Unreal Engine Issues and Bug Tracker (UE-42158)

Description

When an actor has an instanced blueprint property, the order in which the map's imports are being verified when loading can cause the editor to crash. For example, trying to load an instanced blueprint for which the package hasn't been loaded yet.

Workaround:
Opening the instance blueprint before changing levels prevents the crash.

Steps to Reproduce

Open UE4 Editor (Third Person Template)
Add 2 C++ classes based on Object & ActorComponent (MyObject & MyActorComp)
In MyObject.h add Blueprintable, EditInlineNew, DefaultToInstanced, Abstract to UCLASS specifier
In MyActorComp.h add the following
- #include "MyObject.h"
- Blueprintable to UCLASS specifier
- ```
UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = test)
		UMyObject* TestObj;
```
Compile
In the editor, create two blueprints based on MyObject (AMyObjectBP & ZMyObjectBP)
Open ThirdPersonCharacter blueprint and add instance of MyActorComp
Set TestObj to AMyObjectBP
Create new level and add instance of ThirdPersonCharacter blueprint
Save new level (SecondLevel) and return to first level
Open ThirdPersonCharacter blueprint and change TestObj from AMyObjectBP to ZMyObjectBP
Close / reopen the editor
Open SecondLevel

Result:
Editor crashes attempting to open the second level

Expected:
Editor switches to the new level for editing

Callstack

LoginId:7156c35640f86204e61b8383f45dee17
EpicAccountId:e8c7fa630b6440f69a25a2c64d6c482c

Fatal error: [File:D:\Build\++UE4+Release-4.15+Compile\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\LinkerLoad.cpp] [Line: 2442] 
Failed import: ATest_C ATest_C /Game/ThirdPersonCPP/Blueprints/ThirdPersonCharacter.ThirdPersonCharacter_C:MyActor_GEN_VARIABLE.ATest_C_0 (file ../../../../../Projects/UnrealProjects/InstancedBPCrash/Content/ThirdPersonCPP/Blueprints/ThirdPersonCharacter.uasset)


UE4Editor_Core!FDebug::AssertFailed() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:349]
UE4Editor_CoreUObject!FLinkerLoad::VerifyImport() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:2442]
UE4Editor_CoreUObject!FLinkerLoad::Verify() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:2118]
UE4Editor_CoreUObject!FLinkerLoad::FinalizeCreation() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:2008]
UE4Editor_CoreUObject!FLinkerLoad::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:716]
UE4Editor_CoreUObject!FLinkerLoad::CreateLinker() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\linkerload.cpp:422]
UE4Editor_CoreUObject!GetPackageLinker() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\linker.cpp:671]
UE4Editor_CoreUObject!LoadPackageInternalInner() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:1233]
UE4Editor_CoreUObject!LoadPackage() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:1477]
UE4Editor_CoreUObject!ResolveName() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:756]
UE4Editor_CoreUObject!StaticLoadObjectInternal() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:843]
UE4Editor_CoreUObject!StaticLoadObject() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectglobals.cpp:903]
UE4Editor_ContentBrowser!FAssetData::GetAsset() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\assetregistry\public\assetdata.h:232]
UE4Editor_ContentBrowser!SContentBrowser::OnAssetsActivated() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:1848]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,TTypeWrapper<void> __cdecl(TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type)>::Execute() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:327]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,void __cdecl(TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type)>::ExecuteIfSafe() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:434]
UE4Editor_ContentBrowser!TBaseDelegate<void,TArray<FAssetData,FDefaultAllocator> const & __ptr64,enum EAssetTypeActivationMethod::Type>::ExecuteIfBound() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:624]
UE4Editor_ContentBrowser!SAssetView::OnListMouseButtonDoubleClick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\contentbrowser\private\sassetview.cpp:3693]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,TTypeWrapper<void> __cdecl(TSharedPtr<FAssetViewItem,0>)>::Execute() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:327]
UE4Editor_ContentBrowser!TBaseSPMethodDelegateInstance<0,SAssetView,0,void __cdecl(TSharedPtr<FAssetViewItem,0>)>::ExecuteIfSafe() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:434]
UE4Editor_ContentBrowser!TBaseDelegate<void,TSharedPtr<FAssetViewItem,0> >::ExecuteIfBound() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:624]
UE4Editor_ContentBrowser!SListView<TSharedPtr<FAssetViewItem,0> >::Private_OnItemDoubleClicked() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\public\widgets\views\slistview.h:800]
UE4Editor_ContentBrowser!STableRow<TSharedPtr<FAssetViewItem,0> >::OnMouseButtonDoubleClick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\public\widgets\views\stablerow.h:287]
UE4Editor_Slate!<lambda_eeb33fd1b480e3cad58a1531d90d2e14>::operator()() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5473]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_eeb33fd1b480e3cad58a1531d90d2e14> >() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:238]
UE4Editor_Slate!FSlateApplication::RoutePointerDoubleClickEvent() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5471]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonDoubleClickEvent() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5454]
UE4Editor_Slate!FSlateApplication::OnMouseDoubleClick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:5432]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:1702]
UE4Editor_Core!FWindowsApplication::DeferMessage() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:2120]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:867]
UE4Editor_Core!FWindowsApplication::AppWndProc() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\windows\windowsapplication.cpp:714]
user32
user32
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:980]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:2977]
UE4Editor!GuardedMain() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
UE4Editor!WinMain() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
kernel32
ntdll

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Cannot Reproduce

Component	UE - Gameplay - Blueprint
Affects Versions	4.14.3, 4.15, 4.16
Target Fix	4.17

Created	Feb 20, 2017
Resolved	Jun 30, 2017
Updated	Apr 27, 2018

UE-42158

Editor crash opening level with instance blueprint component

Editor crash opening level with instance blueprint component

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