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

libraries/stdlib/src/generated/_DownTo.kt

@@ -20,6 +20,7 @@ public fun Byte.downTo(to: Byte): ByteProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Byte.downTo(to: Char): CharProgression {
     return CharProgression(this.toChar(), to, -1)
 }
@@ -74,6 +75,7 @@ public fun Byte.downTo(to: Double): DoubleProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Char.downTo(to: Byte): CharProgression {
     return CharProgression(this, to.toChar(), -1)
 }
@@ -92,6 +94,7 @@ public fun Char.downTo(to: Char): CharProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Char.downTo(to: Short): ShortProgression {
     return ShortProgression(this.toShort(), to, -1)
 }
@@ -101,6 +104,7 @@ public fun Char.downTo(to: Short): ShortProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Char.downTo(to: Int): IntProgression {
     return IntProgression(this.toInt(), to, -1)
 }
@@ -110,6 +114,7 @@ public fun Char.downTo(to: Int): IntProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Char.downTo(to: Long): LongProgression {
     return LongProgression(this.toLong(), to, -1.toLong())
 }
@@ -119,6 +124,7 @@ public fun Char.downTo(to: Long): LongProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Char.downTo(to: Float): FloatProgression {
     return FloatProgression(this.toFloat(), to, -1.toFloat())
 }
@@ -128,6 +134,7 @@ public fun Char.downTo(to: Float): FloatProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Char.downTo(to: Double): DoubleProgression {
     return DoubleProgression(this.toDouble(), to, -1.0)
 }
@@ -146,6 +153,7 @@ public fun Short.downTo(to: Byte): ShortProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Short.downTo(to: Char): ShortProgression {
     return ShortProgression(this, to.toShort(), -1)
 }
@@ -209,6 +217,7 @@ public fun Int.downTo(to: Byte): IntProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Int.downTo(to: Char): IntProgression {
     return IntProgression(this, to.toInt(), -1)
 }
@@ -272,6 +281,7 @@ public fun Long.downTo(to: Byte): LongProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Long.downTo(to: Char): LongProgression {
     return LongProgression(this, to.toLong(), -1.toLong())
 }
@@ -335,6 +345,7 @@ public fun Float.downTo(to: Byte): FloatProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Float.downTo(to: Char): FloatProgression {
     return FloatProgression(this, to.toFloat(), -1.toFloat())
 }
@@ -398,6 +409,7 @@ public fun Double.downTo(to: Byte): DoubleProgression {
  *
  * The [to] value has to be less than this value.
  */
+deprecated("This operation doesn't make sense and shall be removed in M13. Consider converting Char operand to Int or other operand to Char.")
 public fun Double.downTo(to: Char): DoubleProgression {
     return DoubleProgression(this, to.toDouble(), -1.0)
 }

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)