As of the latest plugin version for Rust, the imports that are unused
are not anymore auto cleaned when pressing Ctrl+Alt+O.
To fix this issue, go to Settings > Editor > Inspections > Rust > Lint.
Uncheck the Enable inspection only if procedural macros are enabled
Add the following VM option if you're experiencing white boxes in the UI. This option is enabled by default on the pre-built versions.
-Dprism.dirtyopts=false