varlink_derive compilation error: proc_macro only usable with crates of the proc-macro crate type

[curiousleo]

Hi! I'm trying to use varlink_derive and I'm seeing this compilation error in our CI:

Building src/lib.rs (varlink_derive)

Running rustc --crate-name varlink_derive src/lib.rs --crate-type lib -C opt-level=3 -C codegen-units=2 --edition 2018 -C metadata=6ab36ceda7 -C extra-filename=-6ab36ceda7 --out-dir target/lib --emit=dep-info,link -L dependency=target/deps --extern varlink_generator=/nix/store/fx04h2n6q0ipli7hm7zknspgjfi0qiva-rust_varlink_generator-8.0.0/lib/libvarlink_generator-10e2cd43da.rlib --cap-lints allow --color always

error: the `#[proc_macro]` attribute is only usable with crates of the `proc-macro` crate type

  --> src/lib.rs:61:1

   |

61 | #[proc_macro]

   | ^^^^^^^^^^^^^

error: the `#[proc_macro]` attribute is only usable with crates of the `proc-macro` crate type

  --> src/lib.rs:84:1

   |

84 | #[proc_macro]

   | ^^^^^^^^^^^^^

error: aborting due to 2 previous errors

(from https://travis-ci.org/target/lorri/jobs/623110880#L2842-L2856)

I noticed two things:

• varlink_derive is indeed a lib: https://github.com/varlink/rust/blob/831604826923929c0a1212309570a77a61d1996c/varlink_derive/Cargo.toml#L12
• varlink_derive has proc_macro = true: https://github.com/varlink/rust/blob/831604826923929c0a1212309570a77a61d1996c/varlink_derive/Cargo.toml#L13 whereas the Rust docs say that such libraries should set proc-macro = true (note the dash).

I don't get this compilation error in all build environments though - any idea what could be going on here?

[curiousleo]

Hm, just judging by the uses of proc_macro = true (3680 on Github) and proc-macro = true (3926 on Github) it seems that they're both equally valid.

[curiousleo]

The issue here appears to be with Carnix: https://nest.pijul.com/pmeunier/carnix/discussions/41. Closing this ticket.