Unity cannot compile when extending NetworkBehaviour in Generics

[JohnnyRacket]

Description

After refactoring code to have generic base types, Unity refused to compile until all generics with types extending NetworkBehaviour were swapped to MonoBehaviour

Reproduce Steps

1. Create a generic that extends NetworkBehaviour, such as: public abstract class BaseActionController<ActionType,CharacterType> : NetworkBehaviour where ActionType : BaseAction<CharacterType> where CharacterType : NetworkBehaviour

2. Try to compile and run project.

Actual Outcome

Unity.Netcode.Editor.CodeGen.NetworkBehaviourILPP: (0,0): error - System.NullReferenceException: Object reference not set to an instance of an object

Expected Outcome

Code compiles.

Environment

• OS: Windows 11
• Unity Version: 2023.1.0b20
• Netcode Version: 1.5.1
• Netcode Commit: 7a969f8

Additional Context

For now I have managed to replace the code with extending MonoBehaviour and it compiles, but it does not seem like an ideal limitation as I may have to assert types down the road.

[fluong6]

@JohnnyRacket We have a few bug fixes for this issue in NGO 1.5.2. Can you please upgrade to NGO 1.5.2 and if the issue stills occurs, can you please let us know?

[Reag]

Im on 1.5.2 and it does not appear to be fixed for me

[zachstronaut]

@fluong6 I believe this is the fix incorporated into 1.5.2: https://github.com/Unity-Technologies/com.unity.netcode.gameobjects/pull/2603/files

However, there do remain compilation problems with generic base classes that extend NetworkBehaviour. I've run into them myself. I'll try to find a specific example where this isn't fully fixed yet. In the meantime, though, somebody could take a look at all these related tickets -- some of which are being dismissed as fixed in 1.5.2 when I'm not sure all of them are indeed fixed.

#2690
#2193
#714
#937
#572
#1860
#792

Granted, it sounds like this may not be a bug but instead a feature request: to more thoroughly support generic base classes that extend NetworkBehaviour in Netcode.