Does not compile with Rust stable channel

[KD0BPV]

We should try to avoid using language features that require unstable builds of the tool-chain.

% cargo build
   Compiling state v0.3.2
   Compiling byteorder v1.1.0
   Compiling smallvec v0.4.4
   Compiling percent-encoding v1.0.1
   Compiling utf8-ranges v1.0.0
   Compiling pear_codegen v0.0.10
   Compiling yaml-rust v0.3.5
   Compiling yansi v0.3.4
error[E0554]: #[feature] may not be used on the stable release channel
 --> /home/mark/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:1:1
  |
1 | #![feature(const_fn)]
  | ^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #[feature] may not be used on the stable release channel
 --> /home/mark/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:2:1
  |
2 | #![feature(const_unsafe_cell_new)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #[feature] may not be used on the stable release channel
 --> /home/mark/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:3:1
  |
3 | #![feature(const_atomic_usize_new)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0554]: #[feature] may not be used on the stable release channel
 --> /home/mark/.cargo/registry/src/github.com-1ecc6299db9ec823/state-0.3.2/src/lib.rs:4:1
  |
4 | #![feature(const_atomic_bool_new)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error(s)

error: Could not compile `state`.
warning: build failed, waiting for other jobs to finish...
error[E0554]: #[feature] may not be used on the stable release channel
 --> /home/mark/.cargo/registry/src/github.com-1ecc6299db9ec823/yansi-0.3.4/src/lib.rs:1:32
  |
1 | #![cfg_attr(feature="nightly", feature(const_atomic_bool_new))]
  |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error(s)

error: Could not compile `yansi`.
warning: build failed, waiting for other jobs to finish...
error[E0554]: #[feature] may not be used on the stable release channel
 --> /home/mark/.cargo/registry/src/github.com-1ecc6299db9ec823/pear_codegen-0.0.10/src/lib.rs:1:1
  |
1 | #![feature(plugin_registrar, rustc_private, quote)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error(s)

error: Could not compile `pear_codegen`.
warning: build failed, waiting for other jobs to finish...
error: build failed
cargo build  5.21s user 0.27s system 195% cpu 2.804 total

[BanjoFox]

Wouldn't that include most of Rocket? >.>

[pwoolcoc]

Yea, the only unstable feature our application code uses outside of rocket.rs-related stuff is try_from, and that is mostly there as a convenience -- we could easily get rid of that.

Here is the tracking issue from rocket.rs about compiling on stable: rwf2/Rocket#19

[KD0BPV]

Does it? Hrm. That's kind of disappointing. Oh well, I'll see if I can get my Gentoo system updated to nightly, then.

[pwoolcoc]

It might be good to use the "version file" feature of rustup.rs to pin us to a specific nightly version -- that way, anyone using rustup.rs to managed their installed toolchains will always get the specific nightly version of the toolchain that we know works.

https://github.com/rust-lang-nursery/rustup.rs#the-toolchain-file

[KD0BPV]

That sounds like a good plan. Now to just get my system to switch to rustup, while still keeping Firefox installed. I can understand Firefox having Rust as a build dependency, but why do I have to keep it as a run-time dependency? This could get tricky...

[BanjoFox]

@KD0BPV
According to the Rocket documentation you should be able to do directory-specific Rust.

If you prefer, once we setup a project directory in the following section, you can use per-directory overrides to use the nightly version only for your Rocket project by running the following command in the directory:
rustup override set nightly