1. Install Rust MSI.
2. "rust-client.disableRustup": true
3. "rust-client.rlsPath": "C:\\Program Files\\Rust stable MSVC 1.38\\bin\\rls.exe"
4. Notice that rust language server errors on startup with

   'C:\Program\' is not recognized as an internal or external command, operable program or batch file.
   

I tried escaping the spaces, but that did not resolve the issue. I also tried wrapping the string in single quotes inside the double quotes, but that resulted in a different error.

For other extensions, "C:\Program Files\path to\file name.extension" works, this problem appears to be specific to this extension.