Someone else must have received this message while (or after) converting an iOS project to Swift 3, yet when I do a Google search, I get no relevant results.
Anyway,
In my case it was an issue related to a dictionary without explicit type:
let dict = ["key": value]
Than I solved specifying the type:
let dict: [String: Any] = ["key": value]
In your case you can specify your value type:
let dict: [String: UIView] = ["key": value]