Merge pull request #2334 from dtolnay/mapimpl

Reduce trait bounds in HashMap and BTreeMap serialize

serde/src/ser/impls.rs

@@ -365,7 +365,26 @@ tuple_impls! {
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(any(feature = "std", feature = "alloc"))]
+#[cfg(all(any(feature = "std", feature = "alloc"), not(no_relaxed_trait_bounds)))]
+macro_rules! map_impl {
+    ($ty:ident < K $(: $kbound1:ident $(+ $kbound2:ident)*)*, V $(, $typaram:ident : $bound:ident)* >) => {
+        impl<K, V $(, $typaram)*> Serialize for $ty<K, V $(, $typaram)*>
+        where
+            K: Serialize,
+            V: Serialize,
+        {
+            #[inline]
+            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+            where
+                S: Serializer,
+            {
+                serializer.collect_map(self)
+            }
+        }
+    }
+}
+
+#[cfg(all(any(feature = "std", feature = "alloc"), no_relaxed_trait_bounds))]
 macro_rules! map_impl {
     ($ty:ident < K $(: $kbound1:ident $(+ $kbound2:ident)*)*, V $(, $typaram:ident : $bound:ident)* >) => {
         impl<K, V $(, $typaram)*> Serialize for $ty<K, V $(, $typaram)*>