locktime: unify serde impls

bitcoin/src/blockdata/locktime/absolute.rs

@@ -179,8 +179,6 @@ impl fmt::UpperHex for PackedLockTime {
 /// ```
 #[allow(clippy::derive_ord_xor_partial_ord)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-#[cfg_attr(feature = "serde", serde(crate = "actual_serde"))]
 pub enum LockTime {
     /// A block height lock time value.
     ///
@@ -440,6 +438,44 @@ impl Decodable for LockTime {
     }
 }
 
+#[cfg(feature = "serde")]
+impl serde::Serialize for LockTime {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_u32(self.to_consensus_u32())
+    }
+}
+
+#[cfg(feature = "serde")]
+impl<'de> serde::Deserialize<'de> for LockTime {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        struct Visitor;
+        impl<'de> serde::de::Visitor<'de> for Visitor {
+            type Value = u32;
+            fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str("a u32") }
+            // We cannot just implement visit_u32 because JSON (among other things) always
+            // calls visit_u64, even when called from Deserializer::deserialize_u32. The
+            // other visit_u*s have default implementations that forward to visit_u64.
+            fn visit_u64<E: serde::de::Error>(self, v: u64) -> Result<u32, E> {
+                use core::convert::TryInto;
+                v.try_into().map_err(|_| E::invalid_value(serde::de::Unexpected::Unsigned(v), &"a 32-bit number"))
+            }
+            // Also do the signed version, just for good measure.
+            fn visit_i64<E: serde::de::Error>(self, v: i64) -> Result<u32, E> {
+                use core::convert::TryInto;
+                v.try_into().map_err(|_| E::invalid_value(serde::de::Unexpected::Signed(v), &"a 32-bit number"))
+            }
+        }
+        deserializer.deserialize_u32(Visitor).map(LockTime::from_consensus)
+    }
+}
+
+
 /// An absolute block height, guaranteed to always contain a valid height value.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]