modifications do not regress to an unsafe state.

4. Repeat for Each Module: Repeat the above steps for each module in your project. This incremental approach allows you to manage the migration process more effectively.

5. Refactor if Necessary: After enabling Swift 6 mode across all modules, consider refactoring your code to remove any unsafe opt-outs and to take full advantage of Swift 6's features.

6. Utilize Compiler Diagnostics: Use the compiler diagnostics as a guide to identify and fix potential bugs in your code. This acts like a pair programmer, helping you ensure code safety.

7. Adopt New Features: Explore and adopt new Swift 6 features, such as improved concurrency and data race safety, to enhance your app's performance and reliability.

For more detailed guidance, you can refer to the session Migrate your app to Swift 6 (07:26) which provides a comprehensive strategy for migration. Additionally, the session What’s new in Swift (26:07) covers the new language mode and data-race safety features in Swift 6.