To reproduce:
1. Open attached Unity project "test_unity3d.7z"
2. Open "scene" scene
3. Open "script.cs" in visual studio
4. Make a breakpoint at void Start() (line 12)
5. Click Attach to Unity to start debugging
6. Go into Play mode

Result: Unity Editor has stopped working... (see attached gif "stoppedworking.gif")

Note: you can write whatever code into the start function, it will always crash, so it is not fun() function inside start that is faulty

Reproduced on: 5.6.4p1, 2017.1.2p2, 2017.2.0f3, 2017.3.0b6