chore: fix the Clippy and minimal-versions jobs on Rust 1.91

Both jobs have been red on `main` since the 1.91 toolchain reached the runners, independently of any pull request.

Clippy 1.91 extended `collapsible_if` to nested `if let`, which flags 40 sites. `cargo clippy --fix` rewrites them as let-chains, but neither stable rustfmt nor nightly 1.10.0 reformats the result, so the bodies keep their pre-collapse indentation until each site is fixed by hand. That churn lands in the session and encrypted modules that most open PRs touch, so allow the lint for now next to the two allows already in `lib.rs`.

Under minimal versions, `yasna`'s `num-bigint = "0.4"` resolves to 0.4.0, whose `bits().div_ceil(&u64::from(bits))` now picks the inherent `u64::div_ceil` over `Integer::div_ceil` and fails to compile. 0.4.6 switched those three call sites to UFCS, so raise the floor with a renamed optional dependency, the same way `cipher`, `ghash`, `polyval` and `universal-hash` are already pinned in this file.

Verified with the CI commands: `cargo clippy` with and without `--all-features`, `cargo minimal-versions check --all-features --no-dev-deps`, `cargo fmt --check`, `cargo test --all-features`, plus the 1.89.0 `wasm32-wasip1` build and an MSRV check.

Author: inureyes

russh/Cargo.toml

@@ -17,7 +17,7 @@ default = ["flate2", "aws-lc-rs", "rsa"]
 # Crypto backends: enable at least one of `aws-lc-rs` or `ring`.
 aws-lc-rs = ["dep:aws-lc-rs"] # Default crypto backend.
 async-trait = ["dep:async-trait"]
-legacy-ed25519-pkcs8-parser = ["yasna"]
+legacy-ed25519-pkcs8-parser = ["yasna", "num-bigint-04"]
 # Danger: 3DES cipher is insecure.
 des = ["dep:des"]
 # Danger: DSA algorithm is insecure.
@@ -63,6 +63,10 @@ md5 = "0.8"
 ml-kem = "0.3"
 module-lattice = "0.2"
 num-bigint = { version = "0.5", features = ["rand_0_10"] }
+# `yasna` accepts any num-bigint 0.4; only listed to raise the floor, because
+# a cargo-minimal-versions failure below 0.4.6 resolves `div_ceil` to the
+# inherent `u64::div_ceil` instead of `Integer::div_ceil`.
+num-bigint-04 = { package = "num-bigint", version = "0.4.6", optional = true }
 p256 = { version = "0.14", features = ["ecdh"] }
 p384 = { version = "0.14", features = ["ecdh"] }
 p521 = { version = "0.14", features = ["ecdh"] }

russh/src/lib.rs

@@ -4,7 +4,13 @@
     clippy::indexing_slicing,
     clippy::panic
 )]
-#![allow(clippy::single_match, clippy::upper_case_acronyms)]
+// Rust 1.91 extended `collapsible_if` to suggest let-chains, which rustfmt
+// does not yet format; revisit once it does.
+#![allow(
+    clippy::collapsible_if,
+    clippy::single_match,
+    clippy::upper_case_acronyms
+)]
 #![allow(macro_expanded_macro_exports_accessed_by_absolute_paths)]
 // length checked
 // Copyright 2016 Pierre-Étienne Meunier