MemberMacros.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

// MARK: - Case Detection

/// Add computed properties named `is<Case>` for each case element in the enum.
@attached(member, names: arbitrary)
public macro CaseDetection() = #externalMacro(module: "MacroExamplesImplementation", type: "CaseDetectionMacro")

// MARK: - Custom Codable

@attached(member, names: named(CodingKeys))
public macro CustomCodable() = #externalMacro(module: "MacroExamplesImplementation", type: "CustomCodable")

@attached(peer)
public macro CodableKey(name: String) = #externalMacro(module: "MacroExamplesImplementation", type: "CodableKey")

// MARK: - Meta Enum

@attached(member, names: named(Meta))
public macro MetaEnum() = #externalMacro(module: "MacroExamplesImplementation", type: "MetaEnumMacro")

// MARK: - New Type

@attached(member, names: named(RawValue), named(rawValue), named(init(_:)))
public macro NewType<T>(_: T.Type) = #externalMacro(module: "MacroExamplesImplementation", type: "NewTypeMacro")

public protocol NewTypeProtocol: RawRepresentable {
  init(_ rawValue: RawValue)
}

extension NewTypeProtocol {
  public init(rawValue: RawValue) { self.init(rawValue) }
}

// We can automate conformance of a `NewType` to an arbitrary protocol `P` by extending `NewTypeProtocol`. A small but common set of examples follow.

extension NewTypeProtocol where Self: Equatable, RawValue: Equatable {
  public static func == (lhs: Self, rhs: Self) -> Bool { lhs.rawValue == rhs.rawValue }
}

extension NewTypeProtocol where Self: Comparable, RawValue: Comparable {
  public static func < (lhs: Self, rhs: Self) -> Bool { lhs.rawValue < rhs.rawValue }
}

extension NewTypeProtocol where Self: Hashable, RawValue: Hashable {
  public func hash(into hasher: inout Hasher) { rawValue.hash(into: &hasher) }
}

extension NewTypeProtocol where Self: Encodable, RawValue: Encodable {
  public func encode(to encoder: Encoder) throws {
    var container = encoder.singleValueContainer()
    try container.encode(rawValue)
  }
}

extension NewTypeProtocol where Self: Decodable, RawValue: Decodable {
  public init(from decoder: Decoder) throws {
    let container = try decoder.singleValueContainer()
    self.init(try container.decode(RawValue.self))
  }
}

extension NewTypeProtocol where Self: CustomStringConvertible, RawValue: CustomStringConvertible {
  public var description: String { rawValue.description }
}