The Unity Editor fails to find scripts in assembly definitions when they are laid out in a particular structure

Unity: Scripting

2023.3.X

2023.2.X

2023.1.X

2022.2.X

2021.3.X

2020.3.X

This has been fixed for 2022.3 and onwards, backporting the issues to 2021.3 would involve too much risk for possible breaking changes.

How to reproduce:
1. Open the attached project “compilation-error.zip”
2. Open Scene “SampleScene“ (Assets/Scenes)
3. Enter Play Mode

Expected result: The script is compiled
Actual result: “The referenced script (Unknown) on this Behaviour is missing!” warning in the Console

Reproducible with: 2020.3.43f1, 2021.3.16f1, 2022.2.2f1, 2023.1.0a25

Reproduced on: macOS 13.0.1 (Intel)