FE: add one more test related to KT-56511 with the relevant feature ON

compiler/testData/diagnostics/tests/smartCasts/smartCastOnAlienPropertyFromInvisibleClass.fir.kt

@@ -0,0 +1,25 @@
+// !LANGUAGE: -ProhibitSmartcastsOnPropertyFromAlienBaseClassInheritedInInvisibleClass
+// RENDER_DIAGNOSTICS_FULL_TEXT
+// MODULE: m1
+// FILE: A.kt
+
+open class Base(val x: Any)
+
+// MODULE: m2(m1)
+// FILE: B.kt
+
+private class Derived : Base("123") {
+    fun foo() {
+        if (x is String) {
+            <!SMARTCAST_IMPOSSIBLE!>x<!>.length
+        }
+    }
+}
+
+internal class Internal : Base("456")
+
+internal fun bar(i: Internal) {
+    if (i.x is String) {
+        <!SMARTCAST_IMPOSSIBLE!>i.x<!>.length
+    }
+}