Don't emit CAST_NEVER_SUCCEEDS when casting to a forward declaration type

^KT-58929

compiler/frontend/src/org/jetbrains/kotlin/resolve/PlatformConfiguratorBase.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.resolve
 
+import org.jetbrains.kotlin.builtins.PlatformSpecificCastChecker
 import org.jetbrains.kotlin.builtins.PlatformToKotlinClassMapper
 import org.jetbrains.kotlin.container.*
 import org.jetbrains.kotlin.resolve.calls.checkers.*
@@ -128,6 +129,7 @@ abstract class PlatformConfiguratorBase(
     private val identifierChecker: IdentifierChecker? = null,
     private val overloadFilter: OverloadFilter? = null,
     private val platformToKotlinClassMapper: PlatformToKotlinClassMapper? = null,
+    private val platformSpecificCastChecker: PlatformSpecificCastChecker? = null,
     private val delegationFilter: DelegationFilter? = null,
     private val overridesBackwardCompatibilityHelper: OverridesBackwardCompatibilityHelper? = null,
     private val declarationReturnTypeSanitizer: DeclarationReturnTypeSanitizer? = null
@@ -154,6 +156,7 @@ abstract class PlatformConfiguratorBase(
             useInstanceIfNotNull(identifierChecker)
             useInstanceIfNotNull(overloadFilter)
             useInstanceIfNotNull(platformToKotlinClassMapper)
+            useInstanceIfNotNull(platformSpecificCastChecker)
             useInstanceIfNotNull(delegationFilter)
             useInstanceIfNotNull(overridesBackwardCompatibilityHelper)
             useInstanceIfNotNull(declarationReturnTypeSanitizer)

compiler/frontend/src/org/jetbrains/kotlin/types/CastDiagnosticsUtil.kt

@@ -19,6 +19,7 @@ package org.jetbrains.kotlin.types
 import com.google.common.collect.Maps
 import com.intellij.psi.util.PsiTreeUtil
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
+import org.jetbrains.kotlin.builtins.PlatformSpecificCastChecker
 import org.jetbrains.kotlin.builtins.PlatformToKotlinClassMapper
 import org.jetbrains.kotlin.builtins.isExtensionFunctionType
 import org.jetbrains.kotlin.builtins.isFunctionType
@@ -41,11 +42,12 @@ object CastDiagnosticsUtil {
     fun isCastPossible(
         lhsType: KotlinType,
         rhsType: KotlinType,
-        platformToKotlinClassMapper: PlatformToKotlinClassMapper
+        platformToKotlinClassMapper: PlatformToKotlinClassMapper,
+        platformSpecificCastChecker: PlatformSpecificCastChecker
     ): Boolean {
         val typeConstructor = lhsType.constructor
         if (typeConstructor is IntersectionTypeConstructor) {
-            return typeConstructor.supertypes.any { isCastPossible(it, rhsType, platformToKotlinClassMapper) }
+            return typeConstructor.supertypes.any { isCastPossible(it, rhsType, platformToKotlinClassMapper, platformSpecificCastChecker) }
         }
         val rhsNullable = TypeUtils.isNullableType(rhsType)
         val lhsNullable = TypeUtils.isNullableType(lhsType)
@@ -59,6 +61,7 @@ object CastDiagnosticsUtil {
         // This is an oversimplification (which does not render the method incomplete):
         // we consider any type parameter capable of taking any value, which may be made more precise if we considered bounds
         if (TypeUtils.isTypeParameter(lhsType) || TypeUtils.isTypeParameter(rhsType)) return true
+        if (platformSpecificCastChecker.isCastPossible(lhsType, rhsType)) return true
 
         if (isFinal(lhsType) || isFinal(rhsType)) return false
         if (isTrait(lhsType) || isTrait(rhsType)) return true

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java

@@ -376,7 +376,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
             return;
         }
 
-        if (!TypeUtilsKt.isStubType(actualType) && !CastDiagnosticsUtil.isCastPossible(actualType, targetType, components.platformToKotlinClassMapper)) {
+        if (!TypeUtilsKt.isStubType(actualType) && !CastDiagnosticsUtil.isCastPossible(actualType, targetType, components.platformToKotlinClassMapper, components.platformSpecificCastChecker)) {
             context.trace.report(CAST_NEVER_SUCCEEDS.on(expression.getOperationReference()));
             return;
         }

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/ExpressionTypingComponents.java

@@ -7,6 +7,7 @@ package org.jetbrains.kotlin.types.expressions;
 
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
+import org.jetbrains.kotlin.builtins.PlatformSpecificCastChecker;
 import org.jetbrains.kotlin.builtins.PlatformToKotlinClassMapper;
 import org.jetbrains.kotlin.config.LanguageVersionSettings;
 import org.jetbrains.kotlin.context.GlobalContext;
@@ -36,6 +37,7 @@ public class ExpressionTypingComponents {
     public ExpressionTypingServices expressionTypingServices;
     public CallResolver callResolver;
     public PlatformToKotlinClassMapper platformToKotlinClassMapper;
+    public PlatformSpecificCastChecker platformSpecificCastChecker;
     public ControlStructureTypingUtils controlStructureTypingUtils;
     public ForLoopConventionsChecker forLoopConventionsChecker;
     public FakeCallResolver fakeCallResolver;
@@ -100,6 +102,11 @@ public class ExpressionTypingComponents {
         this.platformToKotlinClassMapper = platformToKotlinClassMapper;
     }
 
+    @Inject
+    public void setPlatformToKotlinClassMap(@NotNull PlatformSpecificCastChecker platformSpecificCastChecker) {
+        this.platformSpecificCastChecker = platformSpecificCastChecker;
+    }
+
     @Inject
     public void setControlStructureTypingUtils(@NotNull ControlStructureTypingUtils controlStructureTypingUtils) {
         this.controlStructureTypingUtils = controlStructureTypingUtils;

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/PatternMatchingTypingVisitor.kt

@@ -678,7 +678,7 @@ class PatternMatchingTypingVisitor internal constructor(facade: ExpressionTyping
                 .takeIf { it.isNotEmpty() }
                 ?: possibleTypes
 
-            if (nonTrivialTypes.none { CastDiagnosticsUtil.isCastPossible(it, targetType, components.platformToKotlinClassMapper) }) {
+            if (nonTrivialTypes.none { CastDiagnosticsUtil.isCastPossible(it, targetType, components.platformToKotlinClassMapper, components.platformSpecificCastChecker) }) {
                 context.trace.report(USELESS_IS_CHECK.on(isCheck, negated))
             }
         }

compiler/testData/diagnostics/nativeTests/forwardDeclarations.kt

@@ -92,15 +92,15 @@ fun testInline4() {
     val c : (objcnames.protocols.FwdProtocol) -> Unit = ::<!FORWARD_DECLARATION_AS_REIFIED_TYPE_ARGUMENT!>inlineF<!>
 }
 
-fun testCheckedAs1(x : lib.FwdStruct) = x <!CAST_NEVER_SUCCEEDS!>as<!> cnames.structs.FwdStruct
+fun testCheckedAs1(x : lib.FwdStruct) = x as cnames.structs.FwdStruct
-fun testCheckedAs2(x : lib.FwdObjcClass) = x <!CAST_NEVER_SUCCEEDS!>as<!> objcnames.classes.FwdObjcClass
+fun testCheckedAs2(x : lib.FwdObjcClass) = x as objcnames.classes.FwdObjcClass
 fun testCheckedAs3(x : lib.FwdProtocol) = x as objcnames.protocols.FwdProtocol
-fun testCheckedSafeAs4(x : lib.FwdStruct) = x <!CAST_NEVER_SUCCEEDS!>as?<!> cnames.structs.FwdStruct
+fun testCheckedSafeAs4(x : lib.FwdStruct) = x as? cnames.structs.FwdStruct
-fun testCheckedSafeAs5(x : lib.FwdObjcClass) = x <!CAST_NEVER_SUCCEEDS!>as?<!> objcnames.classes.FwdObjcClass
+fun testCheckedSafeAs5(x : lib.FwdObjcClass) = x as? objcnames.classes.FwdObjcClass
 fun testCheckedSafeAs6(x : lib.FwdProtocol) = x as? objcnames.protocols.FwdProtocol
 
-fun testUnCheckedAs1(x : lib2.FwdStruct) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x <!CAST_NEVER_SUCCEEDS!>as<!> cnames.structs.FwdStruct<!>
+fun testUnCheckedAs1(x : lib2.FwdStruct) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x as cnames.structs.FwdStruct<!>
-fun testUnCheckedAs2(x : lib2.FwdObjcClass) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x <!CAST_NEVER_SUCCEEDS!>as<!> objcnames.classes.FwdObjcClass<!>
+fun testUnCheckedAs2(x : lib2.FwdObjcClass) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x as objcnames.classes.FwdObjcClass<!>
 fun testUnCheckedAs3(x : lib2.FwdProtocol) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x as objcnames.protocols.FwdProtocol<!>
 
-fun testUnCheckedAs4(x : lib.FwdStruct) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x <!CAST_NEVER_SUCCEEDS!>as<!> objcnames.classes.FwdObjcClass<!>
+fun testUnCheckedAs4(x : lib.FwdStruct) = <!UNCHECKED_CAST_TO_FORWARD_DECLARATION!>x as objcnames.classes.FwdObjcClass<!>

core/descriptors/src/org/jetbrains/kotlin/builtins/PlatformSpecificCastChecker.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+package org.jetbrains.kotlin.builtins
+
+import org.jetbrains.kotlin.container.DefaultImplementation
+import org.jetbrains.kotlin.types.KotlinType
+
+@DefaultImplementation(impl = PlatformSpecificCastChecker.Default::class)
+interface PlatformSpecificCastChecker {
+    fun isCastPossible(fromType: KotlinType, toType: KotlinType): Boolean
+
+    class Default : PlatformSpecificCastChecker {
+        override fun isCastPossible(fromType: KotlinType, toType: KotlinType): Boolean {
+            return false
+        }
+    }
+}

native/frontend/src/org/jetbrains/kotlin/resolve/konan/diagnostics/NativePlatformSpecificCastChecker.kt

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.resolve.konan.diagnostics
+
+import org.jetbrains.kotlin.builtins.PlatformSpecificCastChecker
+import org.jetbrains.kotlin.descriptors.ClassDescriptor
+import org.jetbrains.kotlin.descriptors.konan.getForwardDeclarationKindOrNull
+import org.jetbrains.kotlin.types.KotlinType
+
+object NativePlatformSpecificCastChecker : PlatformSpecificCastChecker {
+    override fun isCastPossible(fromType: KotlinType, toType: KotlinType): Boolean {
+        return isCastToAForwardDeclaration(toType)
+    }
+
+    /**
+     * Here, we only check that we are casting to a forward declaration to suppress a CAST_NEVER_SUCCEEDS warning. The cast is further
+     * checked in NativeForwardDeclarationRttiChecker.
+     */
+    private fun isCastToAForwardDeclaration(forwardDeclarationType: KotlinType): Boolean {
+        val forwardDeclarationClassDescriptor = forwardDeclarationType.constructor.declarationDescriptor
+        if (forwardDeclarationClassDescriptor !is ClassDescriptor) return false
+        return forwardDeclarationClassDescriptor.getForwardDeclarationKindOrNull() != null
+    }
+
+}

native/frontend/src/org/jetbrains/kotlin/resolve/konan/platform/NativePlatformConfigurator.kt

@@ -30,7 +30,8 @@ object NativePlatformConfigurator : PlatformConfiguratorBase(
         NativeObjCNameChecker, NativeObjCNameOverridesChecker,
         NativeObjCRefinementChecker, NativeObjCRefinementAnnotationChecker,
         NativeObjCRefinementOverridesChecker, NativeHiddenFromObjCInheritanceChecker,
-    )
+    ),
+    platformSpecificCastChecker = NativePlatformSpecificCastChecker
 ) {
     override fun configureModuleComponents(container: StorageComponentContainer) {
         container.useInstance(NativeInliningRule)