Verbose ClassCastException

runtime/src/main/cpp/Exceptions.h

@@ -39,7 +39,7 @@ void RUNTIME_NORETURN ThrowNullPointerException();
 // Context is evaluated from caller's address.
 void RUNTIME_NORETURN ThrowArrayIndexOutOfBoundsException();
 // Throws class cast exception.
-void RUNTIME_NORETURN ThrowClassCastException();
+void RUNTIME_NORETURN ThrowClassCastException(const ObjHeader* instance, const TypeInfo* type_info);
 // Throws arithmetic exception.
 void RUNTIME_NORETURN ThrowArithmeticException();
 // Throws number format exception.

runtime/src/main/cpp/Types.cpp

@@ -47,7 +47,7 @@ void CheckInstance(const ObjHeader* obj, const TypeInfo* type_info) {
   if (IsInstance(obj, type_info)) {
     return;
   }
-  ThrowClassCastException();
+  ThrowClassCastException(obj, type_info);
 }
 
 KBoolean Kotlin_TypeInfo_isInstance(KConstRef obj, KNativePtr typeInfo) {

runtime/src/main/kotlin/konan/internal/RuntimeUtils.kt

@@ -30,8 +30,9 @@ internal fun ThrowArrayIndexOutOfBoundsException(): Nothing {
 }
 
 @ExportForCppRuntime
-fun ThrowClassCastException(): Nothing {
+fun ThrowClassCastException(instance: Any, typeInfo: NativePtr): Nothing {
-    throw ClassCastException()
+    val clazz = KClassImpl<Any>(typeInfo)
+    throw ClassCastException("${instance::class.qualifiedName} cannot be cast to ${clazz.qualifiedName}")
 }
 
 fun ThrowTypeCastException(): Nothing {