Generic ECS Component/System Generating Wrong Queries

Unity Engine
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1

Hi all,

I’ve found what looks to be a bug in Unity ECS ISystem source generation when using generic components in an idiomatic foreach.

using MyNamespace;
using Unity.Burst;
using Unity.Entities;
using UnityEngine;

[assembly: RegisterGenericComponentType(typeof(MyGenericComponent<Foo>))]
[assembly: RegisterGenericSystemType(typeof(MyGenericSystem<Foo>))]

namespace MyNamespace
{
    public struct Foo
    {
        public float Bar;
    }
    
    public struct MyGenericComponent<T> : IComponentData
    {
        public T Value;
    }
    
    public partial struct MyGenericSystem<T> : ISystem
    {
        [BurstCompile]
        public void OnCreate(ref SystemState state)
        {
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            foreach (var component in SystemAPI.Query<MyGenericComponent<T>>())
            {
                Debug.Log($"Hello: {component.Value}");
            }
        }

        [BurstCompile]
        public void OnDestroy(ref SystemState state)
        {
        }
    }
}

With this generic component + system code, it generates this __AssignQueries method in the generated system code:

void __AssignQueries(ref global::Unity.Entities.SystemState state)
{
    var entityQueryBuilder = new global::Unity.Entities.EntityQueryBuilder(global::Unity.Collections.Allocator.Temp);
    __query_2064639144_0 = 
        entityQueryBuilder
            .WithAll<T>()
            .Build(ref state);
    entityQueryBuilder.Reset();
    entityQueryBuilder.Dispose();
}

At runtime, OnCreate, it throws ArgumentException: Unknown Type:MyNamespace.Foo All ComponentType must be known at compile time. For generic components, each concrete type must be registered with [RegisterGenericComponentType]. which makes sense because the source generated code is .WithAll<T> which is wrong. It should be .WithAll<MyGenericComponent<T>>.

Is this a bug in the Unity source generators or am I doing something wrong?