RLS build -> Cargo run -> RLS build produces errors

[hcphoenix]

Hello! I'm new to Rust so my ability to minimally reproduce this error is limited and it's hard for me to tell whether this isn't an upstream issue with RLS (I'm unsure how I should interpret the results of rls --cli in order to test). Tested on OSX with v0.4.4 and this 'Getting Started' project for Piston.

Steps to reproduce:

1. Let RLS build the project. You can make changes to trigger rebuilds and they will behave as expected.
2. Run cargo run from the command line.
3. Make any minimal changes to the project to trigger a rebuild from RLS.

Result: VSCode will report the problem [rustc] can't find crate for `serde_derive` which `piston` depends on can't find crate. You can cut out this crate import and others will produce similar crate dependency errors for different dependencies. I can produce this error in other projects but the crate errors vary.

Restarting the IDE "fixes" this issue but RLS will build from scratch instead of incrementally, which makes me suspect that there are fingerprinting issues between RLS and Cargo...

Result of rls --version: rls-preview 0.126.0-stable (f5a0c91 2018-03-26)

Result of cargo --version: cargo 1.26.0 (0e7c5a931 2018-04-06)

[hcphoenix]

Looks like this is a dupe of upstream rust-lang/rls#866, switching to nightly fixes it. Closing.