__JSONDecoder made public

JSONDecoder.swift

import Foundation

extension JSONDecoder {
    struct _Options {
        let dateDecodingStrategy: DateDecodingStrategy
        let dataDecodingStrategy: DataDecodingStrategy
        let nonConformingFloatDecodingStrategy: NonConformingFloatDecodingStrategy
        let keyDecodingStrategy: KeyDecodingStrategy
        let userInfo: [CodingUserInfoKey : Any]
    }
}

private var _iso8601Formatter: ISO8601DateFormatter = {
    let formatter = ISO8601DateFormatter()
    formatter.formatOptions = .withInternetDateTime
    return formatter
}()

internal protocol _JSONStringDictionaryDecodableMarker {
    static var elementType: Decodable.Type { get }
}

extension DecodingError {
    /// Returns a `.typeMismatch` error describing the expected type.
    ///
    /// - parameter path: The path of `CodingKey`s taken to decode a value of this type.
    /// - parameter expectation: The type expected to be encountered.
    /// - parameter reality: The value that was encountered instead of the expected type.
    /// - returns: A `DecodingError` with the appropriate path and debug description.
    internal static func _typeMismatch(at path: [CodingKey], expectation: Any.Type, reality: Any) -> DecodingError {
        let description = "Expected to decode \(expectation) but found \(_typeDescription(of: reality)) instead."
        return .typeMismatch(expectation, Context(codingPath: path, debugDescription: description))
    }

    /// Returns a description of the type of `value` appropriate for an error message.
    ///
    /// - parameter value: The value whose type to describe.
    /// - returns: A string describing `value`.
    /// - precondition: `value` is one of the types below.
    private static func _typeDescription(of value: Any) -> String {
        if value is NSNull {
            return "a null value"
        } else if value is NSNumber /* FIXME: If swift-corelibs-foundation isn't updated to use NSNumber, this check will be necessary: || value is Int || value is Double */ {
            return "a number"
        } else if value is String {
            return "a string/data"
        } else if value is [Any] {
            return "an array"
        } else if value is [String : Any] {
            return "a dictionary"
        } else {
            return "\(type(of: value))"
        }
    }
}

extension JSONDecoder.KeyDecodingStrategy {
    fileprivate static func _convertFromSnakeCase(_ stringKey: String) -> String {
        guard !stringKey.isEmpty else { return stringKey }

        // Find the first non-underscore character
        guard let firstNonUnderscore = stringKey.firstIndex(where: { $0 != "_" }) else {
            // Reached the end without finding an _
            return stringKey
        }

        // Find the last non-underscore character
        var lastNonUnderscore = stringKey.index(before: stringKey.endIndex)
        while lastNonUnderscore > firstNonUnderscore && stringKey[lastNonUnderscore] == "_" {
            stringKey.formIndex(before: &lastNonUnderscore)
        }

        let keyRange = firstNonUnderscore...lastNonUnderscore
        let leadingUnderscoreRange = stringKey.startIndex..<firstNonUnderscore
        let trailingUnderscoreRange = stringKey.index(after: lastNonUnderscore)..<stringKey.endIndex

        let components = stringKey[keyRange].split(separator: "_")
        let joinedString : String
        if components.count == 1 {
            // No underscores in key, leave the word as is - maybe already camel cased
            joinedString = String(stringKey[keyRange])
        } else {
            joinedString = ([components[0].lowercased()] + components[1...].map { $0.capitalized }).joined()
        }

        // Do a cheap isEmpty check before creating and appending potentially empty strings
        let result : String
        if (leadingUnderscoreRange.isEmpty && trailingUnderscoreRange.isEmpty) {
            result = joinedString
        } else if (!leadingUnderscoreRange.isEmpty && !trailingUnderscoreRange.isEmpty) {
            // Both leading and trailing underscores
            result = String(stringKey[leadingUnderscoreRange]) + joinedString + String(stringKey[trailingUnderscoreRange])
        } else if (!leadingUnderscoreRange.isEmpty) {
            // Just leading
            result = String(stringKey[leadingUnderscoreRange]) + joinedString
        } else {
            // Just trailing
            result = joinedString + String(stringKey[trailingUnderscoreRange])
        }
        return result
    }
}

extension JSONEncoder.KeyEncodingStrategy {
    fileprivate static func _convertToSnakeCase(_ stringKey: String) -> String {
        guard !stringKey.isEmpty else { return stringKey }

        var words : [Range<String.Index>] = []
        // The general idea of this algorithm is to split words on transition from lower to upper case, then on transition of >1 upper case characters to lowercase
        //
        // myProperty -> my_property
        // myURLProperty -> my_url_property
        //
        // We assume, per Swift naming conventions, that the first character of the key is lowercase.
        var wordStart = stringKey.startIndex
        var searchRange = stringKey.index(after: wordStart)..<stringKey.endIndex

        // Find next uppercase character
        while let upperCaseRange = stringKey.rangeOfCharacter(from: CharacterSet.uppercaseLetters, options: [], range: searchRange) {
            let untilUpperCase = wordStart..<upperCaseRange.lowerBound
            words.append(untilUpperCase)

            // Find next lowercase character
            searchRange = upperCaseRange.lowerBound..<searchRange.upperBound
            guard let lowerCaseRange = stringKey.rangeOfCharacter(from: CharacterSet.lowercaseLetters, options: [], range: searchRange) else {
                // There are no more lower case letters. Just end here.
                wordStart = searchRange.lowerBound
                break
            }

            // Is the next lowercase letter more than 1 after the uppercase? If so, we encountered a group of uppercase letters that we should treat as its own word
            let nextCharacterAfterCapital = stringKey.index(after: upperCaseRange.lowerBound)
            if lowerCaseRange.lowerBound == nextCharacterAfterCapital {
                // The next character after capital is a lower case character and therefore not a word boundary.
                // Continue searching for the next upper case for the boundary.
                wordStart = upperCaseRange.lowerBound
            } else {
                // There was a range of >1 capital letters. Turn those into a word, stopping at the capital before the lower case character.
                let beforeLowerIndex = stringKey.index(before: lowerCaseRange.lowerBound)
                words.append(upperCaseRange.lowerBound..<beforeLowerIndex)

                // Next word starts at the capital before the lowercase we just found
                wordStart = beforeLowerIndex
            }
            searchRange = lowerCaseRange.upperBound..<searchRange.upperBound
        }
        words.append(wordStart..<searchRange.upperBound)
        let result = words.map({ (range) in
            return stringKey[range].lowercased()
        }).joined(separator: "_")
        return result
    }
}

class __JSONDecoder : Decoder {
    // MARK: Properties

    /// The decoder's storage.
    var storage: _JSONDecodingStorage

    /// Options set on the top-level decoder.
    let options: JSONDecoder._Options

    /// The path to the current point in encoding.
    fileprivate(set) public var codingPath: [CodingKey]

    /// Contextual user-provided information for use during encoding.
    public var userInfo: [CodingUserInfoKey : Any] {
        return self.options.userInfo
    }

    // MARK: - Initialization

    /// Initializes `self` with the given top-level container and options.
    init(referencing container: Any, at codingPath: [CodingKey] = [], options: JSONDecoder._Options) {
        self.storage = _JSONDecodingStorage()
        self.storage.push(container: container)
        self.codingPath = codingPath
        self.options = options
    }

    // MARK: - Decoder Methods

    public func container<Key>(keyedBy type: Key.Type) throws -> KeyedDecodingContainer<Key> {
        guard !(self.storage.topContainer is NSNull) else {
            throw DecodingError.valueNotFound(KeyedDecodingContainer<Key>.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get keyed decoding container -- found null value instead."))
        }

        guard let topContainer = self.storage.topContainer as? [String : Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [String : Any].self, reality: self.storage.topContainer)
        }

        let container = _JSONKeyedDecodingContainer<Key>(referencing: self, wrapping: topContainer)
        return KeyedDecodingContainer(container)
    }

    public func unkeyedContainer() throws -> UnkeyedDecodingContainer {
        guard !(self.storage.topContainer is NSNull) else {
            throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get unkeyed decoding container -- found null value instead."))
        }

        guard let topContainer = self.storage.topContainer as? [Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [Any].self, reality: self.storage.topContainer)
        }

        return _JSONUnkeyedDecodingContainer(referencing: self, wrapping: topContainer)
    }

    public func singleValueContainer() throws -> SingleValueDecodingContainer {
        return self
    }
}

// MARK: - Decoding Storage

struct _JSONDecodingStorage {
    // MARK: Properties

    /// The container stack.
    /// Elements may be any one of the JSON types (NSNull, NSNumber, String, Array, [String : Any]).
    private(set) var containers: [Any] = []

    // MARK: - Initialization

    /// Initializes `self` with no containers.
    init() {}

    // MARK: - Modifying the Stack

    var count: Int {
        return self.containers.count
    }

    var topContainer: Any {
        precondition(!self.containers.isEmpty, "Empty container stack.")
        return self.containers.last!
    }

    mutating func push(container: __owned Any) {
        self.containers.append(container)
    }

    mutating func popContainer() {
        precondition(!self.containers.isEmpty, "Empty container stack.")
        self.containers.removeLast()
    }
}

// MARK: Decoding Containers

private struct _JSONKeyedDecodingContainer<K : CodingKey> : KeyedDecodingContainerProtocol {
    typealias Key = K

    // MARK: Properties

    /// A reference to the decoder we're reading from.
    private let decoder: __JSONDecoder

    /// A reference to the container we're reading from.
    private let container: [String : Any]

    /// The path of coding keys taken to get to this point in decoding.
    private(set) public var codingPath: [CodingKey]

    // MARK: - Initialization

    /// Initializes `self` by referencing the given decoder and container.
    init(referencing decoder: __JSONDecoder, wrapping container: [String : Any]) {
        self.decoder = decoder
        switch decoder.options.keyDecodingStrategy {
        case .useDefaultKeys:
            self.container = container
        case .convertFromSnakeCase:
            // Convert the snake case keys in the container to camel case.
            // If we hit a duplicate key after conversion, then we'll use the first one we saw. Effectively an undefined behavior with JSON dictionaries.
            self.container = Dictionary(container.map {
                key, value in (JSONDecoder.KeyDecodingStrategy._convertFromSnakeCase(key), value)
            }, uniquingKeysWith: { (first, _) in first })
        case .custom(let converter):
            self.container = Dictionary(container.map {
                key, value in (converter(decoder.codingPath + [_JSONKey(stringValue: key, intValue: nil)]).stringValue, value)
            }, uniquingKeysWith: { (first, _) in first })
        }
        self.codingPath = decoder.codingPath
    }

    // MARK: - KeyedDecodingContainerProtocol Methods

    public var allKeys: [Key] {
        return self.container.keys.compactMap { Key(stringValue: $0) }
    }

    public func contains(_ key: Key) -> Bool {
        return self.container[key.stringValue] != nil
    }

    private func _errorDescription(of key: CodingKey) -> String {
        switch decoder.options.keyDecodingStrategy {
        case .convertFromSnakeCase:
            // In this case we can attempt to recover the original value by reversing the transform
            let original = key.stringValue
            let converted = JSONEncoder.KeyEncodingStrategy._convertToSnakeCase(original)
            let roundtrip = JSONDecoder.KeyDecodingStrategy._convertFromSnakeCase(converted)
            if converted == original {
                return "\(key) (\"\(original)\")"
            } else if roundtrip == original {
                return "\(key) (\"\(original)\"), converted to \(converted)"
            } else {
                return "\(key) (\"\(original)\"), with divergent representation \(roundtrip), converted to \(converted)"
            }
        default:
            // Otherwise, just report the converted string
            return "\(key) (\"\(key.stringValue)\")"
        }
    }

    public func decodeNil(forKey key: Key) throws -> Bool {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        return entry is NSNull
    }

    public func decode(_ type: Bool.Type, forKey key: Key) throws -> Bool {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Bool.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Int.Type, forKey key: Key) throws -> Int {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Int.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Int8.Type, forKey key: Key) throws -> Int8 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Int8.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Int16.Type, forKey key: Key) throws -> Int16 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Int16.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Int32.Type, forKey key: Key) throws -> Int32 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Int32.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Int64.Type, forKey key: Key) throws -> Int64 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Int64.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: UInt.Type, forKey key: Key) throws -> UInt {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: UInt.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: UInt8.Type, forKey key: Key) throws -> UInt8 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: UInt8.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: UInt16.Type, forKey key: Key) throws -> UInt16 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: UInt16.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: UInt32.Type, forKey key: Key) throws -> UInt32 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: UInt32.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: UInt64.Type, forKey key: Key) throws -> UInt64 {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: UInt64.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Float.Type, forKey key: Key) throws -> Float {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Float.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: Double.Type, forKey key: Key) throws -> Double {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: Double.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode(_ type: String.Type, forKey key: Key) throws -> String {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: String.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func decode<T : Decodable>(_ type: T.Type, forKey key: Key) throws -> T {
        guard let entry = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "No value associated with key \(_errorDescription(of: key))."))
        }

        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = try self.decoder.unbox(entry, as: type) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath, debugDescription: "Expected \(type) value but found null instead."))
        }

        return value
    }

    public func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type, forKey key: Key) throws -> KeyedDecodingContainer<NestedKey> {
        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key,
                                            DecodingError.Context(codingPath: self.codingPath,
                                                                  debugDescription: "Cannot get \(KeyedDecodingContainer<NestedKey>.self) -- no value found for key \(_errorDescription(of: key))"))
        }

        guard let dictionary = value as? [String : Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [String : Any].self, reality: value)
        }

        let container = _JSONKeyedDecodingContainer<NestedKey>(referencing: self.decoder, wrapping: dictionary)
        return KeyedDecodingContainer(container)
    }

    public func nestedUnkeyedContainer(forKey key: Key) throws -> UnkeyedDecodingContainer {
        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        guard let value = self.container[key.stringValue] else {
            throw DecodingError.keyNotFound(key,
                                            DecodingError.Context(codingPath: self.codingPath,
                                                                  debugDescription: "Cannot get UnkeyedDecodingContainer -- no value found for key \(_errorDescription(of: key))"))
        }

        guard let array = value as? [Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [Any].self, reality: value)
        }

        return _JSONUnkeyedDecodingContainer(referencing: self.decoder, wrapping: array)
    }

    private func _superDecoder(forKey key: __owned CodingKey) throws -> Decoder {
        self.decoder.codingPath.append(key)
        defer { self.decoder.codingPath.removeLast() }

        let value: Any = self.container[key.stringValue] ?? NSNull()
        return __JSONDecoder(referencing: value, at: self.decoder.codingPath, options: self.decoder.options)
    }

    public func superDecoder() throws -> Decoder {
        return try _superDecoder(forKey: _JSONKey.super)
    }

    public func superDecoder(forKey key: Key) throws -> Decoder {
        return try _superDecoder(forKey: key)
    }
}

private struct _JSONUnkeyedDecodingContainer : UnkeyedDecodingContainer {
    // MARK: Properties

    /// A reference to the decoder we're reading from.
    private let decoder: __JSONDecoder

    /// A reference to the container we're reading from.
    private let container: [Any]

    /// The path of coding keys taken to get to this point in decoding.
    private(set) public var codingPath: [CodingKey]

    /// The index of the element we're about to decode.
    private(set) public var currentIndex: Int

    // MARK: - Initialization

    /// Initializes `self` by referencing the given decoder and container.
    init(referencing decoder: __JSONDecoder, wrapping container: [Any]) {
        self.decoder = decoder
        self.container = container
        self.codingPath = decoder.codingPath
        self.currentIndex = 0
    }

    // MARK: - UnkeyedDecodingContainer Methods

    public var count: Int? {
        return self.container.count
    }

    public var isAtEnd: Bool {
        return self.currentIndex >= self.count!
    }

    public mutating func decodeNil() throws -> Bool {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(Any?.self, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        if self.container[self.currentIndex] is NSNull {
            self.currentIndex += 1
            return true
        } else {
            return false
        }
    }

    public mutating func decode(_ type: Bool.Type) throws -> Bool {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Bool.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Int.Type) throws -> Int {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Int8.Type) throws -> Int8 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int8.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Int16.Type) throws -> Int16 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int16.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Int32.Type) throws -> Int32 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int32.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Int64.Type) throws -> Int64 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Int64.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: UInt.Type) throws -> UInt {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: UInt8.Type) throws -> UInt8 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt8.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: UInt16.Type) throws -> UInt16 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt16.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: UInt32.Type) throws -> UInt32 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt32.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: UInt64.Type) throws -> UInt64 {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: UInt64.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Float.Type) throws -> Float {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Float.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: Double.Type) throws -> Double {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: Double.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode(_ type: String.Type) throws -> String {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: String.self) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func decode<T : Decodable>(_ type: T.Type) throws -> T {
        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Unkeyed container is at end."))
        }

        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard let decoded = try self.decoder.unbox(self.container[self.currentIndex], as: type) else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.decoder.codingPath + [_JSONKey(index: self.currentIndex)], debugDescription: "Expected \(type) but found null instead."))
        }

        self.currentIndex += 1
        return decoded
    }

    public mutating func nestedContainer<NestedKey>(keyedBy type: NestedKey.Type) throws -> KeyedDecodingContainer<NestedKey> {
        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(KeyedDecodingContainer<NestedKey>.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get nested keyed container -- unkeyed container is at end."))
        }

        let value = self.container[self.currentIndex]
        guard !(value is NSNull) else {
            throw DecodingError.valueNotFound(KeyedDecodingContainer<NestedKey>.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get keyed decoding container -- found null value instead."))
        }

        guard let dictionary = value as? [String : Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [String : Any].self, reality: value)
        }

        self.currentIndex += 1
        let container = _JSONKeyedDecodingContainer<NestedKey>(referencing: self.decoder, wrapping: dictionary)
        return KeyedDecodingContainer(container)
    }

    public mutating func nestedUnkeyedContainer() throws -> UnkeyedDecodingContainer {
        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get nested keyed container -- unkeyed container is at end."))
        }

        let value = self.container[self.currentIndex]
        guard !(value is NSNull) else {
            throw DecodingError.valueNotFound(UnkeyedDecodingContainer.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get keyed decoding container -- found null value instead."))
        }

        guard let array = value as? [Any] else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: [Any].self, reality: value)
        }

        self.currentIndex += 1
        return _JSONUnkeyedDecodingContainer(referencing: self.decoder, wrapping: array)
    }

    public mutating func superDecoder() throws -> Decoder {
        self.decoder.codingPath.append(_JSONKey(index: self.currentIndex))
        defer { self.decoder.codingPath.removeLast() }

        guard !self.isAtEnd else {
            throw DecodingError.valueNotFound(Decoder.self,
                                              DecodingError.Context(codingPath: self.codingPath,
                                                                    debugDescription: "Cannot get superDecoder() -- unkeyed container is at end."))
        }

        let value = self.container[self.currentIndex]
        self.currentIndex += 1
        return __JSONDecoder(referencing: value, at: self.decoder.codingPath, options: self.decoder.options)
    }
}

extension __JSONDecoder : SingleValueDecodingContainer {
    // MARK: SingleValueDecodingContainer Methods

    private func expectNonNull<T>(_ type: T.Type) throws {
        guard !self.decodeNil() else {
            throw DecodingError.valueNotFound(type, DecodingError.Context(codingPath: self.codingPath, debugDescription: "Expected \(type) but found null value instead."))
        }
    }

    public func decodeNil() -> Bool {
        return self.storage.topContainer is NSNull
    }

    public func decode(_ type: Bool.Type) throws -> Bool {
        try expectNonNull(Bool.self)
        return try self.unbox(self.storage.topContainer, as: Bool.self)!
    }

    public func decode(_ type: Int.Type) throws -> Int {
        try expectNonNull(Int.self)
        return try self.unbox(self.storage.topContainer, as: Int.self)!
    }

    public func decode(_ type: Int8.Type) throws -> Int8 {
        try expectNonNull(Int8.self)
        return try self.unbox(self.storage.topContainer, as: Int8.self)!
    }

    public func decode(_ type: Int16.Type) throws -> Int16 {
        try expectNonNull(Int16.self)
        return try self.unbox(self.storage.topContainer, as: Int16.self)!
    }

    public func decode(_ type: Int32.Type) throws -> Int32 {
        try expectNonNull(Int32.self)
        return try self.unbox(self.storage.topContainer, as: Int32.self)!
    }

    public func decode(_ type: Int64.Type) throws -> Int64 {
        try expectNonNull(Int64.self)
        return try self.unbox(self.storage.topContainer, as: Int64.self)!
    }

    public func decode(_ type: UInt.Type) throws -> UInt {
        try expectNonNull(UInt.self)
        return try self.unbox(self.storage.topContainer, as: UInt.self)!
    }

    public func decode(_ type: UInt8.Type) throws -> UInt8 {
        try expectNonNull(UInt8.self)
        return try self.unbox(self.storage.topContainer, as: UInt8.self)!
    }

    public func decode(_ type: UInt16.Type) throws -> UInt16 {
        try expectNonNull(UInt16.self)
        return try self.unbox(self.storage.topContainer, as: UInt16.self)!
    }

    public func decode(_ type: UInt32.Type) throws -> UInt32 {
        try expectNonNull(UInt32.self)
        return try self.unbox(self.storage.topContainer, as: UInt32.self)!
    }

    public func decode(_ type: UInt64.Type) throws -> UInt64 {
        try expectNonNull(UInt64.self)
        return try self.unbox(self.storage.topContainer, as: UInt64.self)!
    }

    public func decode(_ type: Float.Type) throws -> Float {
        try expectNonNull(Float.self)
        return try self.unbox(self.storage.topContainer, as: Float.self)!
    }

    public func decode(_ type: Double.Type) throws -> Double {
        try expectNonNull(Double.self)
        return try self.unbox(self.storage.topContainer, as: Double.self)!
    }

    public func decode(_ type: String.Type) throws -> String {
        try expectNonNull(String.self)
        return try self.unbox(self.storage.topContainer, as: String.self)!
    }

    public func decode<T : Decodable>(_ type: T.Type) throws -> T {
        try expectNonNull(type)
        return try self.unbox(self.storage.topContainer, as: type)!
    }
}

// MARK: - Concrete Value Representations

private extension __JSONDecoder {
    /// Returns the given value unboxed from a container.
    func unbox(_ value: Any, as type: Bool.Type) throws -> Bool? {
        guard !(value is NSNull) else { return nil }

        if let number = value as? NSNumber {
            // TODO: Add a flag to coerce non-boolean numbers into Bools?
            if number === kCFBooleanTrue as NSNumber {
                return true
            } else if number === kCFBooleanFalse as NSNumber {
                return false
            }

        /* FIXME: If swift-corelibs-foundation doesn't change to use NSNumber, this code path will need to be included and tested:
        } else if let bool = value as? Bool {
            return bool
        */

        }

        throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
    }

    func unbox(_ value: Any, as type: Int.Type) throws -> Int? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int = number.intValue
        guard NSNumber(value: int) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return int
    }

    func unbox(_ value: Any, as type: Int8.Type) throws -> Int8? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int8 = number.int8Value
        guard NSNumber(value: int8) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return int8
    }

    func unbox(_ value: Any, as type: Int16.Type) throws -> Int16? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int16 = number.int16Value
        guard NSNumber(value: int16) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return int16
    }

    func unbox(_ value: Any, as type: Int32.Type) throws -> Int32? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int32 = number.int32Value
        guard NSNumber(value: int32) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return int32
    }

    func unbox(_ value: Any, as type: Int64.Type) throws -> Int64? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let int64 = number.int64Value
        guard NSNumber(value: int64) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return int64
    }

    func unbox(_ value: Any, as type: UInt.Type) throws -> UInt? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint = number.uintValue
        guard NSNumber(value: uint) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return uint
    }

    func unbox(_ value: Any, as type: UInt8.Type) throws -> UInt8? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint8 = number.uint8Value
        guard NSNumber(value: uint8) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return uint8
    }

    func unbox(_ value: Any, as type: UInt16.Type) throws -> UInt16? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint16 = number.uint16Value
        guard NSNumber(value: uint16) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return uint16
    }

    func unbox(_ value: Any, as type: UInt32.Type) throws -> UInt32? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint32 = number.uint32Value
        guard NSNumber(value: uint32) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return uint32
    }

    func unbox(_ value: Any, as type: UInt64.Type) throws -> UInt64? {
        guard !(value is NSNull) else { return nil }

        guard let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        let uint64 = number.uint64Value
        guard NSNumber(value: uint64) == number else {
            throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number <\(number)> does not fit in \(type)."))
        }

        return uint64
    }

    func unbox(_ value: Any, as type: Float.Type) throws -> Float? {
        guard !(value is NSNull) else { return nil }

        if let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse {
            // We are willing to return a Float by losing precision:
            // * If the original value was integral,
            //   * and the integral value was > Float.greatestFiniteMagnitude, we will fail
            //   * and the integral value was <= Float.greatestFiniteMagnitude, we are willing to lose precision past 2^24
            // * If it was a Float, you will get back the precise value
            // * If it was a Double or Decimal, you will get back the nearest approximation if it will fit
            let double = number.doubleValue
            guard abs(double) <= Double(Float.greatestFiniteMagnitude) else {
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Parsed JSON number \(number) does not fit in \(type)."))
            }

            return Float(double)

        /* FIXME: If swift-corelibs-foundation doesn't change to use NSNumber, this code path will need to be included and tested:
        } else if let double = value as? Double {
            if abs(double) <= Double(Float.max) {
                return Float(double)
            }

            overflow = true
        } else if let int = value as? Int {
            if let float = Float(exactly: int) {
                return float
            }

            overflow = true
        */

        } else if let string = value as? String,
            case .convertFromString(let posInfString, let negInfString, let nanString) = self.options.nonConformingFloatDecodingStrategy {
            if string == posInfString {
                return Float.infinity
            } else if string == negInfString {
                return -Float.infinity
            } else if string == nanString {
                return Float.nan
            }
        }

        throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
    }

    func unbox(_ value: Any, as type: Double.Type) throws -> Double? {
        guard !(value is NSNull) else { return nil }

        if let number = value as? NSNumber, number !== kCFBooleanTrue, number !== kCFBooleanFalse {
            // We are always willing to return the number as a Double:
            // * If the original value was integral, it is guaranteed to fit in a Double; we are willing to lose precision past 2^53 if you encoded a UInt64 but requested a Double
            // * If it was a Float or Double, you will get back the precise value
            // * If it was Decimal, you will get back the nearest approximation
            return number.doubleValue

        /* FIXME: If swift-corelibs-foundation doesn't change to use NSNumber, this code path will need to be included and tested:
        } else if let double = value as? Double {
            return double
        } else if let int = value as? Int {
            if let double = Double(exactly: int) {
                return double
            }

            overflow = true
        */

        } else if let string = value as? String,
            case .convertFromString(let posInfString, let negInfString, let nanString) = self.options.nonConformingFloatDecodingStrategy {
            if string == posInfString {
                return Double.infinity
            } else if string == negInfString {
                return -Double.infinity
            } else if string == nanString {
                return Double.nan
            }
        }

        throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
    }

    func unbox(_ value: Any, as type: String.Type) throws -> String? {
        guard !(value is NSNull) else { return nil }

        guard let string = value as? String else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }

        return string
    }

    func unbox(_ value: Any, as type: Date.Type) throws -> Date? {
        guard !(value is NSNull) else { return nil }

        switch self.options.dateDecodingStrategy {
        case .deferredToDate:
            self.storage.push(container: value)
            defer { self.storage.popContainer() }
            return try Date(from: self)

        case .secondsSince1970:
            let double = try self.unbox(value, as: Double.self)!
            return Date(timeIntervalSince1970: double)

        case .millisecondsSince1970:
            let double = try self.unbox(value, as: Double.self)!
            return Date(timeIntervalSince1970: double / 1000.0)

        case .iso8601:
            if #available(macOS 10.12, iOS 10.0, watchOS 3.0, tvOS 10.0, *) {
                let string = try self.unbox(value, as: String.self)!
                guard let date = _iso8601Formatter.date(from: string) else {
                    throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Expected date string to be ISO8601-formatted."))
                }

                return date
            } else {
                fatalError("ISO8601DateFormatter is unavailable on this platform.")
            }

        case .formatted(let formatter):
            let string = try self.unbox(value, as: String.self)!
            guard let date = formatter.date(from: string) else {
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Date string does not match format expected by formatter."))
            }

            return date

        case .custom(let closure):
            self.storage.push(container: value)
            defer { self.storage.popContainer() }
            return try closure(self)
        }
    }

    func unbox(_ value: Any, as type: Data.Type) throws -> Data? {
        guard !(value is NSNull) else { return nil }

        switch self.options.dataDecodingStrategy {
        case .deferredToData:
            self.storage.push(container: value)
            defer { self.storage.popContainer() }
            return try Data(from: self)

        case .base64:
            guard let string = value as? String else {
                throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
            }

            guard let data = Data(base64Encoded: string) else {
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath, debugDescription: "Encountered Data is not valid Base64."))
            }

            return data

        case .custom(let closure):
            self.storage.push(container: value)
            defer { self.storage.popContainer() }
            return try closure(self)
        }
    }

    func unbox(_ value: Any, as type: Decimal.Type) throws -> Decimal? {
        guard !(value is NSNull) else { return nil }

        // Attempt to bridge from NSDecimalNumber.
        if let decimal = value as? Decimal {
            return decimal
        } else {
            let doubleValue = try self.unbox(value, as: Double.self)!
            return Decimal(doubleValue)
        }
    }

    func unbox<T>(_ value: Any, as type: _JSONStringDictionaryDecodableMarker.Type) throws -> T? {
        guard !(value is NSNull) else { return nil }

        var result = [String : Any]()
        guard let dict = value as? NSDictionary else {
            throw DecodingError._typeMismatch(at: self.codingPath, expectation: type, reality: value)
        }
        let elementType = type.elementType
        for (key, value) in dict {
            let key = key as! String
            self.codingPath.append(_JSONKey(stringValue: key, intValue: nil))
            defer { self.codingPath.removeLast() }

            result[key] = try unbox_(value, as: elementType)
        }

        return result as? T
    }

    func unbox<T : Decodable>(_ value: Any, as type: T.Type) throws -> T? {
        return try unbox_(value, as: type) as? T
    }

    func unbox_(_ value: Any, as type: Decodable.Type) throws -> Any? {
        if type == Date.self || type == NSDate.self {
            return try self.unbox(value, as: Date.self)
        } else if type == Data.self || type == NSData.self {
            return try self.unbox(value, as: Data.self)
        } else if type == URL.self || type == NSURL.self {
            guard let urlString = try self.unbox(value, as: String.self) else {
                return nil
            }

            guard let url = URL(string: urlString) else {
                throw DecodingError.dataCorrupted(DecodingError.Context(codingPath: self.codingPath,
                                                                        debugDescription: "Invalid URL string."))
            }
            return url
        } else if type == Decimal.self || type == NSDecimalNumber.self {
            return try self.unbox(value, as: Decimal.self)
        } else if let stringKeyedDictType = type as? _JSONStringDictionaryDecodableMarker.Type {
            return try self.unbox(value, as: stringKeyedDictType)
        } else {
            self.storage.push(container: value)
            defer { self.storage.popContainer() }
            return try type.init(from: self)
        }
    }
}

//===----------------------------------------------------------------------===//
// Shared Key Types
//===----------------------------------------------------------------------===//

private struct _JSONKey : CodingKey {
    public var stringValue: String
    public var intValue: Int?

    public init?(stringValue: String) {
        self.stringValue = stringValue
        self.intValue = nil
    }

    public init?(intValue: Int) {
        self.stringValue = "\(intValue)"
        self.intValue = intValue
    }

    public init(stringValue: String, intValue: Int?) {
        self.stringValue = stringValue
        self.intValue = intValue
    }

    init(index: Int) {
        self.stringValue = "Index \(index)"
        self.intValue = index
    }

    static let `super` = _JSONKey(stringValue: "super")!
}

struct Point: Codable {
    let x: Int
    let y: Int
}

let pointDictionary = [ "x": 0, "y": 1]

// Inital example was too easy so also we might have
struct Score: Codable {
    let points: Int
    let name: String
}

let scoreDictionary: [String: Any] = [
    "points": 10,
    "name": "iOSDevZone"
]

let options = JSONDecoder._Options(dateDecodingStrategy: .deferredToDate,
                                   dataDecodingStrategy: .base64,
                                   nonConformingFloatDecodingStrategy: .throw,
                                   keyDecodingStrategy: .useDefaultKeys,
                                   userInfo: [:])

guard let score = try __JSONDecoder(referencing: scoreDictionary, at: [], options: options)
    .unbox(scoreDictionary, as: Score.self) else {
    throw DecodingError.valueNotFound(Score.self, DecodingError.Context(codingPath: [], debugDescription: "The given data did not contain a top-level value."))
}


score.points