Key-Value Encoding in Swift 4

KeyValueCoderTests.swift

import Foundation
import XCTest

class TestKeyValueEncoder : XCTestCase {
    
    func testEncodingTopLevelEmptyStruct() {
        let empty = EmptyStruct()
        _testRoundTrip(of: empty)
    }
    
    func testEncodingTopLevelEmptyClass() {
        let empty = EmptyClass()
        _testRoundTrip(of: empty)
    }
    
    func testEncodingTopLevelSingleValueEnum() {
        let s1 = Switch.off
        /*_testEncodeFailure*/_testRoundTrip(of: s1)
        _testRoundTrip(of: TopLevelWrapper(s1))
        
        let s2 = Switch.on
        /*_testEncodeFailure*/_testRoundTrip(of: s2)
        _testRoundTrip(of: TopLevelWrapper(s2))
    }
    
    func testEncodingTopLevelSingleValueStruct() {
        let t = Timestamp(3141592653)
        /*_testEncodeFailure*/_testRoundTrip(of: t)
        _testRoundTrip(of: TopLevelWrapper(t))
    }
    
    func testEncodingTopLevelSingleValueClass() {
        let c = Counter()
        /*_testEncodeFailure*/_testRoundTrip(of: c)
        _testRoundTrip(of: TopLevelWrapper(c))
    }
    
    func testEncodingTopLevelStructuredStruct() {
        // Address is a struct type with multiple fields.
        let address = Address.testValue
        _testRoundTrip(of: address)
    }
    
    func testEncodingTopLevelStructuredClass() {
        // Person is a class with multiple fields.
        let person = Person.testValue
        _testRoundTrip(of: person)
    }
    
    func testEncodingTopLevelStructuredSingleStruct() {
        // Numbers is a struct which encodes as an array through a single value container.
        let numbers = Numbers.testValue
        _testRoundTrip(of: numbers)
    }
    
    func testEncodingTopLevelStructuredSingleClass() {
        // Mapping is a class which encodes as a dictionary through a single value container.
        let mapping = Mapping.testValue
        _testRoundTrip(of: mapping)
    }
    
    func testEncodingTopLevelDeepStructuredType() {
        // Company is a type with fields which are Codable themselves.
        let company = Company.testValue
        _testRoundTrip(of: company)
    }
    
    func testEncodingClassWhichSharesEncoderWithSuper() {
        // Employee is a type which shares its encoder & decoder with its superclass, Person.
        //let employee = Employee.testValue
        //_testRoundTrip(of: employee)
    }
    
    func testEncodingTopLevelNullableType() {
        // EnhancedBool is a type which encodes either as a Bool or as nil.
        /*_testEncodeFailure*/_testRoundTrip(of: EnhancedBool.true)
        /*_testEncodeFailure*/_testRoundTrip(of: EnhancedBool.false)
        /*_testEncodeFailure*/_testRoundTrip(of: EnhancedBool.fileNotFound)
        
        _testRoundTrip(of: TopLevelWrapper(EnhancedBool.true))
        _testRoundTrip(of: TopLevelWrapper(EnhancedBool.false))
        _testRoundTrip(of: TopLevelWrapper(EnhancedBool.fileNotFound))
    }
    
    func testNestedContainerCodingPaths() {
        let encoder = KeyValueEncoder(options: [.primitiveRootValues, .multipleRootContainers, .overwriteDuplicates])
        do {
            let _ = try encoder.encode(NestedContainersTestType())
        } catch let error as NSError {
            XCTAssert(false, "Caught error during encoding nested container types: \(error)")
        }
    }
    
    func testSuperEncoderCodingPaths() {
        let encoder = KeyValueEncoder(options: [.primitiveRootValues, .multipleRootContainers, .overwriteDuplicates])
        do {
            let _ = try encoder.encode(NestedContainersTestType(testSuperEncoder: true))
        } catch let error as NSError {
            XCTAssert(false, "Caught error during encoding nested container types: \(error)")
        }
    }
    
    //
    //
    //
    
    // TODO: Check if this === actual value
    private func _testRoundTrip<T : Codable & Equatable>(of value: T) {
        do {
            let encoder = KeyValueEncoder(options: [.primitiveRootValues, .overwriteDuplicates])
            let intermediate = try encoder.encode(value) as Any
            let decoder = KeyValueDecoder(options: [.primitiveRootValues])
            let output: T = try decoder.decode(intermediate) as T
            
            XCTAssertEqual(value, output, "Encode <--> Decode pass expected identical results.")
        } catch(let error) {
            XCTAssert(false, "Encode of top-level \(T.self) was not expected to fail. \(error)")
        }
    }
    
    private func _testEncodeFailure<T : Encodable>(of value: T) {
        do {
            let encoder = KeyValueEncoder(options: [.primitiveRootValues, .multipleRootContainers, .overwriteDuplicates])
            let _ = try encoder.encode(value)
            XCTAssert(false, "Encode of top-level \(T.self) was expected to fail.")
        } catch {}
    }
}














// MARK: - Helper Global Functions
func expectEqualPaths(_ lhs: [CodingKey?], _ rhs: [CodingKey?], _ prefix: String) {
    if lhs.count != rhs.count {
        XCTAssert(false, "\(prefix) [CodingKey?].count mismatch: \(lhs.count) != \(rhs.count)")
        return
    }
    
    for (key1, key2) in zip(lhs, rhs) {
        switch (key1?.intValue, key2?.intValue) {
        case (.none, .none): break
        case (.some(let i1), .none):
            XCTAssert(false, "\(prefix) CodingKey.intValue mismatch: \(type(of: key1))(\(i1)) != nil")
            return
        case (.none, .some(let i2)):
            XCTAssert(false, "\(prefix) CodingKey.intValue mismatch: nil != \(type(of: key2))(\(i2))")
            return
        case (.some(let i1), .some(let i2)):
            guard i1 == i2 else {
                XCTAssert(false, "\(prefix) CodingKey.intValue mismatch: \(type(of: key1))(\(i1)) != \(type(of: key2))(\(i2))")
                return
            }
            
            break
        }
        
        XCTAssertEqual(key1?.stringValue, key2?.stringValue, "\(prefix) CodingKey.stringValue mismatch: \(type(of: key1))('\(String(describing: key1?.stringValue))') != \(type(of: key2))('\(String(describing: key2?.stringValue))')")
    }
}

// MARK: - Test Types
/* FIXME: Import from %S/Inputs/Coding/SharedTypes.swift somehow. */

// MARK: - Empty Types
fileprivate struct EmptyStruct : Codable, Equatable {
    static func ==(_ lhs: EmptyStruct, _ rhs: EmptyStruct) -> Bool {
        return true
    }
}

fileprivate class EmptyClass : Codable, Equatable {
    static func ==(_ lhs: EmptyClass, _ rhs: EmptyClass) -> Bool {
        return true
    }
}

// MARK: - Single-Value Types
/// A simple on-off switch type that encodes as a single Bool value.
fileprivate enum Switch : Codable {
    case off
    case on
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        switch try container.decode(Bool.self) {
        case false: self = .off
        case true:  self = .on
        }
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .off: try container.encode(false)
        case .on:  try container.encode(true)
        }
    }
}

/// A simple timestamp type that encodes as a single Double value.
fileprivate struct Timestamp : Codable, Equatable {
    let value: Double
    
    init(_ value: Double) {
        self.value = value
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        value = try container.decode(Double.self)
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(self.value)
    }
    
    static func ==(_ lhs: Timestamp, _ rhs: Timestamp) -> Bool {
        return lhs.value == rhs.value
    }
}

/// A simple referential counter type that encodes as a single Int value.
fileprivate final class Counter : Codable, Equatable {
    var count: Int = 0
    
    init() {}
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        count = try container.decode(Int.self)
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(self.count)
    }
    
    static func ==(_ lhs: Counter, _ rhs: Counter) -> Bool {
        return lhs === rhs || lhs.count == rhs.count
    }
}

// MARK: - Structured Types
/// A simple address type that encodes as a dictionary of values.
fileprivate struct Address : Codable, Equatable {
    let street: String
    let city: String
    let state: String
    let zipCode: Int
    let country: String
    
    init(street: String, city: String, state: String, zipCode: Int, country: String) {
        self.street = street
        self.city = city
        self.state = state
        self.zipCode = zipCode
        self.country = country
    }
    
    static func ==(_ lhs: Address, _ rhs: Address) -> Bool {
        return lhs.street == rhs.street &&
            lhs.city == rhs.city &&
            lhs.state == rhs.state &&
            lhs.zipCode == rhs.zipCode &&
            lhs.country == rhs.country
    }
    
    static var testValue: Address {
        return Address(street: "1 Infinite Loop",
                       city: "Cupertino",
                       state: "CA",
                       zipCode: 95014,
                       country: "United States")
    }
}

/// A simple person class that encodes as a dictionary of values.
fileprivate class Person : Codable, Equatable {
    let name: String
    let email: String
    let website: URL?
    
    init(name: String, email: String, website: URL? = nil) {
        self.name = name
        self.email = email
        self.website = website
    }
    
    private enum CodingKeys : String, CodingKey {
        case name
        case email
        case website
    }
    
    // FIXME: Remove when subclasses (Employee) are able to override synthesized conformance.
    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        name = try container.decode(String.self, forKey: .name)
        email = try container.decode(String.self, forKey: .email)
        website = try container.decodeIfPresent(URL.self, forKey: .website)
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(name, forKey: .name)
        try container.encode(email, forKey: .email)
        try container.encodeIfPresent(website, forKey: .website)
    }
    
    func isEqual(_ other: Person) -> Bool {
        return self.name == other.name &&
            self.email == other.email &&
            self.website == other.website
    }
    
    static func ==(_ lhs: Person, _ rhs: Person) -> Bool {
        return lhs.isEqual(rhs)
    }
    
    class var testValue: Person {
        return Person(name: "Johnny Appleseed", email: "[email protected]")
    }
}

/// A class which shares its encoder and decoder with its superclass.
fileprivate class Employee : Person {
    let id: Int
    
    init(name: String, email: String, website: URL? = nil, id: Int) {
        self.id = id
        super.init(name: name, email: email, website: website)
    }
    
    enum CodingKeys : String, CodingKey {
        case id
    }
    
    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        id = try container.decode(Int.self, forKey: .id)
        try super.init(from: decoder)
    }
    
    override func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(id, forKey: .id)
        try super.encode(to: encoder)
    }
    
    override func isEqual(_ other: Person) -> Bool {
        if let employee = other as? Employee {
            guard self.id == employee.id else { return false }
        }
        
        return super.isEqual(other)
    }
    
    override class var testValue: Employee {
        return Employee(name: "Johnny Appleseed", email: "[email protected]", id: 42)
    }
}

/// A simple company struct which encodes as a dictionary of nested values.
fileprivate struct Company : Codable, Equatable {
    let address: Address
    var employees: [Employee]
    
    init(address: Address, employees: [Employee]) {
        self.address = address
        self.employees = employees
    }
    
    static func ==(_ lhs: Company, _ rhs: Company) -> Bool {
        return lhs.address == rhs.address && lhs.employees == rhs.employees
    }
    
    static var testValue: Company {
        return Company(address: Address.testValue, employees: [Employee.testValue])
    }
}

/// An enum type which decodes from Bool?.
fileprivate enum EnhancedBool : Codable {
    case `true`
    case `false`
    case fileNotFound
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        if container.decodeNil() {
            self = .fileNotFound
        } else {
            let value = try container.decode(Bool.self)
            self = value ? .true : .false
        }
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        switch self {
        case .true: try container.encode(true)
        case .false: try container.encode(false)
        case .fileNotFound: try container.encodeNil()
        }
    }
}

/// A type which encodes as an array directly through a single value container.
struct Numbers : Codable, Equatable {
    let values = [4, 8, 15, 16, 23, 42]
    
    init() {}
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        let decodedValues = try container.decode([Int].self)
        guard decodedValues == values else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "The Numbers are wrong!"))
        }
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(values)
    }
    
    static func ==(_ lhs: Numbers, _ rhs: Numbers) -> Bool {
        return lhs.values == rhs.values
    }
    
    static var testValue: Numbers {
        return Numbers()
    }
}

/// A type which encodes as a dictionary directly through a single value container.
fileprivate final class Mapping : Codable, Equatable {
    let values: [String : URL]
    
    init(values: [String : URL]) {
        self.values = values
    }
    
    init(from decoder: Decoder) throws {
        let container = try decoder.singleValueContainer()
        values = try container.decode([String : URL].self)
    }
    
    func encode(to encoder: Encoder) throws {
        var container = encoder.singleValueContainer()
        try container.encode(values)
    }
    
    static func ==(_ lhs: Mapping, _ rhs: Mapping) -> Bool {
        return lhs === rhs || lhs.values == rhs.values
    }
    
    static var testValue: Mapping {
        return Mapping(values: ["Apple": URL(string: "http://apple.com")!,
                                "localhost": URL(string: "http://127.0.0.1")!])
    }
}

struct NestedContainersTestType : Encodable {
    let testSuperEncoder: Bool
    
    init(testSuperEncoder: Bool = false) {
        self.testSuperEncoder = testSuperEncoder
    }
    
    enum TopLevelCodingKeys : Int, CodingKey {
        case a
        case b
        case c
    }
    
    enum IntermediateCodingKeys : Int, CodingKey {
        case one
        case two
    }
    
    func encode(to encoder: Encoder) throws {
        if self.testSuperEncoder {
            var topLevelContainer = encoder.container(keyedBy: TopLevelCodingKeys.self)
            expectEqualPaths(encoder.codingPath, [], "Top-level Encoder's codingPath changed.")
            expectEqualPaths(topLevelContainer.codingPath, [], "New first-level keyed container has non-empty codingPath.")
            
            let superEncoder = topLevelContainer.superEncoder(forKey: .a)
            expectEqualPaths(encoder.codingPath, [], "Top-level Encoder's codingPath changed.")
            expectEqualPaths(topLevelContainer.codingPath, [], "First-level keyed container's codingPath changed.")
            expectEqualPaths(superEncoder.codingPath, [TopLevelCodingKeys.a], "New superEncoder had unexpected codingPath.")
            
            _testNestedContainers(in: superEncoder, baseCodingPath: [TopLevelCodingKeys.a])
        } else {
            _testNestedContainers(in: encoder, baseCodingPath: [])
        }
    }
    
    func _testNestedContainers(in encoder: Encoder, baseCodingPath: [CodingKey?]) {
        expectEqualPaths(encoder.codingPath, baseCodingPath, "New encoder has non-empty codingPath.")
        
        // codingPath should not change upon fetching a non-nested container.
        var firstLevelContainer = encoder.container(keyedBy: TopLevelCodingKeys.self)
        expectEqualPaths(encoder.codingPath, baseCodingPath, "Top-level Encoder's codingPath changed.")
        expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath, "New first-level keyed container has non-empty codingPath.")
        
        // Nested Keyed Container
        do {
            // Nested container for key should have a new key pushed on.
            var secondLevelContainer = firstLevelContainer.nestedContainer(keyedBy: IntermediateCodingKeys.self, forKey: .a)
            expectEqualPaths(encoder.codingPath, baseCodingPath, "Top-level Encoder's codingPath changed.")
            expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath, "First-level keyed container's codingPath changed.")
            expectEqualPaths(secondLevelContainer.codingPath, baseCodingPath + [TopLevelCodingKeys.a], "New second-level keyed container had unexpected codingPath.")
            
            // Inserting a keyed container should not change existing coding paths.
            let thirdLevelContainerKeyed = secondLevelContainer.nestedContainer(keyedBy: IntermediateCodingKeys.self, forKey: .one)
            expectEqualPaths(encoder.codingPath, baseCodingPath, "Top-level Encoder's codingPath changed.")
            expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath, "First-level keyed container's codingPath changed.")
            expectEqualPaths(secondLevelContainer.codingPath, baseCodingPath + [TopLevelCodingKeys.a], "Second-level keyed container's codingPath changed.")
            expectEqualPaths(thirdLevelContainerKeyed.codingPath, baseCodingPath + [TopLevelCodingKeys.a, IntermediateCodingKeys.one], "New third-level keyed container had unexpected codingPath.")
            
            // Inserting an unkeyed container should not change existing coding paths.
            let thirdLevelContainerUnkeyed = secondLevelContainer.nestedUnkeyedContainer(forKey: .two)
            expectEqualPaths(encoder.codingPath, baseCodingPath + [], "Top-level Encoder's codingPath changed.")
            expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath + [], "First-level keyed container's codingPath changed.")
            expectEqualPaths(secondLevelContainer.codingPath, baseCodingPath + [TopLevelCodingKeys.a], "Second-level keyed container's codingPath changed.")
            expectEqualPaths(thirdLevelContainerUnkeyed.codingPath, baseCodingPath + [TopLevelCodingKeys.a, IntermediateCodingKeys.two], "New third-level unkeyed container had unexpected codingPath.")
        }
        
        // Nested Unkeyed Container
        do {
            // Nested container for key should have a new key pushed on.
            var secondLevelContainer = firstLevelContainer.nestedUnkeyedContainer(forKey: .b)
            expectEqualPaths(encoder.codingPath, baseCodingPath, "Top-level Encoder's codingPath changed.")
            expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath, "First-level keyed container's codingPath changed.")
            expectEqualPaths(secondLevelContainer.codingPath, baseCodingPath + [TopLevelCodingKeys.b], "New second-level keyed container had unexpected codingPath.")
            
            // Appending a keyed container should not change existing coding paths.
            let thirdLevelContainerKeyed = secondLevelContainer.nestedContainer(keyedBy: IntermediateCodingKeys.self)
            expectEqualPaths(encoder.codingPath, baseCodingPath, "Top-level Encoder's codingPath changed.")
            expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath, "First-level keyed container's codingPath changed.")
            expectEqualPaths(secondLevelContainer.codingPath, baseCodingPath + [TopLevelCodingKeys.b], "Second-level unkeyed container's codingPath changed.")
            expectEqualPaths(thirdLevelContainerKeyed.codingPath, baseCodingPath + [TopLevelCodingKeys.b, nil], "New third-level keyed container had unexpected codingPath.")
            
            // Appending an unkeyed container should not change existing coding paths.
            let thirdLevelContainerUnkeyed = secondLevelContainer.nestedUnkeyedContainer()
            expectEqualPaths(encoder.codingPath, baseCodingPath, "Top-level Encoder's codingPath changed.")
            expectEqualPaths(firstLevelContainer.codingPath, baseCodingPath, "First-level keyed container's codingPath changed.")
            expectEqualPaths(secondLevelContainer.codingPath, baseCodingPath + [TopLevelCodingKeys.b], "Second-level unkeyed container's codingPath changed.")
            expectEqualPaths(thirdLevelContainerUnkeyed.codingPath, baseCodingPath + [TopLevelCodingKeys.b, nil], "New third-level unkeyed container had unexpected codingPath.")
        }
    }
}

// MARK: - Helper Types

/// Wraps a type T so that it can be encoded at the top level of a payload.
fileprivate struct TopLevelWrapper<T: Codable & Equatable>: Codable, Equatable {
    let value: T
    init(_ value: T) {
        self.value = value
    }
    static func ==(_ lhs: TopLevelWrapper<T>, _ rhs: TopLevelWrapper<T>) -> Bool {
        return lhs.value == rhs.value
    }
}

KeyValueDecoder.swift

/* TODO: Support sharing the Coder with super. */

//
// MARK: KeyValueDecoder
//

///
public class KeyValueDecoder {
    
    ///
    public struct Options: OptionSet {
        public typealias RawValue = Int
        public var rawValue: Int
        public init(rawValue: RawValue) {
            self.rawValue = rawValue
        }
        
        ///
        public static let multipleRootContainers = Options(rawValue: 1 << 0)
        
        ///
        public static let primitiveRootValues = Options(rawValue: 1 << 1)
    }
    
    public let options: Options
    public init(options: Options = []) {
        self.options = options
    }
    
    private var root: DecoderContainer? = nil
    public func decode<T: Decodable>(_ value: Any) throws -> T {
        self.root = DecoderContainer(owner: self, codingPath: [], content: value)
        return try T(from: self.root!)
    }
    
    //
    // MARK: KeyValueDecoder -> KeyedContainer
    //
    
    ///
    private class KeyedContainer<Key: CodingKey>: KeyedDecodingChildContainer {
        internal class Box {
            var content: [DecodingChildContainer] = []
        }
        
        var codingPath: [CodingKey?]
        var children = Box()
        private let content: [String: Any]
        
        let owner: KeyValueDecoder
        init(owner: KeyValueDecoder, codingPath: [CodingKey?], content: [String: Any]) {
            self.owner = owner
            self.codingPath = codingPath
            self.content = content
        }
        
        //
        // MARK: KeyValueDecoder -> KeyedContainer -> Decoding
        //
        
        func decodeValue<T: Decodable>(forKey key: Key) throws -> T? {
            guard let outerValue = self.content[key.value()] else {
                return nil
            }
            guard let value = outerValue as? T else {
                let desc = "Expected type \(T.self) but container stored value \(outerValue)."
                throw DecodingError.typeMismatch(T.self, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            return value
        }
        
        //
        // MARK: KeyValueDecoder -> KeyedContainer -> ChildContainer
        //
        
        func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type, forKey key: Key) throws -> KeyedDecodingContainer<NestedKey> {
            guard let outerValue = self.content[key.value()] else {
                let desc = "No element matching key \(key) in the container."
                throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            guard let inside = outerValue as? [String: Any] else {
                let desc = "Expected type \(Dictionary<String, Any>.self) but container stored value \(outerValue)."
                throw DecodingError.typeMismatch(Dictionary<String, Any>.self, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            let container = KeyedContainer<NestedKey>(owner: self.owner, codingPath: self.codingPath + [key], content: inside)
            self.children.content.append(container)
            return KeyedDecodingContainer(container)
        }
        
        func nestedUnkeyedContainer(forKey key: Key) throws -> UnkeyedDecodingContainer {
            guard let outerValue = self.content[key.value()] else {
                let desc = "No element matching key \(key) in the container."
                throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            guard let inside = outerValue as? [Any] else {
                let desc = "Expected type \(Array<Any>.self) but container stored value \(outerValue)."
                throw DecodingError.typeMismatch(Array<Any>.self, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            let container = UnkeyedContainer(owner: self.owner, codingPath: self.codingPath + [key], content: inside)
            self.children.content.append(container)
            return container
        }
        
        func superDecoder() throws -> Decoder {
            let key = Key(stringValue: "super")! // or Key(intValue: 0)
            return try self.superDecoder(forKey: key)
        }
        
        func superDecoder(forKey key: Key) throws -> Decoder {
            guard let inside = self.content[key.value()] else {
                let desc = "No superDecoder element found in the container."
                throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            let container = DecoderContainer(owner: self.owner, codingPath: self.codingPath + [key], content: inside)
            self.children.content.append(container)
            return container
        }
        
        //
        // MARK: KeyValueDecoder -> KeyedContainer -> Misc
        //
        
        var allKeys: [Key] {
            return Array(self.content.keys).flatMap { Key(stringValue: $0) }
        }
        
        func contains(_ key: Key) -> Bool {
            return self.content.keys.contains(key.value())
        }
    }
    
    //
    // MARK: KeyValueDecoder -> UnkeyedContainer
    //
    
    ///
    private class UnkeyedContainer: UnkeyedDecodingChildContainer {
        private let content: [Any]
        var codingPath: [CodingKey?]
        var count: Int? = nil
        var children: [DecodingChildContainer] = []
        
        let owner: KeyValueDecoder
        init(owner: KeyValueDecoder, codingPath: [CodingKey?], content: [Any]) {
            self.owner = owner
            self.codingPath = codingPath
            self.content = content
            self.count = content.count
        }
        
        //
        // MARK: KeyValueDecoder -> UnkeyedContainer -> Decoding
        //
        
        func decodeValue<T: Decodable>() throws -> T? {
            guard let count = self.count, count > 0 else {
                return nil
            }
            let outerValue = self.content[self.content.count - count]
            guard let value = outerValue as? T else {
                let desc = "Expected type \(T.self) but container stored value \(outerValue)."
                throw DecodingError.typeMismatch(T.self, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            self.count = count - 1 // decrement
            return value
        }
        
        //
        // MARK: KeyValueDecoder -> UnkeyedContainer -> ChildContainer
        //
        
        func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type) throws -> KeyedDecodingContainer<NestedKey> {
            guard let count = self.count, count > 0 else {
                let desc = "No more elements remaining in the container."
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            let outerValue = self.content[self.content.count - count]
            guard let inside = outerValue as? [String: Any] else {
                let desc = "Expected type \(Dictionary<String, Any>.self) but container stored value \(outerValue)."
                throw DecodingError.typeMismatch(Dictionary<String, Any>.self, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            
            let container = KeyedContainer<NestedKey>(owner: self.owner, codingPath: self.codingPath + [nil], content: inside)
            self.children.append(container)
            self.count = count - 1 // decrement
            return KeyedDecodingContainer(container)
        }
        
        func nestedUnkeyedContainer() throws -> UnkeyedDecodingContainer {
            guard let count = self.count, count > 0 else {
                let desc = "No more elements remaining in the container."
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            let outerValue = self.content[self.content.count - count]
            guard let inside = outerValue as? [Any] else {
                let desc = "Expected type \(Array<Any>.self) but container stored value \(outerValue)."
                throw DecodingError.typeMismatch(Array<Any>.self, DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            
            let container = UnkeyedContainer(owner: self.owner, codingPath: self.codingPath + [nil], content: inside)
            self.children.append(container)
            self.count = count - 1 // decrement
            return container
        }

        func superDecoder() throws -> Decoder {
            guard let count = self.count, count > 0 else {
                let desc = "No more elements remaining in the container."
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            let outerValue = self.content[self.content.count - count]
            let container = DecoderContainer(owner: self.owner, codingPath: self.codingPath + [nil], content: outerValue)
            self.children.append(container)
            self.count = count - 1 // decrement
            return container
        }
        
        //
        // MARK: KeyValueDecoder -> UnkeyedContainer -> Misc
        //
        
        var isAtEnd: Bool {
            return self.count == nil || self.count == 0
        }
    }
    
    //
    // MARK: KeyValueDecoder -> SingleValueContainer
    //
    
    ///
    private class SingleValueContainer: SingleValueDecodingChildContainer {
        
        private let content: Any
        fileprivate var children: [DecodingChildContainer] {
            get { return [] } set { }
        }
        
        let owner: KeyValueDecoder
        init(owner: KeyValueDecoder, content: Any) {
            self.owner = owner
            self.content = content
        }
        
        //
        // MARK: KeyValueDecoder -> SingleValueContainer -> Decoding
        //
        
        func decodeNil() -> Bool {
            if case Optional<Any>.none = self.content {
                return true
            } else if case Optional<Any>.some(_) = self.content {
                return false
            }
            return false // uh...?
        }
        
        func decodeValue<T: Decodable>() throws -> T {
            guard case Optional<Any>.some(_) = self.content else {
                let desc = "Expected type \(T.self) but container stored nil."
                throw DecodingError.valueNotFound(T.self, DecodingError.Context(codingPath: [], debugDescription: desc))
            }
            guard let value = self.content as? T else {
                let desc = "Expected type \(T.self) but container stored value \(self.content)."
                throw DecodingError.typeMismatch(T.self, DecodingError.Context(codingPath: [], debugDescription: desc))
            }
            return value
        }
    }
    
    //
    // MARK: KeyValueDecoder -> DecoderContainer
    //
    
    private class DecoderContainer: DecoderDecodingChildContainer {
        internal class Box {
            var content: [DecodingChildContainer] = []
        }
        
        public var codingPath: [CodingKey?]
        public var userInfo: [CodingUserInfoKey : Any] = [:]
        
        fileprivate let owner: KeyValueDecoder
        internal var children = Box()
        fileprivate var content: Any = Optional<Any>.none as Any
        
        fileprivate init(owner: KeyValueDecoder, codingPath: [CodingKey?], content: Any) {
            self.owner = owner
            self.codingPath = codingPath
            self.content = content
        }
        
        //
        // MARK: KeyValueDecoder -> DecoderContainer -> ChildContainer
        //
        
        public func container<Key>(keyedBy type: Key.Type) throws -> KeyedDecodingContainer<Key> {
            try! throwIfExists()
            guard let inside = self.content as? [String: Any] else {
                let desc = "This decoder's content could not support a keyed container."
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            
            let container = KeyedContainer<Key>(owner: self.owner, codingPath: self.codingPath, content: inside)
            self.children.content.append(container)
            return KeyedDecodingContainer(container)
        }
        
        public func unkeyedContainer() throws -> UnkeyedDecodingContainer {
            try! throwIfExists()
            guard let inside = self.content as? [Any] else {
                let desc = "This decoder's content could not support an unkeyed container."
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            
            let container = UnkeyedContainer(owner: self.owner, codingPath: self.codingPath, content: inside)
            self.children.content.append(container)
            return container
        }
        
        public func singleValueContainer() throws -> SingleValueDecodingContainer {
            try! throwIfExists()
            if !self.owner.options.contains(.primitiveRootValues) {
                fatalError("This decoder does not support primitive root values.")
            }
            
            let container = SingleValueContainer(owner: self.owner, content: self.content)
            self.children.content.append(container)
            return container
        }
        
        //
        // MARK: KeyValueDecoder -> DecoderContainer -> Misc
        //
        
        private func throwIfExists() throws {
            if self.children.content.count > 0 && !self.owner.options.contains(.multipleRootContainers) {
                let desc = "This decoder is not configured to support multiple root containers."
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
        }
    }
}

//
// MARK: Helpers
//

///
fileprivate extension CodingKey {
    func value() -> String {
        return self.stringValue
    }
    func value() -> Int {
        if let i = self.intValue { return i }
        fatalError("requires an integer coding key")
    }
}

///
fileprivate protocol DecodingChildContainer {}

fileprivate protocol DecoderDecodingChildContainer: Decoder, DecodingChildContainer {}
fileprivate protocol KeyedDecodingChildContainer: KeyedDecodingContainerProtocol, DecodingChildContainer {
    func decodeValue<T: Decodable>(forKey: Key) throws -> T?
}
fileprivate protocol UnkeyedDecodingChildContainer: UnkeyedDecodingContainer, DecodingChildContainer {
    mutating func decodeValue<T: Decodable>() throws -> T?
}
fileprivate protocol SingleValueDecodingChildContainer: SingleValueDecodingContainer, DecodingChildContainer {
    func decodeNil() -> Bool
    func decodeValue<T: Decodable>() throws -> T
}

fileprivate extension KeyedDecodingChildContainer {
    func decodeIfPresent(_ type: Bool.Type, forKey key: Key) throws -> Bool? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Int.Type, forKey key: Key) throws -> Int? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Int8.Type, forKey key: Key) throws -> Int8? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Int16.Type, forKey key: Key) throws -> Int16? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Int32.Type, forKey key: Key) throws -> Int32? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Int64.Type, forKey key: Key) throws -> Int64? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: UInt.Type, forKey key: Key) throws -> UInt? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: UInt8.Type, forKey key: Key) throws -> UInt8? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: UInt16.Type, forKey key: Key) throws -> UInt16? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: UInt32.Type, forKey key: Key) throws -> UInt32? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: UInt64.Type, forKey key: Key) throws -> UInt64? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Float.Type, forKey key: Key) throws -> Float? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: Double.Type, forKey key: Key) throws -> Double? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent(_ type: String.Type, forKey key: Key) throws -> String? {
        return try decodeValue(forKey: key)
    }
    
    func decodeIfPresent<T: Decodable>(_ type: T.Type, forKey key: Key) throws -> T? {
        return try decodeValue(forKey: key)
    }
}

fileprivate extension UnkeyedDecodingChildContainer {
    mutating func decodeIfPresent(_ type: Bool.Type) throws -> Bool? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Int.Type) throws -> Int? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Int8.Type) throws -> Int8? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Int16.Type) throws -> Int16? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Int32.Type) throws -> Int32? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Int64.Type) throws -> Int64? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: UInt.Type) throws -> UInt? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: UInt8.Type) throws -> UInt8? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: UInt16.Type) throws -> UInt16? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: UInt32.Type) throws -> UInt32? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: UInt64.Type) throws -> UInt64? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Float.Type) throws -> Float? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: Double.Type) throws -> Double? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent(_ type: String.Type) throws -> String? {
        return try decodeValue()
    }
    
    mutating func decodeIfPresent<T: Decodable>(_ type: T.Type) throws -> T?  {
        return try decodeValue()
    }
}

fileprivate extension SingleValueDecodingChildContainer {
    func decode(_ type: Bool.Type) throws -> Bool {
        return try decodeValue()
    }
    
    func decode(_ type: Int.Type) throws -> Int {
        return try decodeValue()
    }
    
    func decode(_ type: Int8.Type) throws -> Int8 {
        return try decodeValue()
    }
    
    func decode(_ type: Int16.Type) throws -> Int16 {
        return try decodeValue()
    }
    
    func decode(_ type: Int32.Type) throws -> Int32 {
        return try decodeValue()
    }
    
    func decode(_ type: Int64.Type) throws -> Int64 {
        return try decodeValue()
    }
    
    func decode(_ type: UInt.Type) throws -> UInt {
        return try decodeValue()
    }
    
    func decode(_ type: UInt8.Type) throws -> UInt8 {
        return try decodeValue()
    }
    
    func decode(_ type: UInt16.Type) throws -> UInt16 {
        return try decodeValue()
    }
    
    func decode(_ type: UInt32.Type) throws -> UInt32 {
        return try decodeValue()
    }
    
    func decode(_ type: UInt64.Type) throws -> UInt64 {
        return try decodeValue()
    }
    
    func decode(_ type: Float.Type) throws -> Float {
        return try decodeValue()
    }
    
    func decode(_ type: Double.Type) throws -> Double {
        return try decodeValue()
    }
    
    func decode(_ type: String.Type) throws -> String {
        return try decodeValue()
    }
    
    func decode<T: Decodable>(_ type: T.Type) throws -> T  {
        return try decodeValue()
    }
}

KeyValueEncoder.swift

/* TODO: Support sharing the Coder with super. */

//
// MARK: KeyValueEncoder
//

///
public class KeyValueEncoder {
    
    ///
    public struct Options: OptionSet {
        public typealias RawValue = Int
        public var rawValue: Int
        public init(rawValue: RawValue) {
            self.rawValue = rawValue
        }
        
        ///
        public static let multipleRootContainers = Options(rawValue: 1 << 0)
        
        ///
        public static let primitiveRootValues = Options(rawValue: 1 << 1)
        
        ///
        public static let overwriteDuplicates = Options(rawValue: 1 << 2)
    }
    
    public let options: Options
    public init(options: Options = []) {
        self.options = options
    }
    
    private var root: EncoderContainer? = nil
    public func encode<T: Encodable>(_ value: T) throws -> Any {
        self.root = EncoderContainer(owner: self, codingPath: [])
        try value.encode(to: self.root!)
        return self.root!.values()
    }
    
    //
    // MARK: KeyValueEncoder -> KeyedContainer
    //
    
    ///
    private class KeyedContainer<Key: CodingKey>: KeyedEncodingChildContainer {
        let owner: KeyValueEncoder
        var codingPath: [CodingKey?]
        var children: [String: EncodingChildContainer] = [:]
        var content: [String: Encodable] = [:]
        
        init(owner: KeyValueEncoder, codingPath: [CodingKey?]) {
            self.owner = owner
            self.codingPath = codingPath
        }
        
        //
        // MARK: KeyValueEncoder -> KeyedContainer -> Encoding
        //
        
        func encode<T: Encodable>(value: T, forKey key: Key) throws {
            if let _ = self.content.index(forKey: key.value()), !self.owner.options.contains(.overwriteDuplicates) {
                let desc = "Key \(key) already exists in the container."
                throw EncodingError.invalidValue(value, EncodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
            self.content[key.value()] = value
        }
        
        func values() -> Any {
            var values = self.content as [String: Any]
            let childValues = self.children.mapValues { $0.values() }
            childValues.forEach { values[$0.key] = $0.value }
            return values
        }
        
        //
        // MARK: KeyValueEncoder -> KeyedContainer -> ChildContainer
        //
        
        func nestedContainer<NestedKey>(keyedBy keyType: NestedKey.Type, forKey key: Key) -> KeyedEncodingContainer<NestedKey> {
            let container = KeyedContainer<NestedKey>(owner: self.owner, codingPath: self.codingPath + [key])
            self.children[key.value()] = container
            return KeyedEncodingContainer(container)
        }
        
        func nestedUnkeyedContainer(forKey key: Key) -> UnkeyedEncodingContainer {
            let container = UnkeyedContainer(owner: self.owner, codingPath: self.codingPath + [key])
            self.children[key.value()] = container
            return container
        }
        
        func superEncoder() -> Encoder {
            let key = Key(stringValue: "super")! // or Key(intValue: 0)
            return self.superEncoder(forKey: key)
        }
        
        func superEncoder(forKey key: Key) -> Encoder {
            let container = EncoderContainer(owner: self.owner, codingPath: self.codingPath + [key])
            self.children[key.value()] = container
            return container
        }
    }
    
    //
    // MARK: KeyValueEncoder -> UnkeyedContainer
    //
    
    ///
    private class UnkeyedContainer: UnkeyedEncodingChildContainer {
        let owner: KeyValueEncoder
        var codingPath: [CodingKey?]
        var children: [EncodingChildContainer] = []
        var content: [Encodable] = []
        
        init(owner: KeyValueEncoder, codingPath: [CodingKey?]) {
            self.owner = owner
            self.codingPath = codingPath
        }
        
        //
        // MARK: KeyValueEncoder -> UnkeyedContainer -> Encoding
        //
        
        func encode<T: Encodable>(value: T) throws {
            self.content.append(value)
        }
        
        func values() -> Any {
            return (self.content as [Any]) + self.children.map { $0.values() }
        }
        
        //
        // MARK: KeyValueEncoder -> UnkeyedContainer -> ChildContainer
        //
        
        func nestedContainer<NestedKey>(keyedBy keyType: NestedKey.Type) -> KeyedEncodingContainer<NestedKey> {
            let container = KeyedContainer<NestedKey>(owner: self.owner, codingPath: self.codingPath + [nil])
            self.children.append(container)
            return KeyedEncodingContainer(container)
        }
        
        func nestedUnkeyedContainer() -> UnkeyedEncodingContainer {
            let container = UnkeyedContainer(owner: self.owner, codingPath: self.codingPath + [nil])
            self.children.append(container)
            return container
        }
        
        func superEncoder() -> Encoder {
            let container = EncoderContainer(owner: self.owner, codingPath: self.codingPath + [nil])
            self.children.append(container)
            return container
        }
        
        //
        // MARK: KeyValueEncoder -> UnkeyedContainer -> Misc
        //
        
        /*
        func throwIfExists<T: Encodable>(_ value: T, forKey key: Key) throws {
            if let _ = self.content.index(forKey: key.value()) {
                let desc = "Key \(key) already exists in the container."
                throw EncodingError.invalidValue(value, EncodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
        }
        */
    }
    
    //
    // MARK: KeyValueEncoder -> SingleValueContainer
    //
    
    ///
    private class SingleValueContainer: SingleValueEncodingChildContainer {
        fileprivate var children: [EncodingChildContainer] {
            get { return [] } set { }
        }
        var content: [Encodable] = [] // strange way to not deal with Optional.
        
        let owner: KeyValueEncoder
        init(owner: KeyValueEncoder) {
            self.owner = owner
        }
        
        //
        // MARK: KeyValueEncoder -> SingleValueContainer -> Encoding
        //
        
        func encodeNil() throws {
            if self.content.count > 0 && !self.owner.options.contains(.overwriteDuplicates) {
                let desc = "Value already exists in the container."
                throw EncodingError.invalidValue(self.content[0] as Any, EncodingError.Context(codingPath: [], debugDescription: desc))
            }
            self.content = []
        }
        
        func encode<T: Encodable>(value: T) throws {
            if self.content.count > 0 && !self.owner.options.contains(.overwriteDuplicates) {
                let desc = "Value already exists in the container."
                throw EncodingError.invalidValue(value as Any, EncodingError.Context(codingPath: [], debugDescription: desc))
            }
            self.content = [value]
        }
        
        func values() -> Any {
            return self.content.first as Any
        }
    }
    
    //
    // MARK: KeyValueCoder -> EncoderContainer
    //
    
    private class EncoderContainer: EncoderEncodingChildContainer {
        internal class Box {
            var content: [EncodingChildContainer] = []
        }
        
        fileprivate let owner: KeyValueEncoder
        public var codingPath: [CodingKey?]
        public var userInfo: [CodingUserInfoKey : Any] = [:]
        internal var children = Box()
        
        init(owner: KeyValueEncoder, codingPath: [CodingKey?]) {
            self.owner = owner
            self.codingPath = codingPath
        }
        
        //
        // MARK: KeyValueCoder -> EncoderContainer -> Encoding
        //
        
        // message, dictionary
        func container<Key>(keyedBy type: Key.Type) -> KeyedEncodingContainer<Key> {
            try! throwIfExists()
            let container = KeyedContainer<Key>(owner: self.owner, codingPath: self.codingPath)
            self.children.content.append(container)
            return KeyedEncodingContainer(container)
        }
        
        // array, set
        func unkeyedContainer() -> UnkeyedEncodingContainer {
            try! throwIfExists()
            let container = UnkeyedContainer(owner: self.owner, codingPath: self.codingPath)
            self.children.content.append(container)
            return container
        }
        
        // values
        func singleValueContainer() -> SingleValueEncodingContainer {
            try! throwIfExists()
            if !self.owner.options.contains(.primitiveRootValues) {
                fatalError("This encoder does not support primitive root values.")
            }
            
            let container = SingleValueContainer(owner: self.owner)
            self.children.content.append(container)
            return container
        }
        
        //
        // MARK: KeyValueCoder -> EncoderContainer -> Misc
        //
        
        private func throwIfExists() throws {
            if self.children.content.count > 0 && !self.owner.options.contains(.multipleRootContainers) {
                let desc = "This encoder is not configured to support multiple root containers."
                throw EncodingError.invalidValue(self, EncodingError.Context(codingPath: self.codingPath, debugDescription: desc))
            }
        }
        
        func values() -> Any {
            if self.owner.options.contains(.multipleRootContainers) {
                return self.children.content.map { $0.values() }
            } else {
                return self.children.content[0].values()
            }
        }
    }
}

//
// MARK: Helpers
//

///
fileprivate extension CodingKey {
    func value() -> String {
        return self.stringValue
    }
    func value() -> Int {
        if let i = self.intValue { return i }
        fatalError("requires an integer coding key")
    }
}

///
fileprivate protocol EncodingChildContainer {
    
    ///
    func values() -> Any
}

fileprivate protocol EncoderEncodingChildContainer: Encoder, EncodingChildContainer {}
fileprivate protocol KeyedEncodingChildContainer: KeyedEncodingContainerProtocol, EncodingChildContainer {
    mutating func encode<T: Encodable>(value: T, forKey: Key) throws
}
fileprivate protocol UnkeyedEncodingChildContainer: UnkeyedEncodingContainer, EncodingChildContainer {
    mutating func encode<T: Encodable>(value: T) throws
}
fileprivate protocol SingleValueEncodingChildContainer: SingleValueEncodingContainer, EncodingChildContainer {
    mutating func encodeNil() throws
    mutating func encode<T: Encodable>(value: T) throws
}

fileprivate extension KeyedEncodingChildContainer {
    mutating func encode(_ value: Bool, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Int, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Int8, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Int16, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Int32, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Int64, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: UInt, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: UInt8, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: UInt16, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: UInt32, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: UInt64, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Float, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: Double, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode(_ value: String, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
    
    mutating func encode<T: Encodable>(_ value: T, forKey key: Key) throws {
        try encode(value: value, forKey: key)
    }
}

fileprivate extension UnkeyedEncodingChildContainer {
    mutating func encode(_ value: Bool) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int8) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int16) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int32) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int64) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt8) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt16) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt32) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt64) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Float) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Double) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: String) throws {
        try self.encode(value: value)
    }
    
    mutating func encode<T: Encodable>(_ value: T) throws {
        try self.encode(value: value)
    }
}

fileprivate extension SingleValueEncodingChildContainer {
    mutating func encode(_ value: Bool) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int8) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int16) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int32) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Int64) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt8) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt16) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt32) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: UInt64) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Float) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: Double) throws {
        try self.encode(value: value)
    }
    
    mutating func encode(_ value: String) throws {
        try self.encode(value: value)
    }
    
    mutating func encode<T: Encodable>(_ value: T) throws {
        try self.encode(value: value)
    }
}