Specify when the range is empty in KDoc

generators/builtins/progressions.kt

@@ -82,7 +82,12 @@ public open class $progression
 
     override fun iterator(): ${t}Iterator = ${t}ProgressionIterator(first, last, step)
 
-    /** Checks if the progression is empty. */
+    /**
+     * Checks if the progression is empty.
+     
+     * Progression with a positive step is empty if its first element is greater than the last element.
+     * Progression with a negative step is empty if its first element is less than the last element.
+     */
     public open fun isEmpty(): Boolean = if (step > 0) first > last else first < last
 
     override fun equals(other: Any?): Boolean =