We can not have any Token checker as colon. Since in case of colon we ensure no space before it and exactly one space after it.
for example 
```scala
val a: Int = 1 // valid
val b : Int = 1 //Invalid
val c:Int = 1 //Invalid
val c :Int = 1 //Invalid
```

Also there is a separate check for keywords. https://github.com/ScrapCodes/scalastyle/commit/cccb6b6d8e04521daa8af7e4f8c0e0bb35606f22