try value.encode(to: self)

return self.storage.popContainer()

struct Test<V: Encodable>: Encodable {
    var value: V
}

_ = try JSONEncoder().encode([Test(value: [Float.infinity])])

func box<T: Encodable>(_ value: T) throws -> Any {
    switch value {
    case is Date, is NSDate: return try self.box(value as! Date)
    default: return try self.box_(value)
    }
}

// in _JSONEncoder.box(Date):
case .deferred: return try self.box_(date)
case .closure(let c): return try self.box_(date, closure: c)

func box_<T: Encodable>(_ value: T, at codingPath: [CodingKey]) throws -> Any {
    return try self.box_(value, at: codingPath, closure: {try $0.encode(to: $1) })
}

func box_<T: Encodable>(_ value: T, closure: (T, Encoder)throws->Void) throws -> Any {
    let depth = self.storage.count

    func popIfEncoded() -> Any? {
        switch self.storage.count {
        case depth + 1: return self.storage.removeLast()
        case depth: return nil
        default:
            if self.storage.count > depth + 1 {
                fatalError()
            } else {
                fatalError("encoder lost values from storage while encoding")
            }
        }
    }

    do {
        try closure(value, self)
    } catch {
        _ = popIfEncoded()
        throw error
    }

    return popIfEncoded() ?? { ()->Any in fatalError("value did not encode a value") }()  
}