ci: raise is-terminal and tempfile dev floors so minimal-versions builds on nightly

[RyanJamesStewart]

The Minimal versions CI job (cargo +nightly update -Zminimal-versions then build and test) is latently broken. Under minimal versions, two dev-dep paths resolve rustix 0.37: codspeed-criterion-compat -> is-terminal 0.4.6 and proptest -> tempfile. rustix below 0.38.6 relies on the rustc_layout_scalar_valid_range_start attribute, which the compiler removed in rust-lang/rust#155433, so it no longer compiles on current nightly (tracked in bytecodealliance/rustix#1620). The job only still passes because it has not re-run on a post-removal nightly.

This raises two dev-dep floors so minimal versions resolves a buildable rustix. is-terminal = "0.4.8" moves the codspeed path off the rustix 0.37 line, and tempfile = "3.9" raises the proptest path to rustix 0.38.26 (the lowest tempfile floor whose rustix builds; tempfile 3.7 and 3.8 still resolve the unbuildable rustix 0.38.0). No direct rustix floor is added, so the normal latest-versions resolution is unchanged and keeps a single rustix.

Verified locally on nightly 2026-05-12:

• with -Zminimal-versions, rustix resolves to a single 0.38.26 and cargo build --workspace plus cargo test --all-features --workspace pass;
• the latest-versions build is unaffected (single rustix 1.1.4, tests pass).

The astral-sh/pubgrub fork hit the same breakage; the fix there (astral-sh#55) was redirected here so the fork can rebase on top.

[konstin]

Can you please share the exact commands that reproduce the breakage? CI on main is clean, and it doesn't reproduce for me locally.

[RyanJamesStewart]

You're right that it doesn't reproduce on dev, and I tracked down why. The minimal-versions job runs the update step with +nightly but builds and tests on stable (cargo build / cargo test), and that split is what keeps it green.

Under -Zminimal-versions, dev resolves a single rustix 0.37.0 (pulled by is-terminal 0.4.6; tempfile minimizes to 3.0.2, which predates rustix, so it adds no rustix path here). rustix 0.37 uses the rustc_layout_scalar_valid_range_start attribute that rust-lang/rust#155433 removed, but only when it is compiled by a nightly rustc. On stable it compiles fine, so the job passes.

Exact commands on a clean dev checkout (nightly 2026-05-12 or later):

cargo +nightly update -Zminimal-versions

# the CI steps, on stable: both pass
cargo build --workspace
cargo test --all-features --workspace

# compile that same dev-dep on nightly: fails
cargo +nightly test --all-features --workspace

The last command gives:

error: cannot find attribute `rustc_layout_scalar_valid_range_start` in this scope
error: could not compile `rustix` (lib) due to 4 previous errors

So the breakage is nightly-only, and the pubgrub-rs job never compiles a dev-dependency on nightly, which is why CI on main is clean. Where I actually hit it was the astral-sh fork, whose minimal-versions job uses cargo +nightly build / cargo +nightly test, so it builds rustix on nightly and fails (fixed on the fork in astral-sh#55).

Given that, this PR is not needed for dev as the job stands today, and I am happy to close it. The one alternative worth flagging: if you would want the minimal-versions job to also catch this class of nightly-only dev-dep rot, switching its build and test steps to +nightly would surface it, and then these floor bumps would be the fix that keeps it green. Your call on whether that is worth it; otherwise I will close.

[konstin]

As nightly is unstable, we shouldn't add fixes specifically for nightly and minimal versions.