Fix additional clippy warnings

This commit fixes a few Clippy warnings that are set to `deny` and
therefore cause CI checks in pull requests to fail.

I verified that `cargo clippy --all-targets --all-features` succeeds
(with no warnings nor errors) after the fixes.

src/annotations/mod.rs

@@ -23,7 +23,7 @@ cfg_if::cfg_if! {
         use std::thread_local;
 
         thread_local! {
-            static ANNOTATION_STATE: RefCell<Option<AnnotationState>> = RefCell::new(None);
+            static ANNOTATION_STATE: RefCell<Option<AnnotationState>> = const { RefCell::new(None) };
         }
 
         #[derive(Clone, Copy, Debug, PartialEq, Eq, Serialize)]
@@ -284,9 +284,11 @@ cfg_if::cfg_if! {
             ANNOTATION_STATE.with(|cell| {
                 let mut bw = cell.borrow_mut();
                 assert!(bw.is_none(), "annotations already started");
-                let mut state: AnnotationState = Default::default();
-                state.version = ANNOTATION_VERSION;
-                state.last_task_id = Some(0.into());
+                let state = AnnotationState {
+                    version: ANNOTATION_VERSION,
+                    last_task_id: Some(0.into()),
+                    ..Default::default()
+                };
                 *bw = Some(state);
             });
         }

src/sync/mpsc.rs

@@ -484,15 +484,15 @@ pub struct IntoIter<T> {
     rx: Receiver<T>,
 }
 
-impl<'a, T> Iterator for Iter<'a, T> {
+impl<T> Iterator for Iter<'_, T> {
     type Item = T;
 
     fn next(&mut self) -> Option<T> {
         self.rx.recv().ok()
     }
 }
 
-impl<'a, T> Iterator for TryIter<'a, T> {
+impl<T> Iterator for TryIter<'_, T> {
     type Item = T;
 
     fn next(&mut self) -> Option<T> {

src/sync/mutex.rs

@@ -177,7 +177,7 @@ impl<'a, T: ?Sized> MutexGuard<'a, T> {
     }
 }
 
-impl<'a, T: ?Sized> Drop for MutexGuard<'a, T> {
+impl<T: ?Sized> Drop for MutexGuard<'_, T> {
     fn drop(&mut self) {
         // Release the inner mutex
         self.inner = None;

tests/demo/bounded_buffer.rs

@@ -1,3 +1,7 @@
+//! This file implements the example from a blog post about Coyote (P#):
+//!   https://cloudblogs.microsoft.com/opensource/2020/07/14/extreme-programming-meets-systematic-testing-using-coyote/
+//! The comments in this file are quotes from that blog post.
+
 // For symmetry we clone some `Arc`s even though we could just move them
 #![allow(clippy::redundant_clone)]
 
@@ -8,10 +12,6 @@ use shuttle::{check_random, replay, thread};
 use std::sync::Arc;
 use test_log::test;
 
-/// This file implements the example from a blog post about Coyote (P#):
-///   https://cloudblogs.microsoft.com/opensource/2020/07/14/extreme-programming-meets-systematic-testing-using-coyote/
-/// The comments in this file are quotes from that blog post.
-
 /// Let’s walk through how Coyote can easily solve the programming problem posed by Tom Cargill. He
 /// shared a BoundedBuffer implementation written in Java with a known, but tricky, deadlock bug.
 ///