Migrate LSP server for Rust: rls to rust-analyzer

[t-sin]

STATUS: now testing

I saw some delay in using it, so I think it's needed to more testing. So don't merge this PR now.

[rdaum]

Is there any update on this? I keep looking at lem but not switching to it because of lack of good support for Rust LSP development flow.

I don't know enough about lem's internals to know if I could just cherry-pick this in?

[rafaelsamenezes]

Is there any update on this? I keep looking at lem but not switching to it because of lack of good support for Rust LSP development flow.

I don't know enough about lem's internals to know if I could just cherry-pick this in?

You can get the same results of this PR with your init file ($HOME/.config/lem/init.lisp). Just add:

(lem-lsp-mode/lsp-mode::define-language-spec
    (rust-spec lem-rust-mode:rust-mode)
  :language-id "rust"
  :root-uri-patterns '("Cargo.toml")
  :command '("rust-analyzer")
  :install-command "rustup component add rust-analyzer"
  :readme-url "https://github.com/rust-lang/rust-analyzer"
  :connection-mode :stdio)

More info at: https://lem-project.github.io/usage/LSP/