Rust 1.86.0 lints (#7254)

Implement lints for the new Rust compiler version 1.86.0.

testing/ef_tests/src/cases.rs

@@ -84,11 +84,11 @@ pub use transition::TransitionTest;
 ///
 /// The feature tests can be run with one of the following methods:
 /// 1. `handler.run_for_feature(feature_name)` for new tests that are not on existing fork, i.e. a
-///     new handler. This will be temporary and the test will need to be updated to use
-///     `handle.run()` once the feature is incorporated into a fork.
+///    new handler. This will be temporary and the test will need to be updated to use
+///    `handle.run()` once the feature is incorporated into a fork.
 /// 2. `handler.run()` for tests that are already on existing forks, but with new test vectors for
-///     the feature. In this case the `handler.is_enabled_for_feature` will need to be implemented
-///     to return `true` for the feature in order for the feature test vector to be tested.
+///    the feature. In this case the `handler.is_enabled_for_feature` will need to be implemented
+///    to return `true` for the feature in order for the feature test vector to be tested.
 #[derive(Debug, PartialEq, Clone, Copy)]
 pub enum FeatureName {
     // TODO(fulu): to be removed once we start using Fulu types for test vectors.

testing/ef_tests/src/cases/fork_choice.rs

@@ -143,7 +143,7 @@ impl<E: EthSpec> LoadCase for ForkChoiceTest<E> {
     fn load_from_dir(path: &Path, fork_name: ForkName) -> Result<Self, Error> {
         let description = path
             .iter()
-            .last()
+            .next_back()
             .expect("path must be non-empty")
             .to_str()
             .expect("path must be valid OsStr")