give me a summary of what's new in xcode16

Xcode 16 introduces several exciting new features and improvements to enhance the app development process. Here are some of the highlights:

Code Completion: Xcode 16 features an innovative new engine for code completion, powered by a model specifically trained for Swift and Apple SDKs. This engine uses your project symbols to customize suggestions and runs locally on your Mac, ensuring privacy and fast results.
Swift 6: A new language mode in Swift 6 provides concurrency safety guarantees, turning data races into compile-time issues, which improves code correctness and safety.
Build Improvements: Xcode 16 supercharges builds with explicit modules, offering improved parallelism, better diagnostics, and faster debugging. For C and Objective-C, explicit modules are enabled by default, while for Swift, you need to opt-in.
Previews: Xcode Previews now use a new dynamic linking architecture, which avoids rebuilding your project when switching between previews and builds, making the workflow smoother. The introduction of a previewable macro allows for more dynamic properties in previews.
Swiftassist: A new tool called Swiftassist acts as a companion for coding tasks, providing assistance with coding questions and experimenting with new APIs.
Instruments and Profiling: Xcode 16 includes a flame graph for profiling data, offering deeper insights into app performance. This visual tool helps identify performance issues effectively.
Localization and Debugging: Enhancements to localization workflows and debugging tools are also part of Xcode 16, making it easier to bring apps to a global audience and improve app quality.

For more detailed information, you can check out the session What’s new in Xcode 16.