rustsym | A tool to query symbols from rust code for use in IDEs

Although there could be many possible causes of a problem with the Rust extension in Visual Studio Code, the following steps should help anyone with issues of this kind:

• Do not use the old extension "Rusty Code", since it's no longer maintained. Instead, you have two options:
  • The official rust-lang.rust extension is developed by an official Rust team and is focused on Rust Language Server (RLS) integration. It is in active development.
  • The kalitaalexey.vscode-rust extension, forked from Rusty Code, is older but possibly more stable than the official extension when run in Legacy Mode. It is currently under very passive maintenance however.
• You might need to build your project so that dependencies are downloaded and compiled locally, thus enabling the extension to retrieve additional information about them. Every time you modify your dependency list, be sure that your program is declaring them with extern crate, then run cargo build on your project. If the Code command is available, press F1 then type in "build" and enter. Don't forget to build after cleaning the project as well.
• It's always worth making sure that the extension is up to date and properly configured. Update the extension, and check out the respective documentation for instructions on how to make it work. when using kalitaalexey.vscode-rust, see the main documentation and have it work in either Legacy mode or using the RLS.
• The RLS has come a long way over the past few years, and should be the default choice for Visual Studio Code. The RLS can even be installed automatically from the IDE, via Rustup.
• Check the status bar. If something is wrong, it should tell you so. Open the extension task's output window for error messages. If something still isn't right, try reloading your window.

If there's still a problem after these steps, it might actually be a bug, which should be reported.