Deprecate meaningless or vague-defined operations with Char operands: downTo.

libraries/tools/kotlin-stdlib-gen/src/generators/GenerateDownTos.kt

@@ -31,15 +31,21 @@ private fun generateDownTos(outputFile: File, header: String) {
             else -> "-1"
         }
 
+        val deprecated =
+        if ((fromType == "Char") != (toType == "Char")) {
+            """deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")"""
+        } else ""
+
         writer.println("""
 /**
  * Returns a progression from this value down to the specified [to] value.
  *
  * The [to] value has to be less than this value.
  */
+$deprecated
 public fun $fromType.downTo(to: $toType): $progressionType {
     return $progressionType($fromExpr, $toExpr, $incrementExpr)
-}""")
+}""".replace("\n\n","\n"))
     }
 
     println("Writing $outputFile")
@@ -53,7 +59,7 @@ public fun $fromType.downTo(to: $toType): $progressionType {
 $COMMON_AUTOGENERATED_WARNING
 """)
 
-        val types = array("Byte", "Char", "Short", "Int", "Long", "Float", "Double")
+        val types = arrayOf("Byte", "Char", "Short", "Int", "Long", "Float", "Double")
         for (fromType in types) {
             for (toType in types) {
                 generateDownTo(writer, fromType, toType)