I have been using Visual Studio 2017 for several months on a development machine. This morning it says says setup incomplete. Am I missing something?
VS 2017 (15.6.6) was fine for me on Friday 6/1/18 on Windows 10, but same issue as OP today after a restart.
As suggested by the dialog and Retired Ninja, I ran the Visual Studio Installer (to 15.7.3 after updating VS Installer) and that fixed it.
Note that the 15.7.3 update was a 7.73 GB download. Your download size may vary.