chore: Use derive macro to implement default (#1762)

tonic-web/src/client.rs

@@ -15,21 +15,15 @@ use crate::call::content_types::GRPC_WEB;
 use crate::call::GrpcWebCall;
 
 /// Layer implementing the grpc-web protocol for clients.
-#[derive(Debug, Clone)]
+#[derive(Debug, Default, Clone)]
 pub struct GrpcWebClientLayer {
     _priv: (),
 }
 
 impl GrpcWebClientLayer {
     /// Create a new grpc-web for clients layer.
     pub fn new() -> GrpcWebClientLayer {
-        Self { _priv: () }
-    }
-}
-
-impl Default for GrpcWebClientLayer {
-    fn default() -> Self {
-        Self::new()
+        Self::default()
     }
 }
 

tonic-web/src/layer.rs

@@ -4,21 +4,15 @@ use tower_layer::Layer;
 use tower_service::Service;
 
 /// Layer implementing the grpc-web protocol.
-#[derive(Debug, Clone)]
+#[derive(Debug, Default, Clone)]
 pub struct GrpcWebLayer {
     _priv: (),
 }
 
 impl GrpcWebLayer {
     /// Create a new grpc-web layer.
     pub fn new() -> GrpcWebLayer {
-        Self { _priv: () }
-    }
-}
-
-impl Default for GrpcWebLayer {
-    fn default() -> Self {
-        Self::new()
+        Self::default()
     }
 }
 

tonic/src/codec/compression.rs

@@ -276,19 +276,14 @@ pub(crate) fn decompress(
     Ok(())
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
 pub(crate) enum SingleMessageCompressionOverride {
     /// Inherit whatever compression is already configured. If the stream is compressed this
     /// message will also be configured.
     ///
     /// This is the default.
+    #[default]
     Inherit,
     /// Don't compress this message, even if compression is enabled on the stream.
     Disable,
 }
-
-impl Default for SingleMessageCompressionOverride {
-    fn default() -> Self {
-        Self::Inherit
-    }
-}

tonic/src/metadata/key.rs

@@ -24,7 +24,7 @@ pub struct MetadataKey<VE: ValueEncoding> {
 }
 
 /// A possible error when converting a `MetadataKey` from another type.
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct InvalidMetadataKey {
     _priv: (),
 }
@@ -180,7 +180,7 @@ impl<VE: ValueEncoding> fmt::Display for MetadataKey<VE> {
 impl InvalidMetadataKey {
     #[doc(hidden)]
     pub fn new() -> InvalidMetadataKey {
-        InvalidMetadataKey { _priv: () }
+        Self::default()
     }
 }
 
@@ -275,12 +275,6 @@ impl fmt::Display for InvalidMetadataKey {
     }
 }
 
-impl Default for InvalidMetadataKey {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 impl Error for InvalidMetadataKey {}
 
 #[cfg(test)]