Steps to reproduce:
1. Open User-attached project ("RefReturnCrash.zip")
2. Open Scene "Crash"
3. Open Script "Test" and attach the debugger to Unity
4. Create a breakpoint right below the 'Update()' function
5. Play the Scene in Unity
6. Inside VS go to the next step until you reach the 'var write' line
7. Inspect the line by hovering over it and pressing the 'expand' button

Expected: Unity does not crash
Actual: Unity crashes

Reproduced in: 2017.4.10f1, 2018.1.9f2, 2018.2.7f1, 2018.3.0a11

Note: the logs don't seem to provide any useful info or even indicate that the crash happened