[K/N][FIR] Do not emit CAST_NEVER_SUCCEEDS when casting to forward declarations

^KT-61841 Fixed

compiler/fir/checkers/checkers.native/src/org/jetbrains/kotlin/fir/analysis/native/checkers/FirNativeCastChecker.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2010-2024 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.fir.analysis.native.checkers
+
+import org.jetbrains.kotlin.fir.FirPlatformSpecificCastChecker
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
+import org.jetbrains.kotlin.fir.types.toRegularClassSymbol
+
+object FirNativeCastChecker : FirPlatformSpecificCastChecker() {
+    override fun shouldSuppressImpossibleCast(session: FirSession, fromType: ConeKotlinType, toType: ConeKotlinType): Boolean {
+        return isCastToAForwardDeclaration(session, toType)
+    }
+
+    /**
+     * Here, we only check that we are casting to a forward declaration to suppress a CAST_NEVER_SUCCEEDS warning.
+     * The cast would be further checked with FirNativeForwardDeclarationTypeOperatorChecker and FirNativeForwardDeclarationGetClassCallChecker.
+     */
+    private fun isCastToAForwardDeclaration(session: FirSession, forwardDeclarationType: ConeKotlinType): Boolean {
+        return forwardDeclarationType.toRegularClassSymbol(session)?.forwardDeclarationKindOrNull() != null
+    }
+}

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirCastOperatorsChecker.kt

@@ -16,10 +16,9 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.expressions.FirOperation
 import org.jetbrains.kotlin.fir.expressions.FirTypeOperatorCall
 import org.jetbrains.kotlin.fir.expressions.unwrapSmartcastExpression
+import org.jetbrains.kotlin.fir.firPlatformSpecificCastChecker
 import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
-import org.jetbrains.kotlin.fir.types.ConeDynamicType
-import org.jetbrains.kotlin.fir.types.coneType
-import org.jetbrains.kotlin.fir.types.resolvedType
+import org.jetbrains.kotlin.fir.types.*
 
 object FirCastOperatorsChecker : FirTypeOperatorCallChecker() {
     override fun check(expression: FirTypeOperatorCall, context: CheckerContext, reporter: DiagnosticReporter) {
@@ -38,7 +37,9 @@ object FirCastOperatorsChecker : FirTypeOperatorCallChecker() {
             val castType = checkCasting(actualType, targetType, isSafeAs, context)
             if (castType == CastingType.Impossible) {
                 if (context.languageVersionSettings.supportsFeature(LanguageFeature.EnableDfaWarningsInK2)) {
-                    reporter.reportOn(expression.source, FirErrors.CAST_NEVER_SUCCEEDS, context)
+                    if (!session.firPlatformSpecificCastChecker.shouldSuppressImpossibleCast(session, actualType, targetType)) {
+                        reporter.reportOn(expression.source, FirErrors.CAST_NEVER_SUCCEEDS, context)
+                    }
                 }
             } else if (castType == CastingType.Always) {
                 if (context.languageVersionSettings.supportsFeature(LanguageFeature.EnableDfaWarningsInK2)) {

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/ComponentsContainers.kt

@@ -95,6 +95,7 @@ fun FirSession.registerCommonComponents(languageVersionSettings: LanguageVersion
     register(FirPrimaryConstructorSuperTypeCheckerPlatformComponent::class, FirPrimaryConstructorSuperTypeCheckerPlatformComponent.Default)
     register(FirGenericArrayClassLiteralSupport::class, FirGenericArrayClassLiteralSupport.Disabled)
     register(FirMissingDependencyStorage::class, FirMissingDependencyStorage(this))
+    register(FirPlatformSpecificCastChecker::class, FirPlatformSpecificCastChecker.Default)
 }
 
 @OptIn(SessionConfiguration::class)

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/FirNativeSessionFactory.kt

@@ -6,10 +6,8 @@
 package org.jetbrains.kotlin.fir.session
 
 import org.jetbrains.kotlin.config.LanguageVersionSettings
-import org.jetbrains.kotlin.fir.BinaryModuleData
-import org.jetbrains.kotlin.fir.FirModuleData
-import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.SessionConfiguration
+import org.jetbrains.kotlin.fir.*
+import org.jetbrains.kotlin.fir.analysis.native.checkers.FirNativeCastChecker
 import org.jetbrains.kotlin.fir.backend.native.FirNativeClassMapper
 import org.jetbrains.kotlin.fir.checkers.registerNativeCheckers
 import org.jetbrains.kotlin.fir.deserialization.ModuleDataProvider
@@ -44,6 +42,7 @@ object FirNativeSessionFactory : FirAbstractSessionFactory() {
             registerExtraComponents = { session ->
                 session.registerDefaultComponents()
                 session.register(FirPlatformClassMapper::class, FirNativeClassMapper())
+                session.register(FirPlatformSpecificCastChecker::class, FirNativeCastChecker)
                 registerExtraComponents(session)
             },
             createKotlinScopeProvider = { FirKotlinScopeProvider() },
@@ -90,6 +89,7 @@ object FirNativeSessionFactory : FirAbstractSessionFactory() {
             registerExtraComponents = {
                 it.registerDefaultComponents()
                 it.register(FirPlatformClassMapper::class, FirNativeClassMapper())
+                it.register(FirPlatformSpecificCastChecker::class, FirNativeCastChecker)
                 registerExtraComponents(it)
             },
             registerExtraCheckers = { it.registerNativeCheckers() },

compiler/fir/entrypoint/src/org/jetbrains/kotlin/fir/session/FirSessionFactoryHelper.kt

@@ -140,5 +140,6 @@ object FirSessionFactoryHelper {
         register(FirPlatformClassMapper::class, FirPlatformClassMapper.Default)
         register(FirOverridesBackwardCompatibilityHelper::class, FirDefaultOverridesBackwardCompatibilityHelper)
         register(FirDelegatedMembersFilter::class, FirDelegatedMembersFilter.Default)
+        register(FirPlatformSpecificCastChecker::class, FirPlatformSpecificCastChecker.Default)
     }
 }

compiler/fir/providers/src/org/jetbrains/kotlin/fir/FirPlatformSpecificCastChecker.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2010-2024 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.fir
+
+import org.jetbrains.kotlin.fir.types.ConeKotlinType
+
+abstract class FirPlatformSpecificCastChecker : FirSessionComponent {
+    abstract fun shouldSuppressImpossibleCast(session: FirSession, fromType: ConeKotlinType, toType: ConeKotlinType): Boolean
+
+    object Default : FirPlatformSpecificCastChecker() {
+        override fun shouldSuppressImpossibleCast(session: FirSession, fromType: ConeKotlinType, toType: ConeKotlinType): Boolean {
+            return false
+        }
+    }
+}
+
+val FirSession.firPlatformSpecificCastChecker: FirPlatformSpecificCastChecker by FirSession.sessionComponentAccessor()

native/native.tests/tests/org/jetbrains/kotlin/konan/test/diagnostics/AbstractDiagnosticsNativeTest.kt

@@ -115,6 +115,10 @@ abstract class AbstractFirNativeDiagnosticsTestBase(val parser: FirParser) : Abs
             forTestsMatching("compiler/testData/diagnostics/*") {
                 configurationForClassicAndFirTestsAlongside()
             }
+
+            defaultDirectives {
+                LanguageSettingsDirectives.LANGUAGE + "+EnableDfaWarningsInK2"
+            }
         }
     }
 }