Die error_chain, die (#10747)

* Replace error chain for network error

* Fix usages and add manual From impls

* OnDemand Error and remove remaining dependencies

* Die error_chain, die.

* DIE

* Hasta la vista, baby

ethcore/light/src/client/header_chain.rs

@@ -260,7 +260,7 @@ impl HeaderChain {
 			let best_block = {
 				let era = match candidates.get(&curr.best_num) {
 					Some(era) => era,
-					None => bail!("Database corrupt: highest block referenced but no data."),
+					None => return Err("Database corrupt: highest block referenced but no data.".into()),
 				};
 
 				let best = &era.candidates[0];
@@ -582,7 +582,7 @@ impl HeaderChain {
 					} else {
 						let msg = format!("header of block #{} not found in DB ; database in an \
 											inconsistent state", h_num);
-						bail!(msg);
+						return Err(msg.into());
 					};
 
 					let decoded = header.decode().expect("decoding db value failed");

ethcore/light/src/lib.rs

@@ -86,8 +86,7 @@ extern crate keccak_hash as hash;
 extern crate triehash_ethereum as triehash;
 extern crate kvdb;
 extern crate memory_cache;
-#[macro_use]
-extern crate error_chain;
+extern crate derive_more;
 
 #[cfg(test)]
 extern crate kvdb_memorydb;

ethcore/light/src/on_demand/mod.rs

@@ -66,32 +66,31 @@ pub const DEFAULT_NUM_CONSECUTIVE_FAILED_REQUESTS: usize = 1;
 
 /// OnDemand related errors
 pub mod error {
-	// Silence: `use of deprecated item 'std::error::Error::cause': replaced by Error::source, which can support downcasting`
-	// https://github.com/paritytech/parity-ethereum/issues/10302
-	#![allow(deprecated)]
-
 	use futures::sync::oneshot::Canceled;
 
-	error_chain! {
+	/// OnDemand Error
+	#[derive(Debug, derive_more::Display, derive_more::From)]
+	pub enum Error {
+		/// Canceled oneshot channel
+		ChannelCanceled(Canceled),
+		/// Timeout bad response
+		BadResponse(String),
+		/// OnDemand requests limit exceeded
+		#[display(fmt = "OnDemand request maximum backoff iterations exceeded")]
+		RequestLimit,
+	}
 
-		foreign_links {
-			ChannelCanceled(Canceled) #[doc = "Canceled oneshot channel"];
-		}
-
-		errors {
-			#[doc = "Timeout bad response"]
-			BadResponse(err: String) {
-				description("Max response evaluation time exceeded")
-				display("{}", err)
-			}
-
-			#[doc = "OnDemand requests limit exceeded"]
-			RequestLimit {
-				description("OnDemand request maximum backoff iterations exceeded")
-				display("OnDemand request maximum backoff iterations exceeded")
+	impl std::error::Error for Error {
+		fn source(&self) -> Option<&(std::error::Error + 'static)> {
+			match self {
+				Error::ChannelCanceled(err) => Some(err),
+				_ => None,
 			}
 		}
 	}
+
+	/// OnDemand Result
+	pub type Result<T> = std::result::Result<T, Error>;
 }
 
 /// Public interface for performing network requests `OnDemand`
@@ -272,7 +271,7 @@ impl Pending {
 			response_err
 		);
 
-		let err = self::error::ErrorKind::BadResponse(err);
+		let err = self::error::Error::BadResponse(err);
 		if self.sender.send(Err(err.into())).is_err() {
 			debug!(target: "on_demand", "Dropped oneshot channel receiver on no response");
 		}
@@ -280,7 +279,7 @@ impl Pending {
 
 	// returning a peer discovery timeout during query attempts
 	fn request_limit_reached(self) {
-		let err = self::error::ErrorKind::RequestLimit;
+		let err = self::error::Error::RequestLimit;
 		if self.sender.send(Err(err.into())).is_err() {
 			debug!(target: "on_demand", "Dropped oneshot channel receiver on time out");
 		}