[FIR2IR] Keep redundant cast on 'this' for local anonymous function

#KT-42517 Fixed

compiler/testData/codegen/box/smartCasts/kt42517.kt

@@ -0,0 +1,19 @@
+// WITH_RUNTIME
+// FULL_JDK
+// IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS
+
+fun Any.copyValueIfNeeded(): Any {
+    return when (this) {
+        is Array<*> -> java.lang.reflect.Array.newInstance(this::class.java.componentType, size).apply {
+            this as Array<Any?>
+            (this@copyValueIfNeeded as Array<Any?>).forEachIndexed { i, value -> this[i] = value?.copyValueIfNeeded() }
+        }
+        else -> this
+    }
+}
+
+fun box(): String {
+    val res = arrayOf("FAIL", "OK").copyValueIfNeeded() as Array<String>
+    return res[1]
+}