Why some Swift types only appear when you import two modules

Types like Map, PhotosPicker, and WebView don't live in SwiftUI itself but in hidden cross-import overlay modules that only load when two frameworks are imported together (e.g. MapKit and SwiftUI). This explains why the compiler throws 'cannot find X in scope' rather than a missing-import error when only one of the two imports is present. The piece explains how Apple structures these overlays inside the SDK, why it avoids forcing unrelated dependencies on apps, lists the most common overlay pairs shipped in the iOS 26 SDK, and gives a practical heuristic: when an expected type is missing, add the second import that matches the two frameworks it touches.

Nguồn: https://sarunw.com/posts/swift-cross-import-overlay. 8 Sync News chỉ tóm tắt và dẫn link; bản quyền nội dung thuộc tác giả và nguồn gốc.