Deprecate Char-to-Number conversions in stdlib (JVM and JS)

- Int.toChar was left non-deprecated because the replacement is not intrinsic yet.
- Number.toChar was left non-deprecated because otherwise the deprecation propagates to the override, Int.toChar.

KT-23451

generators/builtins/primitives.kt

@@ -394,10 +394,14 @@ class GeneratePrimitives(out: PrintWriter) : BuiltInsSourceGenerator(out) {
     }
 
     private fun generateConversions(kind: PrimitiveType) {
-        fun isConversionDeprecated(otherKind: PrimitiveType): Boolean {
+        fun isFpToIntConversionDeprecated(otherKind: PrimitiveType): Boolean {
             return kind in PrimitiveType.floatingPoint && otherKind in listOf(PrimitiveType.BYTE, PrimitiveType.SHORT)
         }
 
+        fun isCharConversionDeprecated(otherKind: PrimitiveType): Boolean {
+            return kind != PrimitiveType.INT && otherKind == PrimitiveType.CHAR
+        }
+
         val thisName = kind.capitalized
         for (otherKind in PrimitiveType.exceptBoolean) {
             val otherName = otherKind.capitalized
@@ -422,10 +426,14 @@ class GeneratePrimitives(out: PrintWriter) : BuiltInsSourceGenerator(out) {
             }
             out.println(doc)
 
-            if (isConversionDeprecated(otherKind)) {
+            if (isFpToIntConversionDeprecated(otherKind)) {
                 out.println("    @Deprecated(\"Unclear conversion. To achieve the same result convert to Int explicitly and then to $otherName.\", ReplaceWith(\"toInt().to$otherName()\"))")
                 out.println("    @DeprecatedSinceKotlin(warningSince = \"1.3\", errorSince = \"1.5\")")
             }
+            if (isCharConversionDeprecated(otherKind)) {
+                out.println("    @Deprecated(\"Direct conversion to Char is deprecated. Use toInt().toChar() or Char constructor instead.\", ReplaceWith(\"this.toInt().toChar()\"))")
+                out.println("    @DeprecatedSinceKotlin(warningSince = \"1.5\")")
+            }
 
             out.println("    public override fun to$otherName(): $otherName")
         }

generators/builtins/progressionIterators.kt

@@ -27,7 +27,7 @@ fun integerProgressionIterator(kind: ProgressionKind): String {
     val incrementType = progressionIncrementType(kind)
 
     val (toInt, toType) = when (kind) {
-        CHAR -> ".toInt()" to ".to$t()"
+        CHAR -> ".code" to ".toChar()"
         else -> "" to ""
     }
 
@@ -36,9 +36,9 @@ fun integerProgressionIterator(kind: ProgressionKind): String {
  * @property step the number by which the value is incremented on each step.
  */
 internal class ${t}ProgressionIterator(first: $t, last: $t, val step: $incrementType) : ${t}Iterator() {
-    private val finalElement = last$toInt
+    private val finalElement: $incrementType = last$toInt
     private var hasNext: Boolean = if (step > 0) first <= last else first >= last
-    private var next = if (hasNext) first$toInt else finalElement
+    private var next: $incrementType = if (hasNext) first$toInt else finalElement
 
     override fun hasNext(): Boolean = hasNext
 

generators/builtins/progressions.kt

@@ -42,12 +42,20 @@ class GenerateProgressions(out: PrintWriter) : BuiltInsSourceGenerator(out) {
 
         val hashCode = "=\n" + when (kind) {
             CHAR ->
-                "        if (isEmpty()) -1 else (31 * (31 * first.toInt() + last.toInt()) + step)"
+                "        if (isEmpty()) -1 else (31 * (31 * first.code + last.code) + step)"
             INT ->
                 "        if (isEmpty()) -1 else (31 * (31 * first + last) + step)"
             LONG ->
                 "        if (isEmpty()) -1 else (31 * (31 * ${hashLong("first")} + ${hashLong("last")}) + ${hashLong("step")}).toInt()"
         }
+        val elementToIncrement = when (kind) {
+            CHAR -> ".code"
+            else -> ""
+        }
+        val incrementToElement = when (kind) {
+            CHAR -> ".toChar()"
+            else -> ""
+        }
 
         out.println(
                 """/**
@@ -73,7 +81,7 @@ public open class $progression
     /**
      * The last element in the progression.
      */
-    public val last: $t = getProgressionLastElement(start.to$incrementType(), endInclusive.to$incrementType(), step).to$t()
+    public val last: $t = getProgressionLastElement(start$elementToIncrement, endInclusive$elementToIncrement, step)$incrementToElement
 
     /**
      * The step of the progression.

generators/builtins/ranges.kt

@@ -39,7 +39,7 @@ class GenerateRanges(out: PrintWriter) : BuiltInsSourceGenerator(out) {
 
             val hashCode = when (kind) {
                 CHAR -> "=\n" +
-                "        if (isEmpty()) -1 else (31 * first.toInt() + last.toInt())"
+                "        if (isEmpty()) -1 else (31 * first.code + last.code)"
                 INT -> "=\n" +
                 "        if (isEmpty()) -1 else (31 * first + last)"
                 LONG -> "=\n" +