add `#![feature(negative_impls)]` but negative_impls doesnt exist localy

[JAicewizard]

Crate name:
rustt
Build failure link:
https://docs.rs/crate/rustt/0.1.1/builds/235564

Additional details:
The logs say I should use #![feature(negative_impls)] but 1: I cant find any information about this issue, and most importantly 2: locally using nightly 2020-03-18 I cant build myself let alone upload to crates.io when adding this crate attribute.

[jyn514]

There is info about negative impls in rust-lang/rust#68318 (there was a link in the long error message).

I'm confused how your crate is building locally without this feature but still having impl !Trait {}. Are you using nightly? Does cargo doc work locally?

[JAicewizard]

yes I am using nightly and it is documenting properly (without #![feature(negative_impls)]).
Adding #![feature(negative_impls)] makes it not doc and throw the error:

error[E0635]: unknown feature `negative_impls`
  --> src/lib.rs:80:12
   |
80 | #![feature(negative_impls)]
   |            ^^^^^^^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0635`.
error: Could not document `rustt`.

Caused by:
  process didn't exit successfully: `rustdoc --edition=2018 --crate-type lib --crate-name rustt src/lib.rs -o /home/jaap/Projects/rustt/target/doc --error-format=json --json=diagnostic-rendered-ansi -L dependency=/home/jaap/Projects/rustt/target/debug/deps --extern integer_encoding=/home/jaap/Projects/rustt/target/debug/deps/libinteger_encoding-9714e9561b194cec.rmeta --extern serde=/home/jaap/Projects/rustt/target/debug/deps/libserde-d23ce8522e605b3c.rmeta` (exit code: 1)

nightly version is rustc 1.44.0-nightly (f509b26a7 2020-03-18) which is the latest according to rustup.

[jyn514]

@JAicewizard I tried building this locally and got the same errors as from the docs.rs build:

error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
  --> src/ttv3/serde/mod.rs:40:6
   |
40 | impl !NotImplementKey for CustomNode {}
   |      ^^^^^^^^^^^^^^^^
   |
   = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
   = help: add `#![feature(negative_impls)]` to the crate attributes to enable

Are you sure you're using 1.44 to document? I got this error with rustdoc 1.47.0-nightly (6e87bacd3 2020-07-31), maybe try updating?

[JAicewizard]

I am very sure that at the time this was in deed the case!!!
currently on 46 nightly and I got the error now, and adding #![feature(negative_impls)] does actually work now.
I guess it was some kind of version difference, I don't know how since I tried updating a couple times (at the time).

[jyn514]

Very strange. Glad you figured it out though :) I see that you published 0.1.2 and it built so I'm going to close this.