title: Type of expression is ambiguous without more context swift 4.0
body: <p>i am implementing <strong>pod 'Socket.IO-Client-Swift</strong>'   </p>
  
  <p>but in <strong>SocketEngine.swift</strong> file i'm getting this error.</p>
  
  <pre><code> private func handleBase64(message: String) {
              // binary in base64 string
              let noPrefix = message[message.index(message.startIndex, offsetBy: 2)..&lt;message.endIndex]
  
              if let data = Data(base64Encoded: noPrefix, options: .ignoreUnknownCharacters) {
                  client?.parseEngineBinaryData(data)
              }
          }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/4KjNe.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4KjNe.png" alt="enter image description here"></a></p>
  
  <p>thanks in advance!! </p>