Introduce a cargo clippy run

Personally, I don’t always agree with Clippy, but it a very widely
recommended tool for writing idiomatic Rust. So on balance, I think
it’s overall a good idea to enable it for both our exercises and our
tooling.

mdbook-course/src/bin/course-schedule.rs

@@ -48,7 +48,7 @@ fn timediff(actual: u64, target: u64, slop: u64) -> String {
     } else if actual + slop < target {
         format!("{}: ({} short)", duration(actual), duration(target - actual),)
     } else {
-        format!("{}", duration(actual))
+        duration(actual).to_string()
     }
 }
 

mdbook-course/src/bin/mdbook-course.rs

@@ -29,7 +29,7 @@ fn main() {
         );
     let matches = app.get_matches();
 
-    if let Some(_) = matches.subcommand_matches("supports") {
+    if matches.subcommand_matches("supports").is_some() {
         // Support all renderers.
         process::exit(0);
     }

mdbook-course/src/course.rs

@@ -156,7 +156,7 @@ impl Courses {
     fn course_mut(&mut self, name: impl AsRef<str>) -> &mut Course {
         let name = name.as_ref();
         if let Some(found_idx) =
-            self.courses.iter().position(|course| &course.name == name)
+            self.courses.iter().position(|course| course.name == name)
         {
             return &mut self.courses[found_idx];
         }
@@ -177,9 +177,7 @@ impl Courses {
         &self,
         chapter: &Chapter,
     ) -> Option<(&Course, &Session, &Segment, &Slide)> {
-        let Some(ref source_path) = chapter.source_path else {
-            return None;
-        };
+        let source_path = chapter.source_path.as_ref()?;
 
         for course in self {
             for session in course {
@@ -193,7 +191,7 @@ impl Courses {
             }
         }
 
-        return None;
+        None
     }
 }
 
@@ -202,7 +200,7 @@ impl<'a> IntoIterator for &'a Courses {
     type IntoIter = std::slice::Iter<'a, Course>;
 
     fn into_iter(self) -> Self::IntoIter {
-        (&self.courses).into_iter()
+        self.courses.iter()
     }
 }
 
@@ -216,7 +214,7 @@ impl Course {
     fn session_mut(&mut self, name: impl AsRef<str>) -> &mut Session {
         let name = name.as_ref();
         if let Some(found_idx) =
-            self.sessions.iter().position(|session| &session.name == name)
+            self.sessions.iter().position(|session| session.name == name)
         {
             return &mut self.sessions[found_idx];
         }
@@ -275,7 +273,7 @@ impl<'a> IntoIterator for &'a Course {
     type IntoIter = std::slice::Iter<'a, Session>;
 
     fn into_iter(self) -> Self::IntoIter {
-        (&self.sessions).into_iter()
+        self.sessions.iter()
     }
 }
 
@@ -350,7 +348,7 @@ impl<'a> IntoIterator for &'a Session {
     type IntoIter = std::slice::Iter<'a, Segment>;
 
     fn into_iter(self) -> Self::IntoIter {
-        (&self.segments).into_iter()
+        self.segments.iter()
     }
 }
 
@@ -403,7 +401,7 @@ impl<'a> IntoIterator for &'a Segment {
     type IntoIter = std::slice::Iter<'a, Slide>;
 
     fn into_iter(self) -> Self::IntoIter {
-        (&self.slides).into_iter()
+        self.slides.iter()
     }
 }
 
@@ -451,7 +449,7 @@ impl Slide {
     pub fn is_sub_chapter(&self, chapter: &Chapter) -> bool {
         // The first `source_path` in the slide is the "parent" chapter, so anything
         // else is a sub-chapter.
-        chapter.source_path.as_ref() != self.source_paths.get(0)
+        chapter.source_path.as_ref() != self.source_paths.first()
     }
 
     /// Return the total duration of this slide.

mdbook-course/src/markdown.rs

@@ -83,7 +83,7 @@ impl<const N: usize> Table<N> {
         for cell in iter {
             write!(f, " {} |", cell)?;
         }
-        write!(f, "\n")
+        writeln!(f)
     }
 }
 

mdbook-course/src/replacements.rs

@@ -50,7 +50,7 @@ pub fn replace(
                 }
                 ["course", "outline", course_name] => {
                     let Some(course) = courses.find_course(course_name) else {
-                        return format!("not found - {}", captures[0].to_string());
+                        return format!("not found - {}", &captures[0]);
                     };
                     course.schedule()
                 }