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Build errors with edition=2018 after clean cargo fix --edition #55592
Description
With nightly-2018-11-01 in Servo, after finally getting cargo fix --edition to complete without warnings. (Which was not easy: rust-lang/rustfix#149, https://github.com/rust-lang-nursery/rustfix/issues/150), I added edition = "2018" to (almost) all Cargo.toml files.
At this point, the theory is that cargo check should Just Work, but it doesn’t. I’ve hit multiple issues, let me know if they should be filed separately.
Dependencies not known to Cargo
error[E0658]: use of extern prelude names introduced with `extern crate` items is unstable (see issue #54658)
--> components/dom_struct/lib.rs:11:5
|
11 | use proc_macro::TokenStream;
| ^^^^^^^^^^
|
= help: add #![feature(extern_crate_item_prelude)] to the crate attributes to enable The "extern prelude" is one way to fix this, but another is to is a crate-local path crate::proc_macro::TokenStream to the name that is introduced by extern crate.
This feature is also missing a tracking issue, the error message points to the implementation PR: #54658 (comment)
Ambiguous imports
error: `time` import is ambiguous
--> components/compositing/compositor.rs:41:5
|
23 | use profile_traits::time::{self, ProfilerCategory, profile};
| ---- may refer to `self::time` in the future
...
41 | use time::{now, precise_time_ns, precise_time_s};
| ^^^^ can refer to external crate `::time`
|
= help: write `::time` or `self::time` explicitly instead
= note: in the future, `#![feature(uniform_paths)]` may become the default
error: aborting due to previous error Migrating generated code
cargo fix did fix similar cases in "normal" source files, but generated code needs to be fixed in the code generator.
These were the remaining ones after I’d already taken care of the absolute paths.
error: expected expression, found reserved keyword `try`
--> /home/simon/servo2/target/debug/build/script-b336041ffdaa5d29/out/Bindings/AnalyserNodeBinding.rs:291:23
|
291 | match try!(crate::dom::bindings::codegen::Bindings::AudioNodeBinding::AudioNodeOptions::new(cx, val)) {
| ^^^ expected expression
error: expected pattern, found reserved keyword `async`
--> /home/simon/servo2/target/debug/build/script-b336041ffdaa5d29/out/Bindings/XMLHttpRequestBinding.rs:1766:57
|
1766 | fn Open_(&self, method: ByteString, url: USVString, async: bool, username: Option<USVString>, password: Option<USVString>) -> Fallible<()>;
| ^^^^^ expected pattern
error: aborting due to previous error New warnings
Not as much of an issue than build errors, but slightly unexpected: switching editions uncovered new unused_mut warnings that were not present before. Maybe this is because 2018 currently implies NLL / MIR-borrowck?
Activity
SimonSapin commentedon Nov 1, 2018
Incorrect warnings
Making the suggested removal causes build errors.
Update collector.rs: Fixes Issue #55599
Enselic commentedon Nov 12, 2024
Triage: To make progress I think we're going to need some (reasonably easy) way to reproduce the issues.
workingjubilee commentedon Jun 19, 2025
My understanding is that Servo from that time can no longer can be built and pass tests with a current rustc because of dependence on unstable compiler features. I am going to close this as "needs repro" will be indefinite from the POV of having something that repros on a current compiler. We can reopen if we find that to be incorrect later.