Reproduction steps:
1. Open Unity and create new project
2. Create new C# script
3. Open and edit C# script and close it
4. Enable Play mode
5. Open the C# script

Expected: the script should be part of the project and writing MonoBehaviour method name ("update", "awake"...) should autocomplete/suggest code
Actual: the script is part of "Assembly-CSharp" and MonoBehaviour method names are not autocompleted/suggested

Reproduced on: 2018.1.0b1; 2018.1.0b5; 2018.2.0a1
Not reproduced on: 2017.3.1f1; 2018.1.0a7
Regression introduced: 2018.1.0b1

Note: reproduced only with Visual Studio 15.5.4