Steps to reproduce:
1. Open User-supplied project ("2019.3_First.zip")
2. Open Script "NewBehaviourScript" (Assets window)
3. Comment out "[SerializeReference] IFoo re;"
4. Come back to Unity, let it compile.
5. Go back to script and delete the comment.
6. Go back to Unity.

Reproduced in: 2019.3.0a2, 2019.3.0a3
Not reproduced in: 2019.3.0a1*

Note:
*Can't access 'SerializeReference' due to the protection level
SerializeRefernce appears on 2019.3 alpha