Rust 1.67 lifetime error; compiles with 1.66 -- what changed?

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Rust 1.66 compiles the citeproc-rs package (GitHub - zotero/citeproc-rs: CSL processor in Rust.) without complaint.

Rust 1.67 fails with a lifetime error:

$ rustup run 1.67 cargo build
...
   Compiling citeproc-io v0.1.0 (/private/tmp/citeproc-rs/crates/io)
error: `QuoteSplitter<'_, impl Iterator<Item = (usize, char)> + '_>::events::{opaque#0}<'_>` does not live long enough
   --> crates/io/src/output/parse_quotes.rs:419:47
    |
419 |                 | MicroNode::Formatted(..) => EachSplitter::Index(Some(ix)),
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: `QuoteSplitter<'_, impl Iterator<Item = (usize, char)> + '_>::events::{opaque#0}<'_>` does not live long enough
   --> crates/io/src/output/parse_quotes.rs:430:21
    |
430 | /                     EachSplitter::Splitter {
431 | |                         index: ix,
432 | |                         splitter,
433 | |                         seen_any: Some(false),
434 | |                     }
    | |_____________________^

error: could not compile `citeproc-io` due to 2 previous errors

I don't see anything in the Changelog / Release Notes (https://github.com/rust-lang/rust/blob/master/RELEASES.md) for 1.67 that could explain this. However, the likely offending soundness change: Neither require nor imply lifetime bounds on opaque type for well formedness by oli-obk · Pull Request #95474 · rust-lang/rust · GitHub says it merged in 1.66, the rustc version which builds just fine. What gives?

Thanks in advance

2

Regression 1.67 "some_fn::{opaque#0}<'_> does not live long enough" · Issue #107426 seems like the same thing; it also reports working on 1.66 and not on 1.67, and was bisected to PR#95474. I can't speak to why the commit says it's present in 1.66 despite being found by the bisection between 1.66 and 1.67.

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If im not mistaken, the merge date checks out for inclusion in 1.66 though?

4

I guess since we identified the breaking change, this has turned into a question about the discrepancy in the merge date and Changelog, versus empirical compliation data. I wondered if there was something about release engineering I did not understand.

5

So, regarding that issue, reproducing it on my laptop shows it regressed in 1.66. Both 1.66.1 and 1.66.0 don’t compile, 1.65 does compile.

On the other hand, for citeproc-rs I can confirm that it breaks in 1.67. So a separate bisection is needed, AFAICT.

So my bisection points to “Support using Self or projections inside an RPIT/async fn #103491”. Which doesn’t look like a PR that’s supposed to break anything?

So I’ve opened a new rustc issue :slight_smile:

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