Features I would like to see from Swift and its core ecosystem

Swift Wish List.md

Swift Wish List

Features I would like to see from Swift and its core ecosystem, to make it a robust and ergonomic language for all use cases.

• ❌ = Unimplemented / Pitch Status
• ⛔️ = Partially Implemented / Awaiting Implementation
• ⚠️ = In Active Review
• ✅ = Accepted / Implemented
• ☑️ = Available in Latest Version (5.4)

Language Features

• ❌ Memory ownership system
• ❌ Variadic generics
• ❌ Flexible memberwise initialization (rationale for initial rejection)

Concurrency

• ✅ async/await
• ⚠️ async let structured concurrency bindings
• ✅ Actors
• ❌ Global actors
• ✅ async program entry points
• ✅ AsyncSequence
  • ⚠️ AsyncStream
• ✅ Effectful properties (async and throws)

Protocols & Existentials

• ❌ Generic protocol type constraints directly on arguments and returns
  • ✅ Existentials for protocols with associatedtype constraints as new type definitions
• ☑️ Opaque result types (some)
• ❌ Existential result types (any)
• ❌ Metatype extensions
• ❌ Protocol self-conformance

Strings

• ❌ Regular expression literals
• ❌ More ergonomic indexing and slicing

Optionals

• ❌ Optional chaining operator (?) in orthogonal positions
• ❌ if let with any pattern match, not just optional unwraps
• ❌ Concise syntax for duplicate identifiers in if let bindings

Domain Specific Languages

• ☑️ Result builders
• ☑️ Implicit memberwise initializer
• ❌ Result builder protocol
• ☑️ Result builder let declarations
• ❌ Stateful result builders
• ❌ Virtualized ASTs (to convert native for-in loops to specialized types, like SwiftUI.ForEach)

Metaprogramming & Reflection

• ☑️ Property wrappers
• ❌ More ergonomic Codable customization
• ❌ First-class macro system
  • ❌ Pattern-matching macros, based on the aforementioned regular expression literals
  • ❌ Procedural macros
    • Based on SwiftSyntax and Mirror
    • Including its own result builder DSL
    • Definable @Attributes, so the macro can be applied to various definitions
  • ❌ A way to define default protocol implementations as a macro (with the ability to define helper @Attributes)
• ❌ Dynamic property iteration using key paths
• ❌ Tuple and Enum key paths
• ❌ Dependent types
• ❌ Ability to assert that all properties on a type conforming to a protocol must also conform to that protocol (as Codable does)

Modules

• ❌ Namespaces
• ❌ Fully qualified name syntax
• ❌ Formalized @exported attribute

Interoperability & Platform Support

• ❌ C++ interoperability
• ❌ Rust interoperability
• ❌ COM and WinRT interoperability
• ❌ Formalized generic external declarations (e.g. @decl)
• ❌ Upstream WebAssembly support

Ecosystem Features

• ❌ Official Swift-only testing library
• ❌ Formatted command line test output
• ❌ Toolchain manager
• ❌ Official HTML documentation generation tool

Standard Library & Foundation

• ⛔️ Open source Foundation implementation
• ❌ Replace Foundation with modern APIs, split into individually importable submodules

Swift Package Manager

• ⛔️ Support for scripting (awaiting implementation as part of Google SoC)
• ❌ Dynamic loading API
• ✅ Package editor commands
• ❌ Official package index
• ❌ Type-safe access to individual resource files
• ❌ Package features
• ✅ Extensible build tools
• ❌ Ad-hoc CLI actions
• ❌ Extensible Product types
• ❌ Package @Attributes

SwiftNIO

• ⛔️ async/await support
• ❌ QUIC and HTTP/3 support (see: Feature Use)