Including steam_api.h causes errors

Development Platform & Builds
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1

I am using version 4.18 and adding Steam DLC checks in a C++ UserWidget child class (named WG_Steam_Menu). I am referencing A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums and when I add the include to the built-in Steam API:

#include "ThirdParty/Steamworks/Steamv139/sdk/public/steam/steam_api.h"

I get syntax errors related to my class which was previously building just fine:

Error C2059 syntax error: ‘,’ MyGame C:.…MyGame\WG_Steam_Menu.gen.cpp 49

Error C2143 syntax error: missing ‘;’ before ‘}’ C:.…MyGame\WG_Steam_Menu.gen.cpp 57

Error C2065 ‘ClassParams’: undeclared identifier C:.…MyGame\WG_Steam_Menu.gen.cpp 58

etc. My files look like:


**MyGame.Build.cs:** 
using UnrealBuildTool;

public class MyGame : ModuleRules
{
	public MyGame(ReadOnlyTargetRules Target) : base(Target)
	{
		PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;
	
		PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "Steamworks" });

		PrivateDependencyModuleNames.AddRange(new string[] {  });

		// Uncomment if you are using Slate UI
		// PrivateDependencyModuleNames.AddRange(new string[] { "Slate", "SlateCore" });
		
		// Uncomment if you are using online features
		PrivateDependencyModuleNames.Add("OnlineSubsystem");

        // To include OnlineSubsystemSteam, add it to the plugins section in your uproject file with the Enabled attribute set to true
        DynamicallyLoadedModuleNames.Add("OnlineSubsystemSteam");
    }
}

**MyGame.uproject:** 
{
	"FileVersion": 3,
	"EngineAssociation": "4.18",
	"Category": "",
	"Description": "",
	"Modules": [
		{
			"Name": "MyGame",
			"Type": "Runtime",
			"LoadingPhase": "Default",
			"AdditionalDependencies": [
				"UMG"
			]
		}
	],
	"Plugins": [
		{
			"Name": "OnlineSubsystemSteam",
			"Enabled": true
		}
	]
}

**WG_Steam_Menu.h:** 
#pragma once

#include "CoreMinimal.h"
#include "Blueprint/UserWidget.h"
#include "ThirdParty/Steamworks/Steamv139/sdk/public/steam/steam_api.h"
#include "WG_Steam_Menu.generated.h"

/**
 * 
 */
UCLASS()
class MYGAME_API UWG_Steam_Menu : public UUserWidget
{
	GENERATED_BODY()
	
};

**WG_Steam_Menu.cpp:** 
#include "WG_Steam_Menu.h"

These errors seem similar to strange errors I've seen in the past related to project file caching so I deleted all temporary files and re-generated the project files. However building the new project still throws the errors above. What is going on?
2

So this was another case of Visual Studio and Unreal getting confused by file changes. After completely deleting the project and re-cloning it from source control it built without errors.