Minor: add regression test for KT-41806

compiler/testData/codegen/box/regressions/kt41806.kt

@@ -0,0 +1,26 @@
+// TARGET_BACKEND: JVM
+// WITH_RUNTIME
+// IGNORE_BACKEND_FIR: JVM_IR
+
+open class A {
+    fun Foo() {
+        print("Fop")
+    }
+}
+class B() : A()
+
+class C() : A()
+
+fun box(): String {
+    var test : A = B()
+
+    println((test as B).toString())
+
+    listOf(1,2 ,3).forEach { it ->
+        test = C()
+    }
+
+    test.Foo()
+
+    return "OK"
+}