Rust cannot compile itself, as a cargo dependency

[kd8azz]

Cargo.toml:

[dependencies]
syntax = { git = "https://github.com/rust-lang/rust/", branch = "stable" }

Command:
cargo build --all

Expected: Syntax module is imported.
Actual:
Stable and Beta rustc channels complian "#![feature] may not be used ..."
Nightly rustc channel just doesn't work.

[oli-obk]

what's the exact issue on nightly? This is expected not to work on stable/beta

[kd8azz]

Is there a supported way of using libsyntax as a dependency, without using the nightly compiler? I assume the nightly compiler will be broken 3 out of 4 nights.

Here's nightly's error:

$ cargo build --all --verbose
       Fresh serialize v0.0.0 (https://github.com/rust-lang/rust/?branch=stable#f3d6973f)
       Fresh log v0.3.8
       Fresh bitflags v0.8.2
   Compiling rustc_data_structures v0.0.0 (https://github.com/rust-lang/rust/?branch=stable#f3d6973f)
     Running `rustc --crate-name rustc_data_structures /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/f3d6973/src/librustc_data_structures/lib.rs --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=0a44aaf343deb2c8 -C extra-filename=-0a44aaf343deb2c8 --out-dir /home/user/Source/my_project/target/debug/deps -L dependency=/home/user/Source/my_project/target/debug/deps --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-18a6ea8c4c6023d1.so --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-18a6ea8c4c6023d1.rlib --extern log=/home/user/Source/my_project/target/debug/deps/liblog-5fde67c83969596f.rlib --cap-lints allow`
error[E0308]: mismatched types
   --> /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/f3d6973/src/librustc_data_structures/array_vec.rs:149:28
    |
149 |                 array_vec: Shared::new(self as *mut _),
    |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `core::ptr::Shared`, found enum `core::option::Option`
    |
    = note: expected type `core::ptr::Shared<array_vec::ArrayVec<A>>`
               found type `core::option::Option<core::ptr::Shared<_>>`
    = help: here are some functions which might fulfill your needs:
            - .unwrap()

error[E0308]: mismatched types
  --> /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/f3d6973/src/librustc_data_structures/obligation_forest/node_index.rs:22:37
   |
22 |         unsafe { NodeIndex { index: NonZero::new((value as u32) + 1) } }
   |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `core::nonzero::NonZero`, found enum `core::option::Option`
   |
   = note: expected type `core::nonzero::NonZero<_>`
              found type `core::option::Option<core::nonzero::NonZero<_>>`
   = help: here are some functions which might fulfill your needs:
           - .unwrap()

error: aborting due to 2 previous errors

error: Could not compile `rustc_data_structures`.

Caused by:
  process didn't exit successfully: `rustc --crate-name rustc_data_structures /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/f3d6973/src/librustc_data_structures/lib.rs --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=0a44aaf343deb2c8 -C extra-filename=-0a44aaf343deb2c8 --out-dir /home/user/Source/my_project/target/debug/deps -L dependency=/home/user/Source/my_project/target/debug/deps --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-18a6ea8c4c6023d1.so --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-18a6ea8c4c6023d1.rlib --extern log=/home/user/Source/my_project/target/debug/deps/liblog-5fde67c83969596f.rlib --cap-lints allow` (exit code: 101)

[arielb1]

You are trying to compile a stable rustc (see branch=stable) using a nightly rustc. That doesn't work - you should use a nightly rustc instead.

[arielb1]

@kd8azz

Also, the nightly compiler is working most of the time - we have quite good CI. You can also pick a good nightly and pin to it, Servo-style.

[kennytm]

There is no way to use libsyntax on stable yet. This is currently tracked by #41732.

If you just want to parse Rust on stable, use syn.

If you want to use libsyntax on nightly, just write

#![feature(rustc_private)]
extern crate syntax;

You don't need to add any dependency to Cargo.

[kd8azz]

@arielb1 > You are trying to compile a stable rustc (see branch=stable) using a nightly rustc. That doesn't work - you should use a nightly rustc instead.

Ok, I can accept that.

@arielb1 > Also, the nightly compiler is working most of the time

Thanks, that's good to hear. Sorry for doubting your CI process. I just had a long day trying to get started on a project, and this was my problem.

@kennytm Thanks!

I just changed branch="master" and reran. It is currently broken, but I have a path forward now (as it turns out I was doing things the wrong way).

 $ cargo build --all --verbose
    Updating git repository `https://github.com/rust-lang/rust/`
   Compiling serialize v0.0.0 (https://github.com/rust-lang/rust/#a36d93d3)
     Running `rustc --crate-name serialize /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/a36d93d3/src/libserialize/lib.rs --crate-type dylib --crate-type rlib --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=c8d63cf921f261f3 -C extra-filename=-c8d63cf921f261f3 --out-dir /home/user/Source/my_project/target/debug/deps -L dependency=/home/user/Source/my_project/target/debug/deps --cap-lints allow`
       Fresh bitflags v0.8.2
   Compiling syntax v0.0.0 (https://github.com/rust-lang/rust/#a36d93d3)
       Fresh log v0.3.8
     Running `rustc --crate-name build_script_build /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/a36d93d3/src/libsyntax/build.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=f3b37b4175585bbe -C extra-filename=-f3b37b4175585bbe --out-dir /home/user/Source/my_project/target/debug/build/syntax-f3b37b4175585bbe -L dependency=/home/user/Source/my_project/target/debug/deps --cap-lints allow`
     Running `/home/user/Source/my_project/target/debug/build/syntax-f3b37b4175585bbe/build-script-build`
   Compiling rustc_data_structures v0.0.0 (https://github.com/rust-lang/rust/#a36d93d3)
     Running `rustc --crate-name rustc_data_structures /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/a36d93d3/src/librustc_data_structures/lib.rs --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=bb0d1cab5f0c2dc1 -C extra-filename=-bb0d1cab5f0c2dc1 --out-dir /home/user/Source/my_project/target/debug/deps -L dependency=/home/user/Source/my_project/target/debug/deps --extern log=/home/user/Source/my_project/target/debug/deps/liblog-b6e3b66094cb7016.rlib --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-c8d63cf921f261f3.so --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-c8d63cf921f261f3.rlib --cap-lints allow`
error: use of unstable library feature 'discriminant_value': recently added, follows RFC (see issue #24263)
   --> /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/a36d93d3/src/librustc_data_structures/stable_hasher.rs:379:34
    |
379 | impl<T, CTX> HashStable<CTX> for ::std::mem::Discriminant<T> {
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: add #![feature(discriminant_value)] to the crate attributes to enable

error: aborting due to previous error

error: Could not compile `rustc_data_structures`.

Caused by:
  process didn't exit successfully: `rustc --crate-name rustc_data_structures /home/user/.cargo/git/checkouts/rust-dd78c2fc2695b8eb/a36d93d3/src/librustc_data_structures/lib.rs --crate-type dylib --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=bb0d1cab5f0c2dc1 -C extra-filename=-bb0d1cab5f0c2dc1 --out-dir /home/user/Source/my_project/target/debug/deps -L dependency=/home/user/Source/my_project/target/debug/deps --extern log=/home/user/Source/my_project/target/debug/deps/liblog-b6e3b66094cb7016.rlib --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-c8d63cf921f261f3.so --extern serialize=/home/user/Source/my_project/target/debug/deps/libserialize-c8d63cf921f261f3.rlib --cap-lints allow` (exit code: 101)

Thank you everyone for your help.