As a beginner, I'm trying to set up my environment. I found IntelliJ alone shows up the auto-complete for "string".chars() and [""].join() while emacs, vim, and VS Code(RLS and racer) don't. Could you kindly let me know why this is happening if you have any idea?
Yep, @ThomasdenH is correct. Currently, there are two and a half backends for doing IDE stuff for Rust.
IntelliJ, which has a rust compiler frontend written in Kotlin
Racer, a heuristics based lightweight code-completion tool
RLS, which is the official tool, which uses both the compiler and Racer underneath. In particular, Racer is used for code completion, b/c compiler backend is not capable of that
Thus, all editors except IntelliJ use Racer for completion.