Visual Studio builds currently fail when a project includes a UFUNCTION with Server, Reliable, and WithValidation specifiers (with appropriate definitions in the source file).

Using UFUNCTION(Server, Reliable, WithValidation) with an RPC function results in a failed build in Visual Studio.

The same test in Main yields a different set of error messages.

1. Create a new code project using the First Person template, no starter content.
2. In the .h file for the project, add a #include "Engine.h" line.
3. In the .h file for the character class, add the following code under a public: access specifier:

   UFUNCTION(Server, Reliable, WithValidation)
   void ServerTestMessage();
   

4. In the .cpp file for the project's character class, add the following code, filling in the class name as needed:

   void /*ClassName*/::ServerTestMessage()
   {
   	if (Role < ROLE_Authority)
   	{
   		if (GEngine)
   		{
   			GEngine->AddOnScreenDebugMessage(-1, 5.f, FColor::Green, TEXT("Greetings from the ServerTestMessage function."));
   		}
   		ServerTestMessage();
   	}
   }
   
   bool /*ClassName*/::ServerTestMessage_Validate()
   {
   	return true;
   }
   
   void /*ClassName*/::ServerTestMessage_Implementation()
   {
   	ServerTestMessage();
   }
   

5. Add the line bReplicates = true; to the constructor for the character class.
6. Build the project in Visual Studio.

RESULT:
The build fails with the following errors:

1>TestMulticast2.generated.cpp.obj : error LNK2005: "public: void __cdecl ATestMulticast2Character::ServerTestMessage(void)" (?ServerTestMessage@ATestMulticast2Character@@QEAAXXZ) already defined in TestMulticast2Character.cpp.obj
1>C:\Users\Tim.Lincoln\Documents\Unreal Projects\TestMulticast2\Binaries\Win64\UE4Editor-TestMulticast2.dll : fatal error LNK1169: one or more multiply defined symbols found

EXPECTED:
The build completes successfully.