foo -> UMethod (name = foo)
String -> USimpleNameReferenceExpression (identifier = String)
    s -> [!] UnknownKotlinExpression (PROPERTY)
    String -> USimpleNameReferenceExpression (identifier = String)
    s -> USimpleNameReferenceExpression (identifier = s)
    !! -> USimpleNameReferenceExpression (identifier = !!)
