[K2] Prohibit smart casts for 'expect' properties

^KT-61340

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

@@ -1723,6 +1723,28 @@ public class FirOldFrontendMPPDiagnosticsWithLightTreeTestGenerated extends Abst
         }
     }
 
+    @Nested
+    @TestMetadata("compiler/testData/diagnostics/tests/multiplatform/smartCasts")
+    @TestDataPath("$PROJECT_ROOT")
+    public class SmartCasts {
+        @Test
+        public void testAllFilesPresentInSmartCasts() throws Exception {
+            KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests/multiplatform/smartCasts"), Pattern.compile("^(.*)\\.kts?$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), TargetBackend.JVM_IR, true);
+        }
+
+        @Test
+        @TestMetadata("kt61340_commonCode.kt")
+        public void testKt61340_commonCode() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_commonCode.kt");
+        }
+
+        @Test
+        @TestMetadata("kt61340_platformCode.kt")
+        public void testKt61340_platformCode() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_platformCode.kt");
+        }
+    }
+
     @Nested
     @TestMetadata("compiler/testData/diagnostics/tests/multiplatform/topLevelFun")
     @TestDataPath("$PROJECT_ROOT")

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

@@ -1723,6 +1723,28 @@ public class FirOldFrontendMPPDiagnosticsWithPsiTestGenerated extends AbstractFi
         }
     }
 
+    @Nested
+    @TestMetadata("compiler/testData/diagnostics/tests/multiplatform/smartCasts")
+    @TestDataPath("$PROJECT_ROOT")
+    public class SmartCasts {
+        @Test
+        public void testAllFilesPresentInSmartCasts() throws Exception {
+            KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests/multiplatform/smartCasts"), Pattern.compile("^(.*)\\.kts?$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), TargetBackend.JVM_IR, true);
+        }
+
+        @Test
+        @TestMetadata("kt61340_commonCode.kt")
+        public void testKt61340_commonCode() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_commonCode.kt");
+        }
+
+        @Test
+        @TestMetadata("kt61340_platformCode.kt")
+        public void testKt61340_platformCode() throws Exception {
+            runTest("compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_platformCode.kt");
+        }
+    }
+
     @Nested
     @TestMetadata("compiler/testData/diagnostics/tests/multiplatform/topLevelFun")
     @TestDataPath("$PROJECT_ROOT")

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/DfaVariables.kt

@@ -36,6 +36,9 @@ enum class PropertyStability(val impliedSmartcastStability: SmartcastStability?)
     // Smartcast may or may not be safe, depending on whether there are concurrent writes to this local variable.
     LOCAL_VAR(null),
 
+    // Smartcast is always unsafe regardless of usage.
+    EXPECT_PROPERTY(SmartcastStability.EXPECT_PROPERTY),
+
     // Open or custom getter.
     // Smartcast is always unsafe regardless of usage.
     PROPERTY_WITH_GETTER(SmartcastStability.PROPERTY_WITH_GETTER),

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/dfa/VariableStorageImpl.kt

@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.fir.declarations.FirAnonymousObject
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
 import org.jetbrains.kotlin.fir.declarations.impl.FirDefaultPropertyAccessor
+import org.jetbrains.kotlin.fir.declarations.utils.isExpect
 import org.jetbrains.kotlin.fir.declarations.utils.isFinal
 import org.jetbrains.kotlin.fir.declarations.utils.modality
 import org.jetbrains.kotlin.fir.declarations.utils.visibility
@@ -165,6 +166,7 @@ class VariableStorageImpl(private val session: FirSession) : VariableStorage() {
             is FirFunctionSymbol<*>, is FirClassSymbol<*> -> return PropertyStability.STABLE_VALUE
             is FirBackingFieldSymbol -> return if (isVal) PropertyStability.STABLE_VALUE else PropertyStability.MUTABLE_PROPERTY
         }
+        if (this is FirCallableSymbol && this.isExpect) return PropertyStability.EXPECT_PROPERTY
         if (this !is FirVariableSymbol<*>) return null
         if (this is FirFieldSymbol && !this.isFinal) return PropertyStability.MUTABLE_PROPERTY
 

compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_commonCode.fir.kt

@@ -0,0 +1,25 @@
+// !DIAGNOSTICS: -DEBUG_INFO_SMARTCAST
+// MODULE: m1-common
+// FILE: common.kt
+
+expect val foo: Any
+
+expect class Bar() {
+    val bus: Any
+}
+
+fun common() {
+    if (foo is String) <!SMARTCAST_IMPOSSIBLE!>foo<!>.length
+
+    val bar = Bar()
+    if (bar.bus is String) <!SMARTCAST_IMPOSSIBLE!>bar.bus<!>.length
+}
+
+// MODULE: m1-jvm()()(m1-common)
+// FILE: jvm.kt
+actual val foo: Any = 2
+
+actual class Bar actual constructor() {
+    actual val bus: Any
+        get() = "bus"
+}

compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_commonCode.kt

@@ -0,0 +1,25 @@
+// !DIAGNOSTICS: -DEBUG_INFO_SMARTCAST
+// MODULE: m1-common
+// FILE: common.kt
+
+expect val foo: Any
+
+expect class Bar() {
+    val bus: Any
+}
+
+fun common() {
+    if (foo is String) foo.length
+
+    val bar = Bar()
+    if (bar.bus is String) <!SMARTCAST_IMPOSSIBLE{JVM}!>bar.bus<!>.length
+}
+
+// MODULE: m1-jvm()()(m1-common)
+// FILE: jvm.kt
+actual val foo: Any = 2
+
+actual class Bar actual constructor() {
+    actual val bus: Any
+        get() = "bus"
+}

compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_platformCode.kt

@@ -0,0 +1,26 @@
+// FIR_IDENTICAL
+// !DIAGNOSTICS: -DEBUG_INFO_SMARTCAST
+// MODULE: m1-common
+// FILE: common.kt
+
+expect val foo: Any
+
+expect class Bar() {
+    val bus: Any
+}
+
+// MODULE: m1-jvm()()(m1-common)
+// FILE: jvm.kt
+actual val foo: Any = 2
+
+actual class Bar actual constructor() {
+    actual val bus: Any
+        get() = "bus"
+}
+
+fun platform() {
+    if (foo is String) foo.length
+
+    val bar = Bar()
+    if (bar.bus is String) <!SMARTCAST_IMPOSSIBLE!>bar.bus<!>.length
+}

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

@@ -24892,6 +24892,28 @@ public class DiagnosticTestGenerated extends AbstractDiagnosticTest {
                 }
             }
 
+            @Nested
+            @TestMetadata("compiler/testData/diagnostics/tests/multiplatform/smartCasts")
+            @TestDataPath("$PROJECT_ROOT")
+            public class SmartCasts {
+                @Test
+                public void testAllFilesPresentInSmartCasts() throws Exception {
+                    KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/diagnostics/tests/multiplatform/smartCasts"), Pattern.compile("^(.*)\\.kts?$"), Pattern.compile("^(.+)\\.(reversed|fir|ll)\\.kts?$"), true);
+                }
+
+                @Test
+                @TestMetadata("kt61340_commonCode.kt")
+                public void testKt61340_commonCode() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_commonCode.kt");
+                }
+
+                @Test
+                @TestMetadata("kt61340_platformCode.kt")
+                public void testKt61340_platformCode() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/multiplatform/smartCasts/kt61340_platformCode.kt");
+                }
+            }
+
             @Nested
             @TestMetadata("compiler/testData/diagnostics/tests/multiplatform/topLevelFun")
             @TestDataPath("$PROJECT_ROOT")

core/compiler.common/src/org/jetbrains/kotlin/types/SmartcastStability.kt

@@ -17,6 +17,9 @@ enum class SmartcastStability(private val str: String, val description: String =
     // Smart casts are completely safe
     STABLE_VALUE("stable val"),
 
+    // Smart casts are not safe
+    EXPECT_PROPERTY("expect property"),
+
     // Member value with open / custom getter
     // Smart casts are not safe
     PROPERTY_WITH_GETTER("custom getter", "property that has open or custom getter"),