Add workflows and lints from mullvad/coding-guidelines

.gitcarbon

@@ -1,3 +1,6 @@
+[carbon ".github/workflows/cargo-shear.yml"]
+	sourceRepository = https://github.com/mullvad/coding-guidelines.git
+	sourcePath = rust/.github/workflows/cargo-shear.yml
 [carbon "src/testdata/inclusion-invalid.json"]
 	sourceRepository = https://github.com/rgdd/cctv.git
 	sourcePath = merkle/testdata/inclusion-invalid.json

.github/workflows/cargo-shear.yml

@@ -0,0 +1,23 @@
+---
+name: Unused dependencies
+on:
+  pull_request:
+    paths:
+      - .github/workflows/cargo-shear.yml
+      - "**/*.rs"
+      - "**/Cargo.toml"
+  workflow_dispatch:
+
+permissions: {}
+
+jobs:
+  cargo-shear:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install cargo-shear
+        uses: taiki-e/install-action@cargo-shear
+
+      - name: Run cargo shear
+        run: cargo shear

Cargo.toml

@@ -2,14 +2,13 @@
 name = "sigsum"
 version = "0.2.0"
 edition = "2021"
-license = "MIT"
-homepage = "https://github.com/mullvad/sigsum-rs"
-repository = "https://github.com/mullvad/sigsum-rs"
-documentation = "https://docs.rs/sigsum"
 description = """
 A Rust library for using Sigsum transparency logs.
 """
-
+documentation = "https://docs.rs/sigsum"
+homepage = "https://github.com/mullvad/sigsum-rs"
+repository = "https://github.com/mullvad/sigsum-rs"
+license = "MIT"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
@@ -28,4 +27,27 @@ serde = { version = "1.0.190", features = ["derive"] }
 serde_json = "1.0.107"
 
 [lints.clippy]
+allow_attributes = "warn"
+as_ptr_cast_mut = "warn"
+as_underscore = "warn"
+borrow_as_ptr = "warn"
+implicit_clone = "warn"
 todo = "deny"
+undocumented_unsafe_blocks = "warn"
+unicode_not_nfc = "warn"
+unused_async = "deny"
+wildcard_dependencies = "deny"
+
+[lints.rust]
+absolute_paths_not_starting_with_crate = "deny"
+# Easy to read style and opinionated best practices
+explicit_outlives_requirements = "warn"
+macro_use_extern_crate = "deny"
+missing_abi = "deny"
+# Security
+non_ascii_idents = "forbid"
+# Deny old style Rust
+rust_2018_idioms = { level = "deny", priority = -1 }
+single_use_lifetimes = "warn"
+unused_lifetimes = "warn"
+unused_macro_rules = "warn"

src/io/ascii/mod.rs

@@ -45,7 +45,7 @@ impl SignedTreeHead {
         })
     }
 
-    #[allow(unused_must_use)]
+    #[expect(unused_must_use)]
     pub fn to_ascii(&self) -> String {
         let mut ascii = String::new();
         writeln!(ascii, "{SIZE_FIELD}={}", self.size);
@@ -77,7 +77,7 @@ impl InclusionProof {
         })
     }
 
-    #[allow(unused_must_use)]
+    #[expect(unused_must_use)]
     pub fn to_ascii(&self) -> String {
         let mut ascii = String::new();
         writeln!(ascii, "{LEAF_INDEX_FIELD}={}", self.leaf_index);
@@ -101,7 +101,7 @@ impl Protoleaf {
         })
     }
 
-    #[allow(unused_must_use)]
+    #[expect(unused_must_use)]
     pub fn to_ascii(&self) -> String {
         let mut ascii = String::new();
         writeln!(ascii, "{MESSAGE_FIELD}={:x}", self.message);
@@ -143,7 +143,7 @@ impl SigsumSignature {
         })
     }
 
-    #[allow(unused_must_use)]
+    #[expect(unused_must_use)]
     pub fn to_ascii(&self) -> String {
         let mut ascii = String::new();
         writeln!(ascii, "{VERSION_FIELD}=2");

src/policy/mod.rs

@@ -123,7 +123,7 @@ pub struct Logs<'a> {
     inner: std::collections::hash_map::Iter<'a, Hash, Entity>,
 }
 
-impl<'a> Iterator for Logs<'a> {
+impl Iterator for Logs<'_> {
     type Item = Log;
 
     fn next(&mut self) -> Option<Self::Item> {