Since this thread is a top result when searching the web for the error message encountered, it might be worth adding to it. Apologies if this post wanders slightly of topic with regards of being unrelated to
Attempting to use rls in a project with both a binary and a library gives the error message of the library being not-existent. While that is documented in the debug instructions for rls, along with how to work around it, I found it rather hard to find. As quoted from page linked above:
You can build the library by setting
true (this is often most useful).
Before finding the above configuration I did follow the suggestion of trying rust-analyzer instead of rls, and attempted to use it for a full day. From my perspective the latter is still a lot more stable, and the former was practically useless to me. I have not dug into any possible cause, but with rls
ALERename in vim-ale works flawlessy. While the same software with rust-analyzer seem to find only a fraction of the symbols, making code navigation unergonomic and leaving code in a non-compiling state after refactoring.
Unfortunately rust-analyser seems to have a bit of stabilizing left before it can replace rls.