Relax impls for [T; 0]

serde/src/de/impls.rs

@@ -625,9 +625,7 @@ impl<A> ArrayVisitor<A> {
     }
 }
 
-impl<'de, T> Visitor<'de> for ArrayVisitor<[T; 0]>
-    where T: Deserialize<'de>
-{
+impl<'de, T> Visitor<'de> for ArrayVisitor<[T; 0]> {
     type Value = [T; 0];
 
     fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
@@ -642,9 +640,8 @@ impl<'de, T> Visitor<'de> for ArrayVisitor<[T; 0]>
     }
 }
 
-impl<'de, T> Deserialize<'de> for [T; 0]
-    where T: Deserialize<'de>
-{
+// Does not require T: Deserialize<'de>.
+impl<'de, T> Deserialize<'de> for [T; 0] {
     fn deserialize<D>(deserializer: D) -> Result<[T; 0], D::Error>
         where D: Deserializer<'de>
     {

serde/src/ser/impls.rs

@@ -143,6 +143,16 @@ impl<T> Serialize for PhantomData<T> {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+// Does not require T: Serialize.
+impl<T> Serialize for [T; 0] {
+    #[inline]
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        try!(serializer.serialize_seq_fixed_size(0)).end()
+    }
+}
+
 macro_rules! array_impls {
     ($len:expr) => {
         impl<T> Serialize for [T; $len] where T: Serialize {
@@ -160,7 +170,6 @@ macro_rules! array_impls {
     }
 }
 
-array_impls!(0);
 array_impls!(1);
 array_impls!(2);
 array_impls!(3);

test_suite/tests/test_gen.rs

@@ -295,6 +295,11 @@ fn test_gen() {
     #[derive(Serialize, Deserialize)]
     #[serde(deny_unknown_fields)]
     struct UnitDenyUnknown;
+
+    #[derive(Serialize, Deserialize)]
+    struct EmptyArray {
+        empty: [X; 0],
+    }
 }
 
 //////////////////////////////////////////////////////////////////////////