TypeErasure-Macro

A Swift Macro, that creates a Type Erased Enum from a Protocol

---

Type Erasure Macro to attach to a protocol with the following functionality:

• creates Any<ProtocolName> enum with the given Types as cases for safely getting underlying type
• new enum conforms to the same protocols as the attached protocol
• adds all protocol members & functions to this Type-Erased Enum
• adds value member to get the value of the enum as Protocol-Type
• adds static from function to map from a conforming model to the Type Erased enum

Usage:

After importing this Package via SPM you can attach the @TypeErasure macro to any Protocol and pass conforming types into it as an array to create cases for each type.

Example:

@TypeErasure([ModelA, ModelB])
protocol Proto {
  var x: String { get set }
}

expands to the following Type-Erased Enum:

enum AnyProto {
  /// given Types conforming to Proto
  case modelA(ModelA)
  case modelB(ModelB)

  /// underlying value as protocol
  var value: any Proto {
    switch self {
    case .modelA(let val as any Proto),
         .modelB(let val as any Proto):
      return val
    }
  }
  
  /// all members of the protocol passed through
  var x: String {
    self.value.x
  }
}