diff --git a/tonic/src/client/grpc.rs b/tonic/src/client/grpc.rs
index 0df98a2..db47173 100644
--- a/tonic/src/client/grpc.rs
+++ b/tonic/src/client/grpc.rs
@@ -93,7 +93,7 @@ impl<T> Grpc<T> {
         let message = body
             .try_next()
             .await?
-            .ok_or(Status::new(Code::Internal, "Missing response message."))?;
+            .ok_or_else(|| Status::new(Code::Internal, "Missing response message."))?;
 
         if let Some(trailers) = body.trailers().await? {
             parts.merge(trailers);
diff --git a/tonic/src/codec/encode.rs b/tonic/src/codec/encode.rs
index 5029334..bfa269a 100644
--- a/tonic/src/codec/encode.rs
+++ b/tonic/src/codec/encode.rs
@@ -117,7 +117,7 @@ where
     }
 
     fn poll_data(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         cx: &mut Context<'_>,
     ) -> Poll<Option<Result<Self::Data, Self::Error>>> {
         let mut self_proj = self.project();
@@ -135,7 +135,7 @@ where
     }
 
     fn poll_trailers(
-        mut self: Pin<&mut Self>,
+        self: Pin<&mut Self>,
         _cx: &mut Context<'_>,
     ) -> Poll<Result<Option<HeaderMap>, Status>> {
         match self.role {
diff --git a/tonic/src/metadata/encoding.rs b/tonic/src/metadata/encoding.rs
index 41bbb40..69cfbd0 100644
--- a/tonic/src/metadata/encoding.rs
+++ b/tonic/src/metadata/encoding.rs
@@ -150,7 +150,7 @@ impl self::value_encoding::Sealed for Binary {
         if decoded_a.is_ok() && decoded_b.is_ok() {
             decoded_a.unwrap() == decoded_b.unwrap()
         } else {
-            !decoded_a.is_ok() && !decoded_b.is_ok()
+            decoded_a.is_err() && decoded_b.is_err()
         }
     }
 
diff --git a/tonic/src/metadata/map.rs b/tonic/src/metadata/map.rs
index 36483da..5a28e0e 100644
--- a/tonic/src/metadata/map.rs
+++ b/tonic/src/metadata/map.rs
@@ -1265,7 +1265,7 @@ impl<'a, VE: ValueEncoding> Iterator for ValueDrain<'a, VE> {
     fn next(&mut self) -> Option<Self::Item> {
         self.inner
             .next()
-            .map(|value| MetadataValue::unchecked_from_header_value(value))
+            .map(MetadataValue::unchecked_from_header_value)
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
diff --git a/tonic/src/metadata/value.rs b/tonic/src/metadata/value.rs
index 072003e..c96f24f 100644
--- a/tonic/src/metadata/value.rs
+++ b/tonic/src/metadata/value.rs
@@ -362,7 +362,7 @@ impl MetadataValue<Ascii> {
     /// assert_eq!(val.to_str().unwrap(), "hello");
     /// ```
     pub fn to_str(&self) -> Result<&str, ToStrError> {
-        return self.inner.to_str().map_err(|_| ToStrError::new());
+        self.inner.to_str().map_err(|_| ToStrError::new())
     }
 
     /// Converts a `MetadataValue` to a byte slice. For Binary values, use
@@ -628,7 +628,7 @@ impl<VE: ValueEncoding> PartialOrd<MetadataValue<VE>> for [u8] {
 impl<VE: ValueEncoding> PartialEq<String> for MetadataValue<VE> {
     #[inline]
     fn eq(&self, other: &String) -> bool {
-        *self == &other[..]
+        *self == other[..]
     }
 }
 
diff --git a/tonic/src/server/grpc.rs b/tonic/src/server/grpc.rs
index b7474c9..3653c79 100644
--- a/tonic/src/server/grpc.rs
+++ b/tonic/src/server/grpc.rs
@@ -142,7 +142,7 @@ where
         let message = stream
             .try_next()
             .await?
-            .ok_or(Status::new(Code::Internal, "Missing request message."))?;
+            .ok_or_else(|| Status::new(Code::Internal, "Missing request message."))?;
 
         let mut req = Request::from_http_parts(parts, message);
 
diff --git a/tonic/src/transport/server.rs b/tonic/src/transport/server.rs
index 16875f7..41c6780 100644
--- a/tonic/src/transport/server.rs
+++ b/tonic/src/transport/server.rs
@@ -142,7 +142,7 @@ impl Server {
             let f = f.clone();
             tower::service_fn(move |req| f(&mut s, req))
         });
-        let layer = Stack::new(interceptor, layer_fn(|s| BoxService::new(s)));
+        let layer = Stack::new(interceptor, layer_fn(BoxService::new));
         self.interceptor = Some(Arc::new(layer));
         self
     }
@@ -159,7 +159,7 @@ impl Server {
         S::Error: Into<crate::Error> + Send,
     {
         let interceptor = self.interceptor.clone();
-        let concurrency_limit = self.concurrency_limit.clone();
+        let concurrency_limit = self.concurrency_limit;
         // let timeout = self.timeout.clone();
 
         let incoming = hyper::server::accept::from_stream(async_stream::try_stream! {
@@ -280,7 +280,7 @@ where
     fn call(&mut self, _: T) -> Self::Future {
         let interceptor = self.interceptor.clone();
         let make = self.inner.make_service(());
-        let concurrency_limit = self.concurrency_limit.clone();
+        let concurrency_limit = self.concurrency_limit;
         // let timeout = self.timeout.clone();
 
         Box::pin(async move {
diff --git a/tonic/src/transport/service/connection.rs b/tonic/src/transport/service/connection.rs
index f9fc58b..2737dbc 100644
--- a/tonic/src/transport/service/connection.rs
+++ b/tonic/src/transport/service/connection.rs
@@ -38,11 +38,11 @@ impl Connection {
 
         let stack = ServiceBuilder::new()
             .layer_fn(|s| AddOrigin::new(s, endpoint.uri.clone()))
-            .optional_layer(endpoint.timeout.map(|t| TimeoutLayer::new(t)))
+            .optional_layer(endpoint.timeout.map(TimeoutLayer::new))
             .optional_layer(
                 endpoint
                     .concurrency_limit
-                    .map(|l| ConcurrencyLimitLayer::new(l)),
+                    .map(ConcurrencyLimitLayer::new),
             )
             .optional_layer(endpoint.rate_limit.map(|(l, d)| RateLimitLayer::new(l, d)))
             .into_inner();
diff --git a/tonic/src/transport/service/layer.rs b/tonic/src/transport/service/layer.rs
index d3aec3d..4d32688 100644
--- a/tonic/src/transport/service/layer.rs
+++ b/tonic/src/transport/service/layer.rs
@@ -30,7 +30,7 @@ impl<L> ServiceBuilderExt<L> for ServiceBuilder<L> {
         F: Fn(S) -> Out,
     {
         let layer = OptionalLayer {
-            inner: f.map(|f| LayerFn(f)),
+            inner: f.map(LayerFn),
         };
 
         self.layer(layer)