xxx: Backup

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

subxt/src/rpc/types.rs

@@ -507,15 +507,46 @@ pub enum FollowEvent<Hash> {
 /// The result of a chain head method.
 #[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
 #[serde(rename_all = "camelCase")]
+#[cfg(feature = "experimental-light-client")]
+#[serde(try_from = "LightClientChainHeadResult<T>")]
 pub struct ChainHeadResult<T> {
     /// Result of the method.
     #[cfg(not(feature = "experimental-light-client"))]
     pub result: T,
     /// Result of the method.
+    ///
+    /// # Note
+    ///
+    /// `chainHead_body` returns a vector of values, while
+    /// `chainHead_storage` returns just one plain element.
     #[cfg(feature = "experimental-light-client")]
     pub value: Vec<T>,
 }
 
+/// The result of a chain head method.
+#[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
+#[serde(rename_all = "camelCase")]
+#[cfg(feature = "experimental-light-client")]
+pub struct LightClientChainHeadResult<T> {
+    /// Result of the method.
+    ///
+    /// # Note
+    ///
+    /// `chainHead_body` returns a vector of values, while
+    /// `chainHead_storage` returns just one plain element.
+    pub value: T,
+}
+
+impl<T> TryFrom<LightClientChainHeadResult<T>> for ChainHeadResult<T> {
+    type Error = &'static str;
+
+    fn try_from(light: LightClientChainHeadResult<T>) -> Result<Self, &'static str> {
+        Ok(Self {
+            value: vec![light.value],
+        })
+    }
+}
+
 /// The event generated by the body / call / storage methods.
 #[derive(Debug, Clone, PartialEq, Eq, Deserialize)]
 #[serde(rename_all = "camelCase")]