Remove unused `trait BorrowedPlainMessage`

There are no uses of this trait inside the crate, so remove it
and transfer the used parts into the `OutboundMessage` inherent impl.

rustls/src/common_state.rs

@@ -8,8 +8,7 @@ use crate::msgs::enums::{AlertLevel, KeyUpdateRequest};
 use crate::msgs::fragmenter::MessageFragmenter;
 use crate::msgs::handshake::CertificateChain;
 use crate::msgs::message::{
-    BorrowedPlainMessage, Message, MessagePayload, OpaqueMessage, OutboundChunks, OutboundMessage,
-    PlainMessage,
+    Message, MessagePayload, OpaqueMessage, OutboundChunks, OutboundMessage, PlainMessage,
 };
 use crate::quic;
 use crate::record_layer;

rustls/src/lib.rs

@@ -440,9 +440,7 @@ pub mod internal {
             };
         }
         pub mod message {
-            pub use crate::msgs::message::{
-                BorrowedPlainMessage, Message, MessagePayload, OpaqueMessage, PlainMessage,
-            };
+            pub use crate::msgs::message::{Message, MessagePayload, OpaqueMessage, PlainMessage};
         }
         pub mod persist {
             pub use crate::msgs::persist::ServerSessionValue;

rustls/src/msgs/deframer.rs

@@ -698,7 +698,7 @@ mod tests {
     use std::io;
 
     use crate::crypto::cipher::PlainMessage;
-    use crate::msgs::message::{BorrowedPlainMessage, Message};
+    use crate::msgs::message::Message;
 
     use super::*;
 

rustls/src/msgs/fragmenter.rs

@@ -101,9 +101,7 @@ mod tests {
     use crate::enums::ContentType;
     use crate::enums::ProtocolVersion;
     use crate::msgs::base::Payload;
-    use crate::msgs::message::{
-        BorrowedPlainMessage, OutboundChunks, OutboundMessage, PlainMessage,
-    };
+    use crate::msgs::message::{OutboundChunks, OutboundMessage, PlainMessage};
 
     fn msg_eq(
         m: &OutboundMessage,

rustls/src/msgs/message.rs

@@ -446,23 +446,14 @@ impl InboundMessage<'_> {
     pub(crate) fn is_valid_ccs(&self) -> bool {
         self.typ == ContentType::ChangeCipherSpec && self.payload == [0x01]
     }
-}
 
-impl BorrowedPlainMessage for InboundMessage<'_> {
-    fn payload_to_vec(&self) -> Vec<u8> {
-        self.payload.to_vec()
-    }
-
-    fn payload_len(&self) -> usize {
-        self.payload.len()
-    }
-
-    fn typ(&self) -> ContentType {
-        self.typ
-    }
-
-    fn version(&self) -> ProtocolVersion {
-        self.version
+    #[cfg(test)]
+    pub(crate) fn into_owned(self) -> PlainMessage {
+        PlainMessage {
+            version: self.version,
+            typ: self.typ,
+            payload: Payload::Owned(self.payload.to_vec()),
+        }
     }
 }
 
@@ -482,53 +473,18 @@ pub struct OutboundMessage<'a> {
     pub payload: OutboundChunks<'a>,
 }
 
-impl BorrowedPlainMessage for OutboundMessage<'_> {
-    fn payload_to_vec(&self) -> Vec<u8> {
-        self.payload.to_vec()
+impl OutboundMessage<'_> {
+    pub(crate) fn encoded_len(&self, record_layer: &RecordLayer) -> usize {
+        OpaqueMessage::HEADER_SIZE as usize + record_layer.encrypted_len(self.payload.len())
     }
 
-    fn payload_len(&self) -> usize {
-        self.payload.len()
-    }
-
-    fn typ(&self) -> ContentType {
-        self.typ
-    }
-
-    fn version(&self) -> ProtocolVersion {
-        self.version
-    }
-}
-
-/// Abstract both inbound and outbound variants of a plaintext message
-pub trait BorrowedPlainMessage: Sized {
-    fn into_owned(self) -> PlainMessage {
-        PlainMessage {
-            version: self.version(),
-            typ: self.typ(),
-            payload: Payload::Owned(self.payload_to_vec()),
-        }
-    }
-
-    fn to_unencrypted_opaque(&self) -> OpaqueMessage {
+    pub(crate) fn to_unencrypted_opaque(&self) -> OpaqueMessage {
         OpaqueMessage {
-            version: self.version(),
-            typ: self.typ(),
-            payload: Payload::Owned(self.payload_to_vec()),
+            version: self.version,
+            typ: self.typ,
+            payload: Payload::Owned(self.payload.to_vec()),
         }
     }
-
-    fn encoded_len(&self, record_layer: &RecordLayer) -> usize {
-        OpaqueMessage::HEADER_SIZE as usize + record_layer.encrypted_len(self.payload_len())
-    }
-
-    fn payload_to_vec(&self) -> Vec<u8>;
-
-    fn payload_len(&self) -> usize;
-
-    fn typ(&self) -> ContentType;
-
-    fn version(&self) -> ProtocolVersion;
 }
 
 #[derive(Debug, Clone)]