diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
index a64d43f7c07..38ade7eae77 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt
@@ -976,25 +976,25 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
 
     interface OptInUsage : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = OptInUsage::class
-        val optInMarkerFqName: FqName
+        val optInMarkerClassId: ClassId
         val message: String
     }
 
     interface OptInUsageError : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = OptInUsageError::class
-        val optInMarkerFqName: FqName
+        val optInMarkerClassId: ClassId
         val message: String
     }
 
     interface OptInOverride : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = OptInOverride::class
-        val optInMarkerFqName: FqName
+        val optInMarkerClassId: ClassId
         val message: String
     }
 
     interface OptInOverrideError : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = OptInOverrideError::class
-        val optInMarkerFqName: FqName
+        val optInMarkerClassId: ClassId
         val message: String
     }
 
@@ -1016,7 +1016,7 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
 
     interface OptInArgumentIsNotMarker : KtFirDiagnostic<KtAnnotationEntry> {
         override val diagnosticClass get() = OptInArgumentIsNotMarker::class
-        val notMarkerFqName: FqName
+        val notMarkerClassId: ClassId
     }
 
     interface OptInMarkerWithWrongTarget : KtFirDiagnostic<KtAnnotationEntry> {
@@ -1799,7 +1799,7 @@ sealed interface KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
 
     interface PlatformClassMappedToKotlin : KtFirDiagnostic<PsiElement> {
         override val diagnosticClass get() = PlatformClassMappedToKotlin::class
-        val kotlinClass: FqName
+        val kotlinClass: ClassId
     }
 
     interface InferredTypeVariableIntoEmptyIntersectionError : KtFirDiagnostic<PsiElement> {
diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
index f90301ca61f..668dfbc7cbd 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
@@ -1170,28 +1170,28 @@ internal class WrongJsQualifierImpl(
 ) : KtAbstractFirDiagnostic<KtElement>(firDiagnostic, token), KtFirDiagnostic.WrongJsQualifier
 
 internal class OptInUsageImpl(
-    override val optInMarkerFqName: FqName,
+    override val optInMarkerClassId: ClassId,
     override val message: String,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KtFirDiagnostic.OptInUsage
 
 internal class OptInUsageErrorImpl(
-    override val optInMarkerFqName: FqName,
+    override val optInMarkerClassId: ClassId,
     override val message: String,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KtFirDiagnostic.OptInUsageError
 
 internal class OptInOverrideImpl(
-    override val optInMarkerFqName: FqName,
+    override val optInMarkerClassId: ClassId,
     override val message: String,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KtFirDiagnostic.OptInOverride
 
 internal class OptInOverrideErrorImpl(
-    override val optInMarkerFqName: FqName,
+    override val optInMarkerClassId: ClassId,
     override val message: String,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
@@ -1218,7 +1218,7 @@ internal class OptInWithoutArgumentsImpl(
 ) : KtAbstractFirDiagnostic<KtAnnotationEntry>(firDiagnostic, token), KtFirDiagnostic.OptInWithoutArguments
 
 internal class OptInArgumentIsNotMarkerImpl(
-    override val notMarkerFqName: FqName,
+    override val notMarkerClassId: ClassId,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<KtAnnotationEntry>(firDiagnostic, token), KtFirDiagnostic.OptInArgumentIsNotMarker
@@ -2161,7 +2161,7 @@ internal class RedundantNullableImpl(
 ) : KtAbstractFirDiagnostic<KtTypeReference>(firDiagnostic, token), KtFirDiagnostic.RedundantNullable
 
 internal class PlatformClassMappedToKotlinImpl(
-    override val kotlinClass: FqName,
+    override val kotlinClass: ClassId,
     firDiagnostic: KtPsiDiagnostic,
     token: KtLifetimeToken,
 ) : KtAbstractFirDiagnostic<PsiElement>(firDiagnostic, token), KtFirDiagnostic.PlatformClassMappedToKotlin
diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
index 6fd2d40e1a7..a6110a4b8fc 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -30,7 +30,6 @@ import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.metadata.deserialization.VersionRequirement
 import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.ClassId
-import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.ForbiddenNamedArgumentsTarget
@@ -402,19 +401,19 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
 
     val OPT_IN by object : DiagnosticGroup("OptIn") {
         val OPT_IN_USAGE by warning<PsiElement>(PositioningStrategy.REFERENCE_BY_QUALIFIED) {
-            parameter<FqName>("optInMarkerFqName")
+            parameter<ClassId>("optInMarkerClassId")
             parameter<String>("message")
         }
         val OPT_IN_USAGE_ERROR by error<PsiElement>(PositioningStrategy.REFERENCE_BY_QUALIFIED) {
-            parameter<FqName>("optInMarkerFqName")
+            parameter<ClassId>("optInMarkerClassId")
             parameter<String>("message")
         }
         val OPT_IN_OVERRIDE by warning<PsiElement>(PositioningStrategy.DECLARATION_NAME) {
-            parameter<FqName>("optInMarkerFqName")
+            parameter<ClassId>("optInMarkerClassId")
             parameter<String>("message")
         }
         val OPT_IN_OVERRIDE_ERROR by error<PsiElement>(PositioningStrategy.DECLARATION_NAME) {
-            parameter<FqName>("optInMarkerFqName")
+            parameter<ClassId>("optInMarkerClassId")
             parameter<String>("message")
         }
 
@@ -424,7 +423,7 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
 
         val OPT_IN_WITHOUT_ARGUMENTS by warning<KtAnnotationEntry>()
         val OPT_IN_ARGUMENT_IS_NOT_MARKER by warning<KtAnnotationEntry> {
-            parameter<FqName>("notMarkerFqName")
+            parameter<ClassId>("notMarkerClassId")
         }
         val OPT_IN_MARKER_WITH_WRONG_TARGET by error<KtAnnotationEntry> {
             parameter<String>("target")
@@ -849,7 +848,7 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val REDUNDANT_NULLABLE by warning<KtTypeReference>(PositioningStrategy.REDUNDANT_NULLABLE)
 
         val PLATFORM_CLASS_MAPPED_TO_KOTLIN by warning<PsiElement>(PositioningStrategy.REFERENCED_NAME_BY_QUALIFIED) {
-            parameter<FqName>("kotlinClass")
+            parameter<ClassId>("kotlinClass")
         }
 
         val INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION by deprecationError<PsiElement>(
diff --git a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
index d3f5fd19bb5..f77d6f5f155 100644
--- a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
+++ b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
@@ -69,7 +69,6 @@ import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.metadata.deserialization.VersionRequirement.Version
 import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.ClassId
-import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.KtAnnotationEntry
 import org.jetbrains.kotlin.psi.KtAnonymousInitializer
@@ -311,15 +310,15 @@ object FirErrors {
     val POTENTIALLY_NON_REPORTED_ANNOTATION: KtDiagnosticFactory0 by warning0<KtAnnotationEntry>()
 
     // OptIn
-    val OPT_IN_USAGE: KtDiagnosticFactory2<FqName, String> by warning2<PsiElement, FqName, String>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)
-    val OPT_IN_USAGE_ERROR: KtDiagnosticFactory2<FqName, String> by error2<PsiElement, FqName, String>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)
-    val OPT_IN_OVERRIDE: KtDiagnosticFactory2<FqName, String> by warning2<PsiElement, FqName, String>(SourceElementPositioningStrategies.DECLARATION_NAME)
-    val OPT_IN_OVERRIDE_ERROR: KtDiagnosticFactory2<FqName, String> by error2<PsiElement, FqName, String>(SourceElementPositioningStrategies.DECLARATION_NAME)
+    val OPT_IN_USAGE: KtDiagnosticFactory2<ClassId, String> by warning2<PsiElement, ClassId, String>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)
+    val OPT_IN_USAGE_ERROR: KtDiagnosticFactory2<ClassId, String> by error2<PsiElement, ClassId, String>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)
+    val OPT_IN_OVERRIDE: KtDiagnosticFactory2<ClassId, String> by warning2<PsiElement, ClassId, String>(SourceElementPositioningStrategies.DECLARATION_NAME)
+    val OPT_IN_OVERRIDE_ERROR: KtDiagnosticFactory2<ClassId, String> by error2<PsiElement, ClassId, String>(SourceElementPositioningStrategies.DECLARATION_NAME)
     val OPT_IN_IS_NOT_ENABLED: KtDiagnosticFactory0 by warning0<KtAnnotationEntry>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)
     val OPT_IN_CAN_ONLY_BE_USED_AS_ANNOTATION: KtDiagnosticFactory0 by error0<PsiElement>()
     val OPT_IN_MARKER_CAN_ONLY_BE_USED_AS_ANNOTATION_OR_ARGUMENT_IN_OPT_IN: KtDiagnosticFactory0 by error0<PsiElement>()
     val OPT_IN_WITHOUT_ARGUMENTS: KtDiagnosticFactory0 by warning0<KtAnnotationEntry>()
-    val OPT_IN_ARGUMENT_IS_NOT_MARKER: KtDiagnosticFactory1<FqName> by warning1<KtAnnotationEntry, FqName>()
+    val OPT_IN_ARGUMENT_IS_NOT_MARKER: KtDiagnosticFactory1<ClassId> by warning1<KtAnnotationEntry, ClassId>()
     val OPT_IN_MARKER_WITH_WRONG_TARGET: KtDiagnosticFactory1<String> by error1<KtAnnotationEntry, String>()
     val OPT_IN_MARKER_WITH_WRONG_RETENTION: KtDiagnosticFactory0 by error0<KtAnnotationEntry>()
     val OPT_IN_MARKER_ON_WRONG_TARGET: KtDiagnosticFactory1<String> by error1<KtAnnotationEntry, String>()
@@ -489,7 +488,7 @@ object FirErrors {
     val TYPE_VARIANCE_CONFLICT_IN_EXPANDED_TYPE: KtDiagnosticFactory4<FirTypeParameterSymbol, Variance, Variance, ConeKotlinType> by error4<PsiElement, FirTypeParameterSymbol, Variance, Variance, ConeKotlinType>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
     val SMARTCAST_IMPOSSIBLE: KtDiagnosticFactory4<ConeKotlinType, FirExpression, String, Boolean> by error4<KtExpression, ConeKotlinType, FirExpression, String, Boolean>()
     val REDUNDANT_NULLABLE: KtDiagnosticFactory0 by warning0<KtTypeReference>(SourceElementPositioningStrategies.REDUNDANT_NULLABLE)
-    val PLATFORM_CLASS_MAPPED_TO_KOTLIN: KtDiagnosticFactory1<FqName> by warning1<PsiElement, FqName>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)
+    val PLATFORM_CLASS_MAPPED_TO_KOTLIN: KtDiagnosticFactory1<ClassId> by warning1<PsiElement, ClassId>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)
     val INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION: KtDiagnosticFactoryForDeprecation4<String, Collection<ConeKotlinType>, String, String> by deprecationError4<PsiElement, String, Collection<ConeKotlinType>, String, String>(ForbidInferringTypeVariablesIntoEmptyIntersection)
     val INFERRED_TYPE_VARIABLE_INTO_POSSIBLE_EMPTY_INTERSECTION: KtDiagnosticFactory4<String, Collection<ConeKotlinType>, String, String> by warning4<PsiElement, String, Collection<ConeKotlinType>, String, String>()
     val INCORRECT_LEFT_COMPONENT_OF_INTERSECTION: KtDiagnosticFactory0 by error0<KtTypeReference>()
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInAnnotationCallChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInAnnotationCallChecker.kt
index c297dd16b1a..59cf444778a 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInAnnotationCallChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInAnnotationCallChecker.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -10,13 +10,13 @@ import org.jetbrains.kotlin.config.AnalysisFlags
 import org.jetbrains.kotlin.config.LanguageFeature
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
-import org.jetbrains.kotlin.fir.analysis.checkers.extractClassesFromArgument
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.extractClassFromArgument
+import org.jetbrains.kotlin.fir.analysis.checkers.extractClassesFromArgument
 import org.jetbrains.kotlin.fir.analysis.checkers.modality
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.findArgumentByName
 import org.jetbrains.kotlin.fir.declarations.utils.isFun
@@ -102,7 +102,7 @@ object FirOptInAnnotationCallChecker : FirAnnotationCallChecker() {
                 reporter.reportOn(
                     source,
                     FirErrors.OPT_IN_ARGUMENT_IS_NOT_MARKER,
-                    classSymbol.classId.asSingleFqName(),
+                    classSymbol.classId,
                     context
                 )
             }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInUsageBaseChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInUsageBaseChecker.kt
index a1cc8b7736d..cd386389db1 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInUsageBaseChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirOptInUsageBaseChecker.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2022 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -303,10 +303,9 @@ object FirOptInUsageBaseChecker {
                     Experimentality.Severity.WARNING -> FirErrors.OPT_IN_USAGE to "should"
                     Experimentality.Severity.ERROR -> FirErrors.OPT_IN_USAGE_ERROR to "must"
                 }
-                val fqName = annotationClassId.asSingleFqName()
                 val reportedMessage = message?.takeIf { it.isNotBlank() }
-                    ?: OptInNames.buildDefaultDiagnosticMessage(OptInNames.buildMessagePrefix(verb), fqName.asString())
-                reporter.reportOn(source, diagnostic, fqName, reportedMessage, context)
+                    ?: OptInNames.buildDefaultDiagnosticMessage(OptInNames.buildMessagePrefix(verb), annotationClassId.asFqNameString())
+                reporter.reportOn(source, diagnostic, annotationClassId, reportedMessage, context)
             }
         }
     }
@@ -332,7 +331,7 @@ object FirOptInUsageBaseChecker {
                     verb,
                     markerName = annotationClassId.asFqNameString()
                 )
-                reporter.reportOn(symbol.source, diagnostic, annotationClassId.asSingleFqName(), message, context)
+                reporter.reportOn(symbol.source, diagnostic, annotationClassId, message, context)
             }
         }
     }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinImportsChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinImportsChecker.kt
index 01c44bedbd6..d47e8a48cc3 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinImportsChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinImportsChecker.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -27,7 +27,7 @@ object PlatformClassMappedToKotlinImportsChecker : FirFileChecker() {
 
             val kotlinClass = context.session.platformClassMapper.getCorrespondingKotlinClass(classId)
             if (kotlinClass != null) {
-                reporter.reportOn(import.source, FirErrors.PLATFORM_CLASS_MAPPED_TO_KOTLIN, importedFqName, context)
+                reporter.reportOn(import.source, FirErrors.PLATFORM_CLASS_MAPPED_TO_KOTLIN, classId, context)
             }
         }
     }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinTypeRefChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinTypeRefChecker.kt
index 77c83758a85..3e207c11e54 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinTypeRefChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/PlatformClassMappedToKotlinTypeRefChecker.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.
  */
 
@@ -20,7 +20,7 @@ object PlatformClassMappedToKotlinTypeRefChecker : FirTypeRefChecker() {
         if (typeRef is FirResolvedTypeRef && typeRef.source != null) {
             val kotlinClass = context.session.platformClassMapper.getCorrespondingKotlinClass(typeRef.type.classId)
             if (kotlinClass != null) {
-                reporter.reportOn(typeRef.source, FirErrors.PLATFORM_CLASS_MAPPED_TO_KOTLIN, kotlinClass.asSingleFqName(), context)
+                reporter.reportOn(typeRef.source, FirErrors.PLATFORM_CLASS_MAPPED_TO_KOTLIN, kotlinClass, context)
             }
         }
     }