Compile with stable Rust

[SergioBenitez]

The following features need to be stabilized before Rocket can compile on stable:

• proc_macro_hygiene (Tracking issue for procedural macros and "hygiene 2.0" rust-lang/rust#54727)
• associated_consts (Tracking issue for associated_consts feature rust-lang/rust#29646)
• conservative_impl_trait (Tracking issue for impl Trait (RFC 1522, RFC 1951, RFC 2071) rust-lang/rust#34511)
• drop_types_in_const (permit Drop types in constants (tracking issue for RFC #1440) rust-lang/rust#33156)
• more_io_inner_methods (Tracking issue for 'more_io_inner_methods' rust-lang/rust#41519)
• pub_restricted (Tracking issue for pub(restricted) privacy (RFC #1422) rust-lang/rust#32409)
• struct_field_attributes (Tracking issue for struct_field_attributes rust-lang/rust#41681)
• use_extern_macros (Tracking issue for "macro naming and modularisation" (RFC #1561) rust-lang/rust#35896)
• fn_box (Tracking issue for FnBox() rust-lang/rust#28796)
• try_from (Tracking issue for TryFrom/TryInto traits rust-lang/rust#33417)

The following dependencies rely on nightly features and must be updated before Rocket can compile on stable:

• pear (SergioBenitez/Pear@333c9bf)

Update (Feb 07, 2017): Added list of features used by Rocket.
Update (Feb 28, 2017): Added lookup_host feature.
Update (Mar 21, 2017): pub_restricted was stabilized!
Update (Mar 30, 2017): Added never_type feature.
Update (Apr 16, 2017): Added concat_idents feature.
Update (May 19, 2017): Added struct_field_attributes and more_io_inner_methods features.
Update (May 19, 2017): concat_idents is no longer used.
Update (May 19, 2017): Added links to tracking issues.
Update (May 20, 2017): type_ascription is no longer used.
Update (Jun 19, 2017): struct_field_attributes was stabilized!
Update (Jun 24, 2017): Added try_trait feature.
Update (Jul 1, 2017): more_io_inner_methods was stabilized!
Update (Jul 9, 2017): associated_consts was stabilized!
Update (Sep 7, 2017): lookup_host is no longer used.
Update (Sep 14, 2017): drop_types_in_const was stabilized!
Update (Sep 14, 2017): Added decl_macro feature.
Update (Mar 26, 2018): conservative_impl_trait, never_type, and i128_type were stabilized!
Update (Apr 22, 2018): Added fnbox feature.
Update (Apr 26, 2018): never_type stabilization was reverted (rust-lang/rust#50121).
Update (May 5, 2018): Swapped macro_reexport for use_extern_macros.
Update (Jul 29, 2018): Added crate_visibility_modifier and try_from features.
Update (Aug 5, 2018): custom_derive is no longer used.
Update (Aug 17, 2018): use_extern_macros was stabilized!
Update (Sep 3, 2018): const_fn is no longer used.
Update (Sep 26, 2018): Added label_break_value feature.
Update (Oct 9, 2018): Removed compiler plugin features (custom_attribute, plugin).
Update (Oct 9, 2018): Updated proc_macro features.
Update (Mar 9, 2019): try_from was stabilized!
Update (Apr 13, 2019): fnbox is no longer used.
Update (Jul 9, 2019): never_type is no longer used.
Update (Jul 19, 2019): decl_macro is no longer used.
Update (Sep 9, 2019): specialization is no longer used.
Update (Sep 10, 2019): label_break_value is no longer used.
Update (Sep 18, 2019): try_trait is no longer used.
Update (Sep 21, 2019): crate_visibility_modifier is no longer used.
Update (May 19, 2020): proc_macro_hygiene was stabilized!
Update (Jul 16, 2020): proc_macro_diagnostics is no longer used.
Update (Jul 16, 2020): proc_macro_span is no longer used.
Update (Jul 21, 2020): pear was updated to be stable-compatible.

[steveklabnik]

Looks like this primarily depends on rust-lang/rust#38356

(Or syntex)

[rrichardson]

Syntex should get this onto stable much more quickly, since the macros > 1.1 effort seems to be just beginning to congeal.

https://news.ycombinator.com/item?id=13245975

[steveklabnik]

since the macros > 1.1 effort seems to be just beginning to congeal.

This needs more than macros 1.1, it needs 2.0. (If it only needed 1.1, then it could go stable in 1.15)

[rrichardson]

I intended > 1.1 to indicate "after 1.1" but that wasn't very clear.
I've seen the procedural macros effect referenced as 1.2 as well as 2.0. 2.0 does make more sense, since it is a much broader scope, as I understand it.

[mgattozzi]

I've started working on getting syntex to work with this until macros are stabilized (which might be a while). I've got time over the holidays from work so I'll post any progress I make!

[SergioBenitez]

Rocket uses much more than just plugins from nightly. The set of features Rocket currently uses are:

#![feature(plugin)]
#![feature(custom_derive)]
#![feature(custom_attribute)]
#![feature(specialization)]
#![feature(conservative_impl_trait)]
#![feature(drop_types_in_const)]
#![feature(associated_consts)]
#![feature(const_fn)]

These uses are important and contribute to the pithiness of the API, so they will stick around until they're stabilized. Until then, I don't believe Rocket will run on stable.

With that being said, I believe that the ergonomics of syntex are very poor, and I don't want to recommend a subpar solution to users. I'm all for getting Rocket to work on stable as soon as possible, but I'm not willing to compromise ergonomics and usability to make that happen.

[beefsack]

I'm all for getting Rocket to work on stable as soon as possible, but I'm not willing to compromise ergonomics and usability to make that happen.

I'd love to see it go stable as soon as possible, but I feel you've got the right values for the project. Accessibility is arguably more important for web frameworks than it is for other frameworks and libraries.

[mgattozzi]

Just from trying to get it to work with syntex it's hard. I might try some more this week but you're right. It might just be worth it to wait till those features stabilize.