This is a backend for twoslash that supports annotating Rust code.
For usage information, see js/index.ts. Right now you will
need to install the TypeScript/JavaScript client from this git repo directly.
You will also need the twoslash-rust binary (which is effectively a shell over
rust-analyzer), which you can get via cargo install rust-twoslash --git https://github.com/ayazhafiz/twoslash-rust.git.
Make sure to clone rust-analyzer as a submodule. I couldn't get recent releases of rust-analyzer on crates.io to compile, so we're doing submodules for now.
You're best off developing with --release. Turns out rust-analyzer is really
slow at indexing sysroot in debug builds.