After installing rust-analyzer in VSC on Windows it didn't work: "Cannot activate rust-analyzer extension: bootstrap error". In my case problem was in AVG antivirus.
Solution: open AVG and add path to the file rust-analyzer.exe (C:\Users[UserName].vscode\extensions\rust-lang.rust-analyzer-0.3.1983-win32-x64\server) to the list of ignored paths (where [UserName] is your user name).
It solved issue in my case.
(I opened new topic, because another one was frozen...)