Make decl_error! errors usable (#4449)

* Make `decl_error!` errors usable

This pr implements support for returning errors of different pallets in
a pallet. These errors need to be declared with `decl_error!`.

The pr changes the following:

- Each dispatchable function now returns a `DispatchResult` which is an
alias for `Result<(), DispatchError>`.
- `DispatchError` is an enum that has 4 variants:
  - `Other`: For storing string error messages
  - `CannotLookup`: Variant that is returned when something returns a
  `sp_runtime::LookupError`
  - `BadOrigin`: Variant that is returned for any kind of bad origin
  - `Module`: The error of a specific module. Contains the `index`,
  `error` and the `message`. The index is the index of the module in
  `construct_runtime!`. `error` is the index of the error in the error
  enum declared by `decl_error!`. `message` is the message to the error
  variant (this will not be encoded).
- `construct_runtime!` now creates a new struct `ModuleToIndex`. This
struct implements the trait `ModuleToIndex`.
- `frame_system::Trait` has a new associated type: `ModuleToIndex` that
expects the `ModuleToIndex` generated by `construct_runtime!`.
- All error strings returned in any module are being converted now to `DispatchError`.
- `BadOrigin` is the default error returned by any type that implements `EnsureOrigin`.

* Fix frame system benchmarks

substrate/frame/contracts/src/lib.rs

@@ -119,7 +119,7 @@ use sp_runtime::{
 	},
 	RuntimeDebug,
 };
-use frame_support::dispatch::{Result, Dispatchable};
+use frame_support::dispatch::{DispatchResult, Dispatchable};
 use frame_support::{
 	Parameter, decl_module, decl_event, decl_storage, storage::child,
 	parameter_types, IsSubType,
@@ -539,10 +539,10 @@ decl_module! {
 		/// Updates the schedule for metering contracts.
 		///
 		/// The schedule must have a greater version than the stored schedule.
-		pub fn update_schedule(origin, schedule: Schedule) -> Result {
+		pub fn update_schedule(origin, schedule: Schedule) -> DispatchResult {
 			ensure_root(origin)?;
 			if <Module<T>>::current_schedule().version >= schedule.version {
-				return Err("new schedule must have a greater version than current");
+				Err("new schedule must have a greater version than current")?
 			}
 
 			Self::deposit_event(RawEvent::ScheduleUpdated(schedule.version));
@@ -557,7 +557,7 @@ decl_module! {
 			origin,
 			#[compact] gas_limit: Gas,
 			code: Vec<u8>
-		) -> Result {
+		) -> DispatchResult {
 			let origin = ensure_signed(origin)?;
 
 			let (mut gas_meter, imbalance) = gas::buy_gas::<T>(&origin, gas_limit)?;
@@ -570,7 +570,7 @@ decl_module! {
 
 			gas::refund_unused_gas::<T>(&origin, gas_meter, imbalance);
 
-			result.map(|_| ())
+			result.map(|_| ()).map_err(Into::into)
 		}
 
 		/// Makes a call to an account, optionally transferring some balance.
@@ -586,13 +586,13 @@ decl_module! {
 			#[compact] value: BalanceOf<T>,
 			#[compact] gas_limit: Gas,
 			data: Vec<u8>
-		) -> Result {
+		) -> DispatchResult {
 			let origin = ensure_signed(origin)?;
 			let dest = T::Lookup::lookup(dest)?;
 
 			Self::bare_call(origin, dest, value, gas_limit, data)
 				.map(|_| ())
-				.map_err(|e| e.reason)
+				.map_err(|e| e.reason.into())
 		}
 
 		/// Instantiates a new contract from the `codehash` generated by `put_code`, optionally transferring some balance.
@@ -611,7 +611,7 @@ decl_module! {
 			#[compact] gas_limit: Gas,
 			code_hash: CodeHash<T>,
 			data: Vec<u8>
-		) -> Result {
+		) -> DispatchResult {
 			let origin = ensure_signed(origin)?;
 
 			Self::execute_wasm(origin, gas_limit, |ctx, gas_meter| {
@@ -619,7 +619,7 @@ decl_module! {
 					.map(|(_address, output)| output)
 			})
 			.map(|_| ())
-			.map_err(|e| e.reason)
+			.map_err(|e| e.reason.into())
 		}
 
 		/// Allows block producers to claim a small reward for evicting a contract. If a block producer
@@ -636,10 +636,10 @@ decl_module! {
 				(Ok(frame_system::RawOrigin::None), Some(aux_sender)) => {
 					(false, aux_sender)
 				},
-				_ => return Err(
+				_ => Err(
 					"Invalid surcharge claim: origin must be signed or \
 					inherent and auxiliary sender only provided on inherent"
-				),
+				)?,
 			};
 
 			// Add some advantage for block producers (who send unsigned extrinsics) by
@@ -783,7 +783,7 @@ impl<T: Trait> Module<T> {
 		code_hash: CodeHash<T>,
 		rent_allowance: BalanceOf<T>,
 		delta: Vec<exec::StorageKey>
-	) -> Result {
+	) -> DispatchResult {
 		let mut origin_contract = <ContractInfoOf<T>>::get(&origin)
 			.and_then(|c| c.get_alive())
 			.ok_or("Cannot restore from inexisting or tombstone contract")?;
@@ -791,7 +791,7 @@ impl<T: Trait> Module<T> {
 		let current_block = <frame_system::Module<T>>::block_number();
 
 		if origin_contract.last_write == Some(current_block) {
-			return Err("Origin TrieId written in the current block");
+			Err("Origin TrieId written in the current block")?
 		}
 
 		let dest_tombstone = <ContractInfoOf<T>>::get(&dest)
@@ -816,7 +816,7 @@ impl<T: Trait> Module<T> {
 						origin_contract.child_trie_unique_id(),
 						&blake2_256(key),
 					);
-					
+
 					(key, value)
 				})
 			})
@@ -841,7 +841,7 @@ impl<T: Trait> Module<T> {
 				);
 			}
 
-			return Err("Tombstones don't match");
+			return Err("Tombstones don't match".into());
 		}
 
 		origin_contract.storage_size -= key_values_taken.iter()