Reproduction steps:
1. Open the attached project "dll_bug.zip"
2. In Assets open script_example.cs script
3. Notice that there are no reference errors for the ConcurrentDictionary object
4. Add the attached System.Collections.Concurrent.dll to Assets
3. Click on the DLL file and disable all checkboxes in the Inspector
4. Open script_example.cs script again
Expected result: No reference error for the ConcurrentDictionary object is shown
Actual result: Duplicate reference error for ConcurrentDictionary object is shown even though the DLL file was unloaded and disabled for all platforms including Editor
Reproducible with: 2.0.12 (2019.4.37f1), 2.0.14 (2019.4.37f1, 2020.3.31f1, 2021.2.16f1, 2022.1.0b12, 2022.2.0a9)
Notes:
- Restarting the Unity or reimporting the script does not fix the error
- Does not reproduce with JetBrains Rider IDE