"Can't find crate" syntax

[raphaelcohn]

Hi, I just followed the instructions at https://serde.rs/codegen-nightly.html for my first experience of Serde. Whilst building the serde_codegen dependency, cargo barfs with :-

   Compiling serde_codegen_internals v0.10.0
     Running `rustc /Users/raph/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_codegen_internals-0.10.0/src/lib.rs --crate-name serde_codegen_internals --crate-type lib -g -C metadata=7453e4105b65d936 -C extra-filename=-7453e4105b65d936 --out-dir /Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps --emit=dep-info,link --target x86_64-unknown-linux-musl -C ar=x86_64-linux-musl-ar -C linker=x86_64-linux-musl-cc -L dependency=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps --extern syn=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libsyn-acd6f0256d61d97a.rlib --cap-lints allow -Anon-snake-case -Anon-upper-case-globals -Wtrivial-casts -Wunused-extern-crates -Wunused-import-braces -Wmissing-copy-implementations -Wmissing-debug-implementations -Ddrop_with_repr_extern`
warning: lint drop_with_repr_extern has been removed: drop flags have been removed
  |
  = note: requested on the command line with `-D drop_with_repr_extern`

   Compiling serde_codegen v0.8.14
     Running `rustc /Users/raph/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_codegen-0.8.14/src/lib.rs --crate-name serde_codegen --crate-type lib -g --cfg feature=\"with-syn\" -C metadata=1c2640c6d5d4a61d -C extra-filename=-1c2640c6d5d4a61d --out-dir /Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps --emit=dep-info,link --target x86_64-unknown-linux-musl -C ar=x86_64-linux-musl-ar -C linker=x86_64-linux-musl-cc -L dependency=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps --extern serde_codegen_internals=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libserde_codegen_internals-7453e4105b65d936.rlib --extern quote=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libquote-90e47f572f455756.rlib --extern syn=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libsyn-acd6f0256d61d97a.rlib --cap-lints allow -Anon-snake-case -Anon-upper-case-globals -Wtrivial-casts -Wunused-extern-crates -Wunused-import-braces -Wmissing-copy-implementations -Wmissing-debug-implementations -Ddrop_with_repr_extern`
warning: lint drop_with_repr_extern has been removed: drop flags have been removed
  |
  = note: requested on the command line with `-D drop_with_repr_extern`

error[E0463]: can't find crate for `syntax`
  --> /Users/raph/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_codegen-0.8.14/src/lib.rs:21:1
   |
21 | extern crate syntax;
   | ^^^^^^^^^^^^^^^^^^^^ can't find crate

error: aborting due to previous error

Build failed, waiting for other jobs to finish...
error: Could not compile `serde_codegen`.

Caused by:
  Process didn't exit successfully: `rustc /Users/raph/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_codegen-0.8.14/src/lib.rs --crate-name serde_codegen --crate-type lib -g --cfg feature="with-syn" -C metadata=1c2640c6d5d4a61d -C extra-filename=-1c2640c6d5d4a61d --out-dir /Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps --emit=dep-info,link --target x86_64-unknown-linux-musl -C ar=x86_64-linux-musl-ar -C linker=x86_64-linux-musl-cc -L dependency=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps --extern serde_codegen_internals=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libserde_codegen_internals-7453e4105b65d936.rlib --extern quote=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libquote-90e47f572f455756.rlib --extern syn=/Volumes/Source/GitHub/lemonrock/dpdk/.cargo/target/x86_64-unknown-linux-musl/debug/deps/libsyn-acd6f0256d61d97a.rlib --cap-lints allow -Anon-snake-case -Anon-upper-case-globals -Wtrivial-casts -Wunused-extern-crates -Wunused-import-braces -Wmissing-copy-implementations -Wmissing-debug-implementations -Ddrop_with_repr_extern` (exit code: 101)

I'm using nightly. Any ideas? It's left me stumped.

[dtolnay]

I have never seen that before but it looks like your compiler and/or cargo may be very old. You should be seeing the following versions or later:

$ rustc --version
  rustc 1.14.0-nightly (16eeeac78 2016-10-18)
$ cargo --version
  cargo 0.13.0-nightly (02fed69 2016-10-18)

If you are using the nightly-only features, you need to use a nightly compiler i.e. update your compiler every night. In general we only ever support the most recent nightly.

[raphaelcohn]

Ah! This particular crate is pinned on a specific nightly compiler because of rust-lang/rust#36954

[dtolnay]

It looks like more of a cargo issue. See whether you can update cargo without updating rustc. I don't know how to do that exactly but #rust IRC might.

Failing that, the other approach will work even on nightly.