When working in teams we often find ourselves writing code that will ultimately be used by others. In an effort to reduce potential bugs we should strive to write code that's impossible to misuse. One of Swift's greatest assets is its compile-time safety which prevents entire classes of bugs, but only when APIs are designed to leverage it. This talk demonstrates how to design your APIs to be fundamentally safer, catching errors at compile time rather than in production. These techniques apply to any Swift code, from single types to full SDKs.

We'll transform URLSession's unsafe imperative patterns into a type-safe, declarative networking library where the compiler becomes your documentation, actively telling you what you must, can and cannot do. You'll see how to apply modern Swift features such as macros, typed throws for exhaustive error handling, actor isolation for thread safety and more to make your APIs misuse-resistant.