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/support/test/tests/decl_error.rs

@@ -0,0 +1,135 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+#![recursion_limit="128"]
+
+use sp_runtime::{generic, traits::{BlakeTwo256, Block as _, Verify}, DispatchError};
+use sp_core::{H256, sr25519};
+
+mod system;
+
+pub trait Currency {}
+
+mod module1 {
+	use super::*;
+
+	pub trait Trait<I>: system::Trait {}
+
+	frame_support::decl_module! {
+		pub struct Module<T: Trait<I>, I: Instance = DefaultInstance> for enum Call
+			where origin: <T as system::Trait>::Origin
+		{
+			pub fn fail(_origin) -> frame_support::dispatch::DispatchResult {
+				Err(Error::<T, I>::Something.into())
+			}
+		}
+	}
+
+	frame_support::decl_error! {
+		pub enum Error for Module<T: Trait<I>, I: Instance> {
+			Something
+		}
+	}
+
+	frame_support::decl_storage! {
+		trait Store for Module<T: Trait<I>, I: Instance=DefaultInstance> as Module {}
+	}
+}
+
+mod module2 {
+	use super::*;
+
+	pub trait Trait: system::Trait {}
+
+	frame_support::decl_module! {
+		pub struct Module<T: Trait> for enum Call
+			where origin: <T as system::Trait>::Origin
+		{
+			pub fn fail(_origin) -> frame_support::dispatch::DispatchResult {
+				Err(Error::<T>::Something.into())
+			}
+		}
+	}
+
+	frame_support::decl_error! {
+		pub enum Error for Module<T: Trait> {
+			Something
+		}
+	}
+
+	frame_support::decl_storage! {
+		trait Store for Module<T: Trait> as Module {}
+	}
+}
+
+impl module1::Trait<module1::Instance1> for Runtime {}
+impl module1::Trait<module1::Instance2> for Runtime {}
+impl module2::Trait for Runtime {}
+
+pub type Signature = sr25519::Signature;
+pub type AccountId = <Signature as Verify>::Signer;
+pub type BlockNumber = u64;
+pub type Index = u64;
+
+impl system::Trait for Runtime {
+	type Hash = H256;
+	type Origin = Origin;
+	type BlockNumber = BlockNumber;
+	type AccountId = AccountId;
+	type Event = Event;
+	type ModuleToIndex = ModuleToIndex;
+}
+
+frame_support::construct_runtime!(
+	pub enum Runtime where
+		Block = Block,
+		NodeBlock = Block,
+		UncheckedExtrinsic = UncheckedExtrinsic
+	{
+		System: system::{Module, Call, Event},
+		Module1_1: module1::<Instance1>::{Module, Call, Storage},
+		Module2: module2::{Module, Call, Storage},
+		Module1_2: module1::<Instance2>::{Module, Call, Storage},
+	}
+);
+
+pub type Header = generic::Header<BlockNumber, BlakeTwo256>;
+pub type Block = generic::Block<Header, UncheckedExtrinsic>;
+pub type UncheckedExtrinsic = generic::UncheckedExtrinsic<u32, Call, Signature, ()>;
+
+#[test]
+fn check_module1_1_error_type() {
+	assert_eq!(
+		Module1_1::fail(system::Origin::<Runtime>::Root.into()),
+		Err(DispatchError::Module { index: 1, error: 0, message: Some("Something") }),
+	);
+}
+
+#[test]
+fn check_module1_2_error_type() {
+	assert_eq!(
+		Module1_2::fail(system::Origin::<Runtime>::Root.into()),
+		Err(DispatchError::Module { index: 3, error: 0, message: Some("Something") }),
+	);
+}
+
+#[test]
+fn check_module2_error_type() {
+	assert_eq!(
+		Module2::fail(system::Origin::<Runtime>::Root.into()),
+		Err(DispatchError::Module { index: 2, error: 0, message: Some("Something") }),
+	);
+}

substrate/frame/support/test/tests/instance.rs

@@ -238,6 +238,7 @@ impl system::Trait for Runtime {
 	type BlockNumber = BlockNumber;
 	type AccountId = AccountId;
 	type Event = Event;
+	type ModuleToIndex = ();
 }
 
 frame_support::construct_runtime!(

substrate/frame/support/test/tests/issue2219.rs

@@ -160,6 +160,7 @@ impl system::Trait for Runtime {
 	type BlockNumber = BlockNumber;
 	type AccountId = AccountId;
 	type Event = Event;
+	type ModuleToIndex = ();
 }
 
 impl module::Trait for Runtime {}

substrate/frame/support/test/tests/reserved_keyword/on_initialize.rs

@@ -12,14 +12,14 @@ macro_rules! reserved {
 				pub mod system {
 					use frame_support::dispatch;
 
-					pub fn ensure_root<R>(_: R) -> dispatch::Result {
+					pub fn ensure_root<R>(_: R) -> dispatch::DispatchResult {
 						Ok(())
 					}
 				}
 
 				frame_support::decl_module! {
 					pub struct Module<T: Trait> for enum Call where origin: T::Origin {
-						fn $reserved(_origin) -> dispatch::Result { unreachable!() }
+						fn $reserved(_origin) -> dispatch::DispatchResult { unreachable!() }
 					}
 				}
 			}

substrate/frame/support/test/tests/system.rs

@@ -8,6 +8,7 @@ pub trait Trait: 'static + Eq + Clone {
 	type Hash;
 	type AccountId: Encode + EncodeLike + Decode;
 	type Event: From<Event>;
+	type ModuleToIndex: frame_support::traits::ModuleToIndex;
 }
 
 frame_support::decl_module! {
@@ -28,7 +29,7 @@ frame_support::decl_event!(
 );
 
 frame_support::decl_error! {
-	pub enum Error {
+	pub enum Error for Module<T: Trait> {
 		/// Test error documentation
 		TestError,
 		/// Error documentation