How to reproduce:
1. Open the attached project "Assembly Definition Unity Bug Project.zip"
2. Open Assets/NoAutocomplete.cs
Expected results: "using UnityEngine" is not greyed out and "MonoBehaviour" is not white
Actual results: "using UnityEngine" is greyed out and "MonoBehaviour" is white
Reproducible with: 2021.3.45f1, 2022.3.51f1, 6000.0.24f1, 6000.1.0a1
Reproducible on: Windows 10 22H2
Not reproducible on: No other environment tested