K2: reproduce & add test for KT-56511

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/diagnostic/compiler/based/DiagnosisCompilerTestFE10TestdataTestGenerated.java

@@ -30180,6 +30180,12 @@ public class DiagnosisCompilerTestFE10TestdataTestGenerated extends AbstractDiag
                 runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastAndArgumentApproximation.kt");
             }
 
+            @Test
+            @TestMetadata("smartCastOnAlienPropertyFromInnerClass.kt")
+            public void testSmartCastOnAlienPropertyFromInnerClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastOnAlienPropertyFromInnerClass.kt");
+            }
+
             @Test
             @TestMetadata("smartCastOnElvis.kt")
             public void testSmartCastOnElvis() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java

@@ -30180,6 +30180,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                 runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastAndArgumentApproximation.kt");
             }
 
+            @Test
+            @TestMetadata("smartCastOnAlienPropertyFromInnerClass.kt")
+            public void testSmartCastOnAlienPropertyFromInnerClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastOnAlienPropertyFromInnerClass.kt");
+            }
+
             @Test
             @TestMetadata("smartCastOnElvis.kt")
             public void testSmartCastOnElvis() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java

@@ -30276,6 +30276,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                 runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastAndArgumentApproximation.kt");
             }
 
+            @Test
+            @TestMetadata("smartCastOnAlienPropertyFromInnerClass.kt")
+            public void testSmartCastOnAlienPropertyFromInnerClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastOnAlienPropertyFromInnerClass.kt");
+            }
+
             @Test
             @TestMetadata("smartCastOnElvis.kt")
             public void testSmartCastOnElvis() throws Exception {

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

@@ -0,0 +1,15 @@
+// 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
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/smartCastOnAlienPropertyFromInnerClass.kt

@@ -0,0 +1,15 @@
+// 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) {
+            <!DEBUG_INFO_SMARTCAST!>x<!>.length
+        }
+    }
+}

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/DiagnosticTestGenerated.java

@@ -30276,6 +30276,12 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastAndArgumentApproximation.kt");
             }
 
+            @Test
+            @TestMetadata("smartCastOnAlienPropertyFromInnerClass.kt")
+            public void testSmartCastOnAlienPropertyFromInnerClass() throws Exception {
+                runTest("compiler/testData/diagnostics/tests/smartCasts/smartCastOnAlienPropertyFromInnerClass.kt");
+            }
+
             @Test
             @TestMetadata("smartCastOnElvis.kt")
             public void testSmartCastOnElvis() throws Exception {