Ensure ForLoopsLowering only handles the CharSequence.iterator()

extension function from the standard library (kotlin.text.iterator()).

compiler/testData/codegen/box/ranges/forInCharSequenceWithCustomIterator.kt

@@ -0,0 +1,65 @@
+// KJS_WITH_FULL_RUNTIME
+// WITH_RUNTIME
+import kotlin.test.*
+
+open class CharSequenceWithExtensionIterator(val s: String) : CharSequence {
+    fun get(foo: String): Char = TODO("shouldn't be called!")
+    override val length = s.length
+    override fun subSequence(startIndex: Int, endIndex: Int) = s.subSequence(startIndex, endIndex)
+    override fun get(index: Int) = s.get(index)
+}
+
+// Returns no characters
+operator fun CharSequenceWithExtensionIterator.iterator() = object : CharIterator() {
+    public override fun nextChar() = TODO()
+    public override fun hasNext() = false
+}
+
+class CharSequenceWithMemberIterator(s: String) : CharSequenceWithExtensionIterator(s) {
+    // Returns characters in reverse
+    operator fun iterator() = object : CharIterator() {
+        private var index = 0
+        public override fun nextChar() = get(length - ++index)
+        public override fun hasNext() = index < length
+    }
+}
+
+fun collectChars(cs: CharSequence): String {
+    val result = StringBuilder()
+    for (c in cs) {
+        result.append(c)
+    }
+    return result.toString()
+}
+
+fun <T : CharSequence> collectCharsTypeParam(cs: T): String {
+    val result = StringBuilder()
+    for (c in cs) {
+        result.append(c)
+    }
+    return result.toString()
+}
+
+fun box(): String {
+    val csWithExtIt = CharSequenceWithExtensionIterator("1234")
+    val csWithExtItResult = StringBuilder()
+    for (c in csWithExtIt) {
+        csWithExtItResult.append(c)
+    }
+    assertEquals("", csWithExtItResult.toString())
+
+    val csWithMemIt = CharSequenceWithMemberIterator("1234")
+    val csWithMemItResult = StringBuilder()
+    for (c in csWithMemIt) {
+        csWithMemItResult.append(c)
+    }
+    assertEquals("4321", csWithMemItResult.toString())
+
+    // The CharSequence.iterator() extension method should be invoked in all the following calls
+    assertEquals("1234", collectChars(csWithExtIt))
+    assertEquals("1234", collectCharsTypeParam(csWithExtIt))
+    assertEquals("1234", collectChars(csWithMemIt))
+    assertEquals("1234", collectCharsTypeParam(csWithMemIt))
+
+    return "OK"
+}