Use of undeclared type 'GMSPlacesClient'

I have also face the same issue. To resolve this I have add pod GooglePlaces in my pod file and update the pod.

Also you need to replace import import GoogleMaps To import GooglePlaces

I found the problem. Google has divided his API in two parts. Last release splits the Places API from the Maps SDK (since Version 2.0.0 - July 26, 2016). You can find it in the release notes: https://developers.google.com/places/ios-api/releases?hl=es