Fix memofs clippy lints (#682)

The third in a series of PRs that aim to get CI passing

crates/memofs/src/in_memory_fs.rs

@@ -50,6 +50,12 @@ impl InMemoryFs {
     }
 }
 
+impl Default for InMemoryFs {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 #[derive(Debug)]
 struct InMemoryFsInner {
     entries: HashMap<PathBuf, Entry>,

crates/memofs/src/lib.rs

@@ -194,11 +194,8 @@ impl VfsInner {
     }
 
     fn commit_event(&mut self, event: &VfsEvent) -> io::Result<()> {
-        match event {
-            VfsEvent::Remove(path) => {
-                let _ = self.backend.unwatch(&path);
-            }
-            _ => {}
+        if let VfsEvent::Remove(path) = event {
+            let _ = self.backend.unwatch(path);
         }
 
         Ok(())

crates/memofs/src/noop_backend.rs

@@ -74,3 +74,9 @@ impl VfsBackend for NoopBackend {
         ))
     }
 }
+
+impl Default for NoopBackend {
+    fn default() -> Self {
+        Self::new()
+    }
+}

crates/memofs/src/std_backend.rs

@@ -108,3 +108,9 @@ impl VfsBackend for StdBackend {
             .map_err(|inner| io::Error::new(io::ErrorKind::Other, inner))
     }
 }
+
+impl Default for StdBackend {
+    fn default() -> Self {
+        Self::new()
+    }
+}