From 44e291ee09239f899506b5d764cbca225e3d1bcb Mon Sep 17 00:00:00 2001
From: WaterWhisperer <waterwhisperer24@qq.com>
Date: Fri, 12 Jun 2026 20:59:32 +0800
Subject: [PATCH] prost: relax codec Default bounds

Manually implement Default for ProstEncoder and ProstDecoder so their
message types do not need to implement Default.

Fixes: #2458
---
 tonic-prost/src/codec.rs | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/tonic-prost/src/codec.rs b/tonic-prost/src/codec.rs
index f25bb6d43..8418fe5ae 100644
--- a/tonic-prost/src/codec.rs
+++ b/tonic-prost/src/codec.rs
@@ -74,7 +74,7 @@ where
 }
 
 /// A [`Encoder`] that knows how to encode `T`.
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone)]
 pub struct ProstEncoder<T> {
     _pd: PhantomData<T>,
     buffer_settings: BufferSettings,
@@ -90,6 +90,12 @@ impl<T> ProstEncoder<T> {
     }
 }
 
+impl<T> Default for ProstEncoder<T> {
+    fn default() -> Self {
+        Self::new(Default::default())
+    }
+}
+
 impl<T: Message> Encoder for ProstEncoder<T> {
     type Item = T;
     type Error = Status;
@@ -107,7 +113,7 @@ impl<T: Message> Encoder for ProstEncoder<T> {
 }
 
 /// A [`Decoder`] that knows how to decode `U`.
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone)]
 pub struct ProstDecoder<U> {
     _pd: PhantomData<U>,
     buffer_settings: BufferSettings,
@@ -123,6 +129,12 @@ impl<U> ProstDecoder<U> {
     }
 }
 
+impl<U> Default for ProstDecoder<U> {
+    fn default() -> Self {
+        Self::new(Default::default())
+    }
+}
+
 impl<U: Message + Default> Decoder for ProstDecoder<U> {
     type Item = U;
     type Error = Status;