The TUnion copy constructor causes the editor to toss an assert due to it claiming that the passed in TUnion is of an Unrecognized TUnion subtype.
#include "Runtime/Core/Public/Containers/Union.h"
DEFINE_LOG_CATEGORY(LogUnion);
TUnion<int32, float> default_constructed; TUnion<int32, float> copy_constructed = default_constructed;
Unknown exception - code 00000001 (first/second chance not available) "Fatal error: [File:C:\Program Files\Epic Games\4.10\Engine\Source\Runtime//Core//Public//Containers//Union.h] [Line: 374] Unrecognized TUnion subtype " UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\core\private\misc\outputdevice.cpp:374] UE4Editor_MyProject4!TUnion<int,float,FNull,FNull,FNull,FNull>::FatalErrorUndefinedSubtype() [c:\program files\epic games\4.10\engine\source\runtime\core\public\containers\union.h:374] UE4Editor_MyProject4!AMyActor::BeginPlay() [c:\users\matthew.clark\documents\unreal projects\4.10\myproject4\source\myproject4\myactor.cpp:21] UE4Editor_Engine!AWorldSettings::NotifyBeginPlay() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\worldsettings.cpp:137] UE4Editor_Engine!AGameMode::HandleMatchHasStarted() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\gamemode.cpp:614] UE4Editor_Engine!AGameMode::SetMatchState() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\gamemode.cpp:730] UE4Editor_Engine!AGameMode::StartMatch() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\gamemode.cpp:591] UE4Editor_Engine!UWorld::BeginPlay() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\world.cpp:3082] UE4Editor_Engine!UGameInstance::StartPIEGameInstance() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\engine\private\gameinstance.cpp:274] UE4Editor_UnrealEd!UEditorEngine::CreatePIEGameInstance() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\unrealed\private\playlevel.cpp:3012] UE4Editor_UnrealEd!UEditorEngine::PlayInEditor() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\unrealed\private\playlevel.cpp:2259] UE4Editor_UnrealEd!UEditorEngine::StartQueuedPlayMapRequest() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\unrealed\private\playlevel.cpp:1048] UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\unrealed\private\editorengine.cpp:1244] UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\editor\unrealed\private\unrealedengine.cpp:361] UE4Editor!FEngineLoop::Tick() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\launchengineloop.cpp:2427] UE4Editor!GuardedMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\launch.cpp:142] UE4Editor!GuardedMainWrapper() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\windows\launchwindows.cpp:126] UE4Editor!WinMain() [d:\buildfarm\buildmachine_++depot+ue4-releases+4.10\engine\source\runtime\launch\private\windows\launchwindows.cpp:200] UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264] kernel32 ntdll
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