rpc-api: use thiserror instead of derive_more for error handling (#9631)

Signed-off-by: koushiro <koushiro.cqx@gmail.com>

substrate/client/rpc-api/src/state/error.rs

@@ -28,13 +28,13 @@ pub type Result<T> = std::result::Result<T, Error>;
 pub type FutureResult<T> = jsonrpc_core::BoxFuture<Result<T>>;
 
 /// State RPC errors.
-#[derive(Debug, derive_more::Display, derive_more::From)]
+#[derive(Debug, thiserror::Error)]
 pub enum Error {
 	/// Client error.
-	#[display(fmt = "Client error: {}", _0)]
-	Client(Box<dyn std::error::Error + Send>),
+	#[error("Client error: {}", .0)]
+	Client(#[from] Box<dyn std::error::Error + Send>),
 	/// Provided block range couldn't be resolved to a list of blocks.
-	#[display(fmt = "Cannot resolve a block range ['{:?}' ... '{:?}]. {}", from, to, details)]
+	#[error("Cannot resolve a block range ['{:?}' ... '{:?}]. {}", .from, .to, .details)]
 	InvalidBlockRange {
 		/// Beginning of the block range.
 		from: String,
@@ -44,7 +44,7 @@ pub enum Error {
 		details: String,
 	},
 	/// Provided count exceeds maximum value.
-	#[display(fmt = "count exceeds maximum value. value: {}, max: {}", value, max)]
+	#[error("count exceeds maximum value. value: {}, max: {}", .value, .max)]
 	InvalidCount {
 		/// Provided value
 		value: u32,
@@ -52,16 +52,8 @@ pub enum Error {
 		max: u32,
 	},
 	/// Call to an unsafe RPC was denied.
-	UnsafeRpcCalled(crate::policy::UnsafeRpcError),
-}
-
-impl std::error::Error for Error {
-	fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-		match self {
-			Error::Client(ref err) => Some(&**err),
-			_ => None,
-		}
-	}
+	#[error(transparent)]
+	UnsafeRpcCalled(#[from] crate::policy::UnsafeRpcError),
 }
 
 /// Base code for all state errors.