[FIR] Consider stability of receiver for DFA variables

^KT-57425 Fixed

compiler/testData/diagnostics/tests/smartCasts/publicVals/accessThrowOtherModule.kt

@@ -0,0 +1,14 @@
+// FIR_IDENTICAL
+// ISSUE: KT-57425
+// WITH_STDLIB
+
+data class Data(val x: Int?)
+
+fun test(pair: Pair<String?, Data>) {
+    if (pair.second.x != null) {
+        <!SMARTCAST_IMPOSSIBLE!>pair.second.x<!>.inc() // should be an error
+    }
+    if (pair.first != null) {
+        <!SMARTCAST_IMPOSSIBLE!>pair.first<!>.length // should be an error
+    }
+}