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syn dependency version bound is incompatible with prettyplease #3448
Description
I have the following build dependencies in my crate:
bindgen = "0.73.1"
cmake = "0.1.58"The syn version bound in bindgen (>=2, <4) allows Cargo to select a 2.x release (2.0.119) for bindgen and a 3.x release (3.0.3) for prettyplease, which causes a compilation error. Why cargo picks an old syn release for bindgen is beyond me.
This is one of those cases where I just shut my computer off and go do something else, because it is 11pm and I do not feel like spending the rest of my Saturday night hitting cargo with a rock until it does the right thing.
Reacted by Oscar Gustafsson, ben, Jelmer Vernooij and paullegranddc
Activity
emilio commentedon Sep 6, 2026
I'm confused, it should allow getting syn 3 right?
A minimal test-case would be good, because I just created a directory with those dependencies and I can't reproduce.
ds84182 commentedon Sep 7, 2026
It seems to only happen in my workspace because when I tried making a testcase it doesn't happen. My current workaround is to run
cargo update --ignore-rust-version, but runningcargo addbreaks it again. My rustc version isrustc 1.96.0-nightly (b90dc1e59 2026-03-04).emilio commentedon Sep 7, 2026
Seems like this should move upstream?
chore(deps): cascade prettyplease 0.2.37 → 0.3.0 for bindgen 0.73.2
chore(deps): update rust crate bindgen to v0.73.2 (#43)
djc commentedon Oct 4, 2026
I don't think it's reasonable to expect Cargo's resolver to match up the prettyplease version with the one used by syn necessarily, when another version of bindgen is using old syn + prettyplease. The open PR looks like a proper fix to me:
The current "parallel ranges" approach just seems broken.
build(sapi): turn off the default features of bindgen
Disable unused bindgen default features
austek commentedon Oct 12, 2026
Another real-world hit, in case it helps with the missing test case: a Renovate bump of bindgen 0.72.1 to 0.73.2 in a workspace whose lockfile already had prettyplease 0.2.37 and a syn 3 dependency elsewhere. bindgen 0.73.2 resolved to syn 3.0.5 but kept prettyplease 0.2.37, which uses syn 2, and failed with
the trait bound syn::file::File: syn::parse_quote::ParseQuote is not satisfied.I could not reduce it to a minimal project. A fresh resolve, and adding 0.73.2 next to 0.72.1 in an existing lock (with or without a direct
syn = "3"), both gave a consistent pairing. It needs an existing lock entry plus syn 3 pulled in by another crate.cargo update -p prettypleasefixed it by adding prettyplease 0.3.0 next to 0.2.37. Agree with the comment above: #3506 looks like the proper fix.Disable unused bindgen default features
Use bindgen that fixes codegen for `YGUndefined` (#62)
renovate: ignore prettyplease
renovate: ignore prettyplease
Upgrade comrak to 0.56, rustyline to 19, and zip to 9
chore: go back to bindgen 0.72
ettolrach commentedon Oct 21, 2026
I came across this again when updating rustls-webpki and webpki-root-certs. It's likely others will come across the same issue too, especially with the recent CVEs that were released.
Specifically, have a Cargo.toml file like so:
then run the following commands.
cargo generate-lockfile cargo check --locked cargo update rustls-webpki && cargo update webpki-root-certs cargo check --lockedIt can be fixed by then running
cargo update bindgen.It's ultimately caused by rust-lang/cargo#13942 but I think it should still be fixed in bindgen.
xtqqczze commentedon Oct 28, 2026
I just encountered this issue with
bindgenas a transitive dependency. Manually updatingprettypleasealso resolved it for me.chore(deps): keep prettyplease at 0.2 so the release PR's fips check …
chore(deps): pair bindgen's prettyplease with syn 3
chore(deps): unpin prettyplease so dependency review passes again (#3883
chore(deps): fix the release PR's fips check, which #3883 broke (#3890)
Resolve bindgen to syn 3 to match prettyplease 0.3