[Project Model] Error when loading a Cargo.toml with edition

[kngwyu]

When the Cargo.toml in workspace-root contains edition, ProjectModelProvider causes an error
like

ERROR 2018-09-06T05:58:45Z: rls::actions: failed to fetch project model, using fallback: failed to parse manifest at `/home/yu/Programs/lark/Cargo.toml`
ErrorMessage { msg: "the cargo feature `edition` requires a nightly version of Cargo, but this is the `dev` channel" }

and can't do completion for external crates.
According to @matklad , it's related to https://github.com/rust-lang/cargo/blob/b15ee255e5cf625f15ff3f5ecdc6efb76e402768/src/cargo/lib.rs#L231

[Xanewok]

As @dwijnand pointed out, the edition should be stabilised soon: rust-lang/cargo#5984

However, I'm puzzled by the cargo feature `edition` requires a nightly version of Cargo, but this is the `dev` channel. Shouldn't dev channel be an 'all bets are off' thing and if that's a manually built bleeding edge Cargo, then nightly features should obviously be permitted? I know Rustfmt does this.

[dwijnand]

Good link! Turns out that change in Rustfmt is very recent: https://github.com/rust-lang-nursery/rustfmt/pull/2948/files

So perhaps RLS just needs the same change?

[Xanewok]

@kngwyu can we close this? The edition is stable now and shouldn't pose any more problems.

[kngwyu]

Yeah, I just forgot to close this

[dwijnand]

Thanks!