Unity3D - Missing .sln project file?

Question

C++ / C#

After updating Unity to 2018, the .sln project file was missing from the folder.
Now, when opening scripts, it does not see dependencies and auto-completion and highlighting do not work.
Googled, but found only in one place:
unity3d.ru/distribution/viewtopic.php?f=105&t=35139
he does not provide a solution.
Does anyone know how to restore this file?

Answer 1

Solution found!!!!
It turns out this is a known issue:
https://forum.unity.com/threads/visual-studio-wont...
https://forum.unity.com/threads/solved-unity-2018-...
and a bunch of requests to the Unity support
I was helped by updating VS 2017 through its built-in installer.
Thanks to all))))