Fix regionMatch for CharSequence

runtime/src/main/cpp/KString.cpp

@@ -981,13 +981,6 @@ KBoolean Kotlin_String_regionMatches(KString thiz, KInt thizOffset,
   return true;
 }
 
-KBoolean Kotlin_CharSequence_regionMatches(KString thiz, KInt thizOffset,
-                                           KString other, KInt otherOffset,
-                                           KInt length, KBoolean ignoreCase) {
-  return Kotlin_String_regionMatches(thiz, thizOffset, other, otherOffset,
-                                     length, ignoreCase);
-}
-
 KBoolean Kotlin_Char_isDefined(KChar ch) {
   // TODO: fixme!
   RuntimeAssert(false, "Kotlin_Char_isDefined() is not implemented");

runtime/src/main/kotlin/kotlin/text/Strings.kt

@@ -139,11 +139,15 @@ public fun String.endsWith(suffix: String, ignoreCase: Boolean = false): Boolean
  * @param otherOffset the start offset in the other char sequence of the substring to compare.
  * @param length the length of the substring to compare.
  */
-@SymbolName("Kotlin_CharSequence_regionMatches")
+public actual fun CharSequence.regionMatches(
-external public actual fun CharSequence.regionMatches(
         thisOffset: Int, other: CharSequence, otherOffset: Int, length: Int,
-        ignoreCase: Boolean): Boolean
+        ignoreCase: Boolean): Boolean {
-
+    return if (this is String && other is String) {
+        this.regionMatches(thisOffset, other, otherOffset, length, ignoreCase)
+    } else {
+        regionMatchesImpl(thisOffset, other, otherOffset, length, ignoreCase)
+    }
+}
 
 /**
  * Returns `true` if the specified range in this string is equal to the specified range in another string.