Setter parameter type always matches the property type, so it's not required to be explicit. The 'Remove explicit type specification' quick-fix allows amending the code accordingly.

Examples:

  fun process(x: Int) {}

  var x: Int = 0
      set(value: Int) = process(value) // <== 'Int' specification can be safely omitted

After the quick-fix is applied:

  fun process(x: Int) {}

  var x: Int = 0
      set(value) = process(value)