Custom runtime module errors (#3433)

* srml-system checks

* wip

* more modules compiles

* node-runtime checks

* build.sh passes

* include dispatch error in failed event

* revert some unnecessary changes

* refactor based on comments

* more compile error fixes

* avoid unnecessary into

* reorder code

* fixes some tests

* manually implement encode & decode to avoid i8 workaround

* more test fixes

* more fixes

* more error fixes

* Apply suggestions from code review

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* address comments

* test for DispatchError encoding

* tyep alias for democracy

* make error printable

* line width

* fix balances tests

* fix executive test

* fix system tests

* bump version

* ensure consistent method signature

* Apply suggestions from code review

Co-Authored-By: Gavin Wood <github@gavwood.com>

* changes based on review

* Add issue number for TODOs

* fix

* line width

* fix test

* Update core/sr-primitives/src/lib.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update core/sr-primitives/src/traits.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update srml/council/src/motions.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update srml/council/src/motions.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* update based on review

* More concrete macro matching

* fix test build issue

* Update hex-literal dependency version. (#3141)

* Update hex-literal dep version.

* Update lock file.

* Start to rework the new error handling

* More work to get it back compiling

* Start to fix after master merge

* The great transaction error handling refactoring

* Make `decl_error` errors convertible to `&'static str`

* Make srml-executive build again

* Fix `sr-primitives` tests

* More fixes

* Last round of fix ups

* Fix build

* Fix build

* Apply suggestions from code review

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Rename some stuff

* Fixes after master merge

* Adds `CheckBlockGasLimit` signed extension

* Remove debug stuff

* Fix srml-balances test

* Rename `InvalidIndex` to `CannotLookup`

* Remove weird generic parameters

* Rename function again

* Fix import

* Document the signed extension

* Change from `Into` to `From`

* Update srml/contracts/src/lib.rs

Co-Authored-By: Sergei Pepyakin <sergei@parity.io>

* Fix compilation

* Update srml/contracts/src/lib.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Update core/sr-primitives/src/transaction_validity.rs

Co-Authored-By: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* Remove unused code

* Fix compilation

* Some cleanups

* Fix compile errors

* Make `TransactionValidity` a `Result`

* Apply suggestions from code review

Co-Authored-By: Gavin Wood <gavin@parity.io>

* Beautify the code a little bit and fix test

* Make `CannotLookup` an inherent error declared by `decl_error!`

* Adds some documentation

* Make `ApplyOutcome` a result

* Up the spec_version

* Apply suggestions from code review

Co-Authored-By: Gavin Wood <gavin@parity.io>
Co-Authored-By: DemiMarie-parity <48690212+DemiMarie-parity@users.noreply.github.com>

substrate/core/basic-authorship/src/basic_authorship.rs

@@ -30,9 +30,10 @@ use inherents::InherentData;
 use log::{error, info, debug, trace};
 use primitives::{H256, Blake2Hasher, ExecutionContext};
 use sr_primitives::{
-	traits::{Block as BlockT, Hash as HashT, Header as HeaderT, ProvideRuntimeApi, DigestFor, BlakeTwo256},
+	traits::{
+		Block as BlockT, Hash as HashT, Header as HeaderT, ProvideRuntimeApi, DigestFor, BlakeTwo256
+	},
 	generic::BlockId,
-	ApplyError,
 };
 use transaction_pool::txpool::{self, Pool as TransactionPool};
 use substrate_telemetry::{telemetry, CONSENSUS_INFO};
@@ -170,7 +171,7 @@ impl<Block, B, E, RA, A> Proposer<Block, SubstrateClient<B, E, Block, RA>, A>	wh
 				Ok(()) => {
 					debug!("[{:?}] Pushed to the block.", pending.hash);
 				}
-				Err(error::Error::ApplyExtrinsicFailed(ApplyError::FullBlock)) => {
+				Err(error::Error::ApplyExtrinsicFailed(e)) if e.exhausted_resources() => {
 					if is_first {
 						debug!("[{:?}] Invalid transaction: FullBlock on empty block", pending.hash);
 						unqueue_invalid.push(pending.hash.clone());
@@ -178,7 +179,7 @@ impl<Block, B, E, RA, A> Proposer<Block, SubstrateClient<B, E, Block, RA>, A>	wh
 						skipped += 1;
 						debug!(
 							"Block seems full, but will try {} more transactions before quitting.",
-							MAX_SKIPPED_TRANSACTIONS - skipped
+							MAX_SKIPPED_TRANSACTIONS - skipped,
 						);
 					} else {
 						debug!("Block is full, proceed with proposing.");

substrate/core/client/src/block_builder/block_builder.rs

@@ -17,7 +17,6 @@
 use super::api::BlockBuilder as BlockBuilderApi;
 use std::vec::Vec;
 use codec::Encode;
-use sr_primitives::ApplyOutcome;
 use sr_primitives::generic::BlockId;
 use sr_primitives::traits::{
 	Header as HeaderT, Hash, Block as BlockT, One, HashFor, ProvideRuntimeApi, ApiRef, DigestFor,
@@ -104,7 +103,7 @@ where
 				ExecutionContext::BlockConstruction,
 				xt.clone()
 			)? {
-				Ok(ApplyOutcome::Success) | Ok(ApplyOutcome::Fail) => {
+				Ok(_) => {
 					extrinsics.push(xt);
 					Ok(())
 				}

substrate/core/rpc/api/src/author/error.rs

@@ -101,15 +101,15 @@ impl From<Error> for rpc::Error {
 				message: format!("Verification Error: {}", e).into(),
 				data: Some(format!("{:?}", e).into()),
 			},
-			Error::Pool(PoolError::InvalidTransaction(code)) => rpc::Error {
+			Error::Pool(PoolError::InvalidTransaction(e)) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(POOL_INVALID_TX),
 				message: "Invalid Transaction".into(),
-				data: Some(code.into()),
+				data: serde_json::to_value(e).ok(),
 			},
-			Error::Pool(PoolError::UnknownTransactionValidity(code)) => rpc::Error {
+			Error::Pool(PoolError::UnknownTransaction(e)) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(POOL_UNKNOWN_VALIDITY),
 				message: "Unknown Transaction Validity".into(),
-				data: Some(code.into()),
+				data: serde_json::to_value(e).ok(),
 			},
 			Error::Pool(PoolError::TemporarilyBanned) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(POOL_TEMPORARILY_BANNED),
@@ -133,7 +133,7 @@ impl From<Error> for rpc::Error {
 			},
 			Error::Pool(PoolError::ImmediatelyDropped) => rpc::Error {
 				code: rpc::ErrorCode::ServerError(POOL_IMMEDIATELY_DROPPED),
-				message: "Immediately Dropped" .into(),
+				message: "Immediately Dropped".into(),
 				data: Some("The transaction couldn't enter the pool because of the limit".into()),
 			},
 			Error::UnsupportedKeyType => rpc::Error {

substrate/core/sr-io/src/lib.rs

@@ -55,7 +55,13 @@ pub mod offchain;
 /// Trait for things which can be printed.
 pub trait Printable {
 	/// Print the object.
-	fn print(self);
+	fn print(&self);
+}
+
+impl Printable for u8 {
+	fn print(&self) {
+		u64::from(*self).print()
+	}
 }
 
 /// Converts a public trait definition into a private trait and set of public functions

substrate/core/sr-io/with_std.rs

@@ -479,19 +479,19 @@ pub fn with_storage<R, F: FnOnce() -> R>(
 }
 
 impl<'a> Printable for &'a [u8] {
-	fn print(self) {
-		println!("Runtime: {}", HexDisplay::from(&self));
+	fn print(&self) {
+		println!("Runtime: {}", HexDisplay::from(self));
 	}
 }
 
 impl<'a> Printable for &'a str {
-	fn print(self) {
+	fn print(&self) {
 		println!("Runtime: {}", self);
 	}
 }
 
 impl Printable for u64 {
-	fn print(self) {
+	fn print(&self) {
 		println!("Runtime: {}", self);
 	}
 }

substrate/core/sr-io/without_std.rs

@@ -1220,7 +1220,7 @@ unsafe fn from_raw_parts(ptr: *mut u8, len: u32) -> Option<Vec<u8>> {
 impl Api for () {}
 
 impl<'a> Printable for &'a [u8] {
-	fn print(self) {
+	fn print(&self) {
 		unsafe {
 			ext_print_hex.get()(self.as_ptr(), self.len() as u32);
 		}
@@ -1228,7 +1228,7 @@ impl<'a> Printable for &'a [u8] {
 }
 
 impl<'a> Printable for &'a str {
-	fn print(self) {
+	fn print(&self) {
 		unsafe {
 			ext_print_utf8.get()(self.as_ptr() as *const u8, self.len() as u32);
 		}
@@ -1236,7 +1236,8 @@ impl<'a> Printable for &'a str {
 }
 
 impl Printable for u64 {
-	fn print(self) {
-		unsafe { ext_print_num.get()(self); }
+	fn print(&self) {
+		unsafe { ext_print_num.get()(*self); }
 	}
 }
+

substrate/core/sr-primitives/src/generic/checked_extrinsic.rs

@@ -17,10 +17,8 @@
 //! Generic implementation of an extrinsic that has passed the verification
 //! stage.
 
-use rstd::result::Result;
 use crate::traits::{
-	self, Member, MaybeDisplay, SignedExtension, DispatchError, Dispatchable, DispatchResult,
-	ValidateUnsigned
+	self, Member, MaybeDisplay, SignedExtension, Dispatchable, ValidateUnsigned,
 };
 use crate::weights::{GetDispatchInfo, DispatchInfo};
 use crate::transaction_validity::TransactionValidity;
@@ -55,28 +53,24 @@ where
 		self.signed.as_ref().map(|x| &x.0)
 	}
 
-	fn validate<U: ValidateUnsigned<Call=Self::Call>>(&self,
+	fn validate<U: ValidateUnsigned<Call = Self::Call>>(
+		&self,
 		info: DispatchInfo,
 		len: usize,
 	) -> TransactionValidity {
 		if let Some((ref id, ref extra)) = self.signed {
-			Extra::validate(extra, id, &self.function, info, len).into()
+			Extra::validate(extra, id, &self.function, info, len)
 		} else {
-			match Extra::validate_unsigned(&self.function, info, len) {
-				Ok(extra) => match U::validate_unsigned(&self.function) {
-					TransactionValidity::Valid(v) =>
-						TransactionValidity::Valid(v.combine_with(extra)),
-					x => x,
-				},
-				x => x.into(),
-			}
+			let valid = Extra::validate_unsigned(&self.function, info, len)?;
+			Ok(valid.combine_with(U::validate_unsigned(&self.function)?))
 		}
 	}
 
-	fn dispatch(self,
+	fn apply(
+		self,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<DispatchResult, DispatchError> {
+	) -> crate::ApplyResult {
 		let (maybe_who, pre) = if let Some((id, extra)) = self.signed {
 			let pre = Extra::pre_dispatch(extra, &id, &self.function, info, len)?;
 			(Some(id), pre)
@@ -86,7 +80,7 @@ where
 		};
 		let res = self.function.dispatch(Origin::from(maybe_who));
 		Extra::post_dispatch(pre, info, len);
-		Ok(res)
+		Ok(res.map_err(Into::into))
 	}
 }
 

substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs

@@ -21,9 +21,11 @@ use std::fmt;
 
 use rstd::prelude::*;
 use runtime_io::blake2_256;
-use crate::codec::{Decode, Encode, Input, Error};
-use crate::traits::{self, Member, MaybeDisplay, SignedExtension, Checkable, Extrinsic};
-use super::CheckedExtrinsic;
+use codec::{Decode, Encode, Input, Error};
+use crate::{
+	traits::{self, Member, MaybeDisplay, SignedExtension, Checkable, Extrinsic},
+	generic::CheckedExtrinsic, transaction_validity::{TransactionValidityError, InvalidTransaction},
+};
 
 const TRANSACTION_VERSION: u8 = 3;
 
@@ -101,11 +103,11 @@ where
 	Signature: Member + traits::Verify<Signer=AccountId>,
 	Extra: SignedExtension<AccountId=AccountId>,
 	AccountId: Member + MaybeDisplay,
-	Lookup: traits::Lookup<Source=Address, Target=AccountId>
+	Lookup: traits::Lookup<Source=Address, Target=AccountId>,
 {
 	type Checked = CheckedExtrinsic<AccountId, Call, Extra>;
 
-	fn check(self, lookup: &Lookup) -> Result<Self::Checked, &'static str> {
+	fn check(self, lookup: &Lookup) -> Result<Self::Checked, TransactionValidityError> {
 		Ok(match self.signature {
 			Some((signed, signature, extra)) => {
 				let signed = lookup.lookup(signed)?;
@@ -113,7 +115,7 @@ where
 				if !raw_payload.using_encoded(|payload| {
 					signature.verify(payload, &signed)
 				}) {
-					return Err(crate::BAD_SIGNATURE)
+					return Err(InvalidTransaction::BadProof.into())
 				}
 
 				let (function, extra, _) = raw_payload.deconstruct();
@@ -136,9 +138,9 @@ where
 /// is going to be different than the `SignaturePayload` - so the thing the extrinsic
 /// actually contains.
 pub struct SignedPayload<Call, Extra: SignedExtension>((
-		Call,
-		Extra,
-		Extra::AdditionalSigned,
+	Call,
+	Extra,
+	Extra::AdditionalSigned,
 ));
 
 impl<Call, Extra> SignedPayload<Call, Extra> where
@@ -148,7 +150,7 @@ impl<Call, Extra> SignedPayload<Call, Extra> where
 	/// Create new `SignedPayload`.
 	///
 	/// This function may fail if `additional_signed` of `Extra` is not available.
-	pub fn new(call: Call, extra: Extra) -> Result<Self, &'static str> {
+	pub fn new(call: Call, extra: Extra) -> Result<Self, TransactionValidityError> {
 		let additional_signed = extra.additional_signed()?;
 		let raw_payload = (call, extra, additional_signed);
 		Ok(Self(raw_payload))
@@ -256,7 +258,12 @@ where
 	Extra: SignedExtension,
 {
 	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		write!(f, "UncheckedExtrinsic({:?}, {:?})", self.signature.as_ref().map(|x| (&x.0, &x.2)), self.function)
+		write!(
+			f,
+			"UncheckedExtrinsic({:?}, {:?})",
+			self.signature.as_ref().map(|x| (&x.0, &x.2)),
+			self.function,
+		)
 	}
 }
 
@@ -265,15 +272,10 @@ mod tests {
 	use super::*;
 	use runtime_io::blake2_256;
 	use crate::codec::{Encode, Decode};
-	use crate::traits::{SignedExtension, Lookup};
+	use crate::traits::{SignedExtension, IdentityLookup};
 	use serde::{Serialize, Deserialize};
 
-	struct TestContext;
-	impl Lookup for TestContext {
-		type Source = u64;
-		type Target = u64;
-		fn lookup(&self, s: u64) -> Result<u64, &'static str> { Ok(s) }
-	}
+	type TestContext = IdentityLookup<u64>;
 
 	#[derive(Eq, PartialEq, Clone, Debug, Serialize, Deserialize, Encode, Decode)]
 	struct TestSig(u64, Vec<u8>);
@@ -298,7 +300,7 @@ mod tests {
 		type AdditionalSigned = ();
 		type Pre = ();
 
-		fn additional_signed(&self) -> rstd::result::Result<(), &'static str> { Ok(()) }
+		fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
 	}
 
 	type Ex = UncheckedExtrinsic<TestAccountId, TestCall, TestSig, TestExtra>;
@@ -340,7 +342,7 @@ mod tests {
 	fn unsigned_check_should_work() {
 		let ux = Ex::new_unsigned(vec![0u8; 0]);
 		assert!(!ux.is_signed().unwrap_or(false));
-		assert!(<Ex as Checkable<TestContext>>::check(ux, &TestContext).is_ok());
+		assert!(<Ex as Checkable<TestContext>>::check(ux, &Default::default()).is_ok());
 	}
 
 	#[test]
@@ -349,10 +351,13 @@ mod tests {
 			vec![0u8; 0],
 			TEST_ACCOUNT,
 			TestSig(TEST_ACCOUNT, vec![0u8; 0]),
-			TestExtra
+			TestExtra,
 		);
 		assert!(ux.is_signed().unwrap_or(false));
-		assert_eq!(<Ex as Checkable<TestContext>>::check(ux, &TestContext), Err(crate::BAD_SIGNATURE));
+		assert_eq!(
+			<Ex as Checkable<TestContext>>::check(ux, &Default::default()),
+			Err(InvalidTransaction::BadProof.into()),
+		);
 	}
 
 	#[test]
@@ -361,12 +366,12 @@ mod tests {
 			vec![0u8; 0],
 			TEST_ACCOUNT,
 			TestSig(TEST_ACCOUNT, (vec![0u8; 0], TestExtra).encode()),
-			TestExtra
+			TestExtra,
 		);
 		assert!(ux.is_signed().unwrap_or(false));
 		assert_eq!(
-			<Ex as Checkable<TestContext>>::check(ux, &TestContext),
-			Ok(CEx { signed: Some((TEST_ACCOUNT, TestExtra)), function: vec![0u8; 0] })
+			<Ex as Checkable<TestContext>>::check(ux, &Default::default()),
+			Ok(CEx { signed: Some((TEST_ACCOUNT, TestExtra)), function: vec![0u8; 0] }),
 		);
 	}
 

substrate/core/sr-primitives/src/lib.rs

@@ -58,19 +58,6 @@ pub use generic::{DigestItem, Digest};
 pub use primitives::crypto::{key_types, KeyTypeId, CryptoType};
 pub use app_crypto::AppKey;
 
-/// A message indicating an invalid signature in extrinsic.
-pub const BAD_SIGNATURE: &str = "bad signature in extrinsic";
-
-/// Full block error message.
-///
-/// This allows modules to indicate that given transaction is potentially valid
-/// in the future, but can't be executed in the current state.
-/// Note this error should be returned early in the execution to prevent DoS,
-/// cause the fees are not being paid if this error is returned.
-///
-/// Example: block gas limit is reached (the transaction can be retried in the next block though).
-pub const BLOCK_FULL: &str = "block size limit is reached";
-
 /// Justification type.
 pub type Justification = Vec<u8>;
 
@@ -636,53 +623,111 @@ impl From<ed25519::Signature> for AnySignature {
 	}
 }
 
-#[derive(Eq, PartialEq, Clone, Copy, Decode)]
+#[derive(Eq, PartialEq, Clone, Copy, Decode, Encode)]
 #[cfg_attr(feature = "std", derive(Debug, Serialize))]
-#[repr(u8)]
-/// Outcome of a valid extrinsic application. Capable of being sliced.
-pub enum ApplyOutcome {
-	/// Successful application (extrinsic reported no issue).
-	Success = 0,
-	/// Failed application (extrinsic was probably a no-op other than fees).
-	Fail = 1,
-}
-
-impl codec::Encode for ApplyOutcome {
-	fn using_encoded<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
-		f(&[*self as u8])
-	}
-}
-
-impl codec::EncodeLike for ApplyOutcome {}
-
-#[derive(Eq, PartialEq, Clone, Copy, Decode)]
-#[cfg_attr(feature = "std", derive(Debug, Serialize))]
-#[repr(u8)]
 /// Reason why an extrinsic couldn't be applied (i.e. invalid extrinsic).
 pub enum ApplyError {
-	/// Bad signature.
-	BadSignature = 0,
-	/// Nonce too low.
-	Stale = 1,
-	/// Nonce too high.
-	Future = 2,
-	/// Sending account had too low a balance.
-	CantPay = 3,
-	/// Block is full, no more extrinsics can be applied.
-	FullBlock = 255,
+	/// General error to do with the permissions of the sender.
+	NoPermission,
+
+	/// General error to do with the state of the system in general.
+	BadState,
+
+	/// Any error to do with the transaction validity.
+	Validity(transaction_validity::TransactionValidityError),
 }
 
-impl codec::Encode for ApplyError {
-	fn using_encoded<R, F: FnOnce(&[u8]) -> R>(&self, f: F) -> R {
-		f(&[*self as u8])
+impl ApplyError {
+	/// Returns if the reason for the error was block resource exhaustion.
+	pub fn exhausted_resources(&self) -> bool {
+		match self {
+			Self::Validity(e) => e.exhausted_resources(),
+			_ => false,
+		}
 	}
 }
 
-impl codec::EncodeLike for ApplyError {}
+impl From<ApplyError> for &'static str {
+	fn from(err: ApplyError) -> &'static str {
+		match err {
+			ApplyError::NoPermission => "Transaction does not have required permissions",
+			ApplyError::BadState => "System state currently prevents this transaction",
+			ApplyError::Validity(v) => v.into(),
+		}
+	}
+}
+
+impl From<transaction_validity::TransactionValidityError> for ApplyError {
+	fn from(err: transaction_validity::TransactionValidityError) -> Self {
+		ApplyError::Validity(err)
+	}
+}
+
+/// The outcome of applying a transaction.
+pub type ApplyOutcome = Result<(), DispatchError>;
+
+impl From<DispatchError> for ApplyOutcome {
+	fn from(err: DispatchError) -> Self {
+		Err(err)
+	}
+}
 
 /// Result from attempt to apply an extrinsic.
 pub type ApplyResult = Result<ApplyOutcome, ApplyError>;
 
+#[derive(Eq, PartialEq, Clone, Copy, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug, Serialize))]
+/// Reason why a dispatch call failed
+pub struct DispatchError {
+	/// Module index, matching the metadata module index
+	pub module: Option<u8>,
+	/// Module specific error value
+	pub error: u8,
+	/// Optional error message.
+	#[codec(skip)]
+	pub message: Option<&'static str>,
+}
+
+impl DispatchError {
+	/// Create a new instance of `DispatchError`.
+	pub fn new(module: Option<u8>, error: u8, message: Option<&'static str>) -> Self {
+		Self {
+			module,
+			error,
+			message,
+		}
+	}
+}
+
+impl runtime_io::Printable for DispatchError {
+	fn print(&self) {
+		"DispatchError".print();
+		if let Some(module) = self.module {
+			module.print();
+		}
+		self.error.print();
+		if let Some(msg) = self.message {
+			msg.print();
+		}
+	}
+}
+
+impl traits::ModuleDispatchError for &'static str {
+	fn as_u8(&self) -> u8 {
+		0
+	}
+
+	fn as_str(&self) -> &'static str {
+		self
+	}
+}
+
+impl From<&'static str> for DispatchError {
+	fn from(err: &'static str) -> DispatchError {
+		DispatchError::new(None, 0, Some(err))
+	}
+}
+
 /// Verify a signature on an encoded value in a lazy manner. This can be
 /// an optimization if the signature scheme has an "unsigned" escape hash.
 pub fn verify_encoded_lazy<V: Verify, T: codec::Encode>(sig: &V, item: &T, signer: &V::Signer) -> bool {
@@ -852,6 +897,7 @@ impl traits::Extrinsic for OpaqueExtrinsic {
 
 #[cfg(test)]
 mod tests {
+	use super::DispatchError;
 	use crate::codec::{Encode, Decode};
 	use super::{Perbill, Permill};
 
@@ -967,6 +1013,26 @@ mod tests {
 		);
 	}
 
+	#[test]
+	fn dispatch_error_encoding() {
+		let error = DispatchError {
+			module: Some(1),
+			error: 2,
+			message: Some("error message"),
+		};
+		let encoded = error.encode();
+		let decoded = DispatchError::decode(&mut &encoded[..]).unwrap();
+		assert_eq!(encoded, vec![1, 1, 2]);
+		assert_eq!(
+			decoded,
+			DispatchError {
+				module: Some(1),
+				error: 2,
+				message: None,
+			},
+		);
+	}
+
 	#[test]
 	fn per_bill_square() {
 		const FIXTURES: &[(u32, u32)] = &[

substrate/core/sr-primitives/src/testing.rs

@@ -20,14 +20,14 @@ use serde::{Serialize, Serializer, Deserialize, de::Error as DeError, Deserializ
 use std::{fmt::Debug, ops::Deref, fmt};
 use crate::codec::{Codec, Encode, Decode};
 use crate::traits::{
-	self, Checkable, Applyable, BlakeTwo256, OpaqueKeys, DispatchError, DispatchResult,
-	ValidateUnsigned, SignedExtension, Dispatchable,
+	self, Checkable, Applyable, BlakeTwo256, OpaqueKeys, ValidateUnsigned,
+	SignedExtension, Dispatchable,
 };
-use crate::{generic, KeyTypeId};
+use crate::{generic, KeyTypeId, ApplyResult};
 use crate::weights::{GetDispatchInfo, DispatchInfo};
 pub use primitives::H256;
 use primitives::{crypto::{CryptoType, Dummy, key_types, Public}, U256};
-use crate::transaction_validity::TransactionValidity;
+use crate::transaction_validity::{TransactionValidity, TransactionValidityError};
 
 /// Authority Id
 #[derive(Default, PartialEq, Eq, Clone, Encode, Decode, Debug, Hash, Serialize, Deserialize)]
@@ -271,7 +271,7 @@ impl<Call, Extra> Debug for TestXt<Call, Extra> {
 
 impl<Call: Codec + Sync + Send, Context, Extra> Checkable<Context> for TestXt<Call, Extra> {
 	type Checked = Self;
-	fn check(self, _: &Context) -> Result<Self::Checked, &'static str> { Ok(self) }
+	fn check(self, _: &Context) -> Result<Self::Checked, TransactionValidityError> { Ok(self) }
 }
 impl<Call: Codec + Sync + Send, Extra> traits::Extrinsic for TestXt<Call, Extra> {
 	type Call = Call;
@@ -289,7 +289,7 @@ impl<Call: Codec + Sync + Send, Extra> traits::Extrinsic for TestXt<Call, Extra>
 impl<Origin, Call, Extra> Applyable for TestXt<Call, Extra> where
 	Call: 'static + Sized + Send + Sync + Clone + Eq + Codec + Debug + Dispatchable<Origin=Origin>,
 	Extra: SignedExtension<AccountId=u64, Call=Call>,
-	Origin: From<Option<u64>>
+	Origin: From<Option<u64>>,
 {
 	type AccountId = u64;
 	type Call = Call;
@@ -297,19 +297,21 @@ impl<Origin, Call, Extra> Applyable for TestXt<Call, Extra> where
 	fn sender(&self) -> Option<&Self::AccountId> { self.0.as_ref().map(|x| &x.0) }
 
 	/// Checks to see if this is a valid *transaction*. It returns information on it if so.
-	fn validate<U: ValidateUnsigned<Call=Self::Call>>(&self,
+	fn validate<U: ValidateUnsigned<Call=Self::Call>>(
+		&self,
 		_info: DispatchInfo,
 		_len: usize,
 	) -> TransactionValidity {
-		TransactionValidity::Valid(Default::default())
+		Ok(Default::default())
 	}
 
 	/// Executes all necessary logic needed prior to dispatch and deconstructs into function call,
 	/// index and sender.
-	fn dispatch(self,
+	fn apply(
+		self,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<DispatchResult, DispatchError> {
+	) -> ApplyResult {
 		let maybe_who = if let Some((who, extra)) = self.0 {
 			Extra::pre_dispatch(extra, &who, &self.1, info, len)?;
 			Some(who)
@@ -317,7 +319,8 @@ impl<Origin, Call, Extra> Applyable for TestXt<Call, Extra> where
 			Extra::pre_dispatch_unsigned(&self.1, info, len)?;
 			None
 		};
-		Ok(self.1.dispatch(maybe_who.into()))
+
+		Ok(self.1.dispatch(maybe_who.into()).map_err(Into::into))
 	}
 }
 

substrate/core/sr-primitives/src/traits.rs

@@ -23,7 +23,9 @@ use runtime_io;
 #[cfg(feature = "std")] use serde::{Serialize, Deserialize, de::DeserializeOwned};
 use primitives::{self, Hasher, Blake2Hasher};
 use crate::codec::{Codec, Encode, Decode, HasCompact};
-use crate::transaction_validity::{ValidTransaction, TransactionValidity};
+use crate::transaction_validity::{
+	ValidTransaction, TransactionValidity, TransactionValidityError, UnknownTransaction,
+};
 use crate::generic::{Digest, DigestItem};
 use crate::weights::DispatchInfo;
 pub use integer_sqrt::IntegerSquareRoot;
@@ -93,18 +95,44 @@ impl<
 	}
 }
 
+/// An error type that indicates that the origin is invalid.
+#[derive(Encode, Decode)]
+pub struct InvalidOrigin;
+
+impl From<InvalidOrigin> for &'static str {
+	fn from(_: InvalidOrigin) -> &'static str {
+		"Invalid origin"
+	}
+}
+
 /// Some sort of check on the origin is performed by this object.
 pub trait EnsureOrigin<OuterOrigin> {
 	/// A return type.
 	type Success;
 	/// Perform the origin check.
-	fn ensure_origin(o: OuterOrigin) -> result::Result<Self::Success, &'static str> {
-		Self::try_origin(o).map_err(|_| "Invalid origin")
+	fn ensure_origin(o: OuterOrigin) -> result::Result<Self::Success, InvalidOrigin> {
+		Self::try_origin(o).map_err(|_| InvalidOrigin)
 	}
 	/// Perform the origin check.
 	fn try_origin(o: OuterOrigin) -> result::Result<Self::Success, OuterOrigin>;
 }
 
+/// An error that indicates that a lookup failed.
+#[derive(Encode, Decode)]
+pub struct LookupError;
+
+impl From<LookupError> for &'static str {
+	fn from(_: LookupError) -> &'static str {
+		"Can not lookup"
+	}
+}
+
+impl From<LookupError> for TransactionValidityError {
+	fn from(_: LookupError) -> Self {
+		UnknownTransaction::CannotLookup.into()
+	}
+}
+
 /// Means of changing one type into another in a manner dependent on the source type.
 pub trait Lookup {
 	/// Type to lookup from.
@@ -112,7 +140,7 @@ pub trait Lookup {
 	/// Type to lookup into.
 	type Target;
 	/// Attempt a lookup.
-	fn lookup(&self, s: Self::Source) -> result::Result<Self::Target, &'static str>;
+	fn lookup(&self, s: Self::Source) -> Result<Self::Target, LookupError>;
 }
 
 /// Means of changing one type into another in a manner dependent on the source type.
@@ -124,7 +152,7 @@ pub trait StaticLookup {
 	/// Type to lookup into.
 	type Target;
 	/// Attempt a lookup.
-	fn lookup(s: Self::Source) -> result::Result<Self::Target, &'static str>;
+	fn lookup(s: Self::Source) -> Result<Self::Target, LookupError>;
 	/// Convert from Target back to Source.
 	fn unlookup(t: Self::Target) -> Self::Source;
 }
@@ -135,13 +163,14 @@ pub struct IdentityLookup<T>(PhantomData<T>);
 impl<T: Codec + Clone + PartialEq + MaybeDebug> StaticLookup for IdentityLookup<T> {
 	type Source = T;
 	type Target = T;
-	fn lookup(x: T) -> result::Result<T, &'static str> { Ok(x) }
+	fn lookup(x: T) -> Result<T, LookupError> { Ok(x) }
 	fn unlookup(x: T) -> T { x }
 }
+
 impl<T> Lookup for IdentityLookup<T> {
 	type Source = T;
 	type Target = T;
-	fn lookup(&self, x: T) -> result::Result<T, &'static str> { Ok(x) }
+	fn lookup(&self, x: T) -> Result<T, LookupError> { Ok(x) }
 }
 
 /// Extensible conversion trait. Generic over both source and destination types.
@@ -781,7 +810,7 @@ pub trait Checkable<Context>: Sized {
 	type Checked;
 
 	/// Check self, given an instance of Context.
-	fn check(self, c: &Context) -> Result<Self::Checked, &'static str>;
+	fn check(self, c: &Context) -> Result<Self::Checked, TransactionValidityError>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
@@ -793,61 +822,21 @@ pub trait BlindCheckable: Sized {
 	type Checked;
 
 	/// Check self.
-	fn check(self) -> Result<Self::Checked, &'static str>;
+	fn check(self) -> Result<Self::Checked, TransactionValidityError>;
 }
 
 // Every `BlindCheckable` is also a `StaticCheckable` for arbitrary `Context`.
 impl<T: BlindCheckable, Context> Checkable<Context> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
-	fn check(self, _c: &Context) -> Result<Self::Checked, &'static str> {
+
+	fn check(self, _c: &Context) -> Result<Self::Checked, TransactionValidityError> {
 		BlindCheckable::check(self)
 	}
 }
 
-/// An abstract error concerning an attempt to verify, check or dispatch the transaction. This
-/// cannot be more concrete because it's designed to work reasonably well over a broad range of
-/// possible transaction types.
-#[cfg_attr(feature = "std", derive(PartialEq, Debug))]
-pub enum DispatchError {
-	/// General error to do with the inability to pay some fees (e.g. account balance too low).
-	Payment,
-
-	/// General error to do with the exhaustion of block resources.
-	Exhausted,
-
-	/// General error to do with the permissions of the sender.
-	NoPermission,
-
-	/// General error to do with the state of the system in general.
-	BadState,
-
-	/// General error to do with the transaction being outdated (e.g. nonce too low).
-	Stale,
-
-	/// General error to do with the transaction not yet being valid (e.g. nonce too high).
-	Future,
-
-	/// General error to do with the transaction's proofs (e.g. signature).
-	BadProof,
-}
-
-impl From<DispatchError> for i8 {
-	fn from(e: DispatchError) -> i8 {
-		match e {
-			DispatchError::Payment => -64,
-			DispatchError::Exhausted => -65,
-			DispatchError::NoPermission => -66,
-			DispatchError::BadState => -67,
-			DispatchError::Stale => -68,
-			DispatchError::Future => -69,
-			DispatchError::BadProof => -70,
-		}
-	}
-}
-
 /// Result of a module function call; either nothing (functions are only called for "side effects")
 /// or an error message.
-pub type DispatchResult = result::Result<(), &'static str>;
+pub type DispatchResult<Error> = result::Result<(), Error>;
 
 /// A lazy call (module function and argument values) that can be executed via its `dispatch`
 /// method.
@@ -858,15 +847,15 @@ pub trait Dispatchable {
 	type Origin;
 	/// ...
 	type Trait;
+	/// The error type returned by this dispatchable.
+	type Error: Into<crate::DispatchError>;
 	/// Actually dispatch this call and result the result of it.
-	fn dispatch(self, origin: Self::Origin) -> DispatchResult;
+	fn dispatch(self, origin: Self::Origin) -> DispatchResult<Self::Error>;
 }
 
 /// Means by which a transaction may be extended. This type embodies both the data and the logic
 /// that should be additionally associated with the transaction. It should be plain old data.
-pub trait SignedExtension:
-	Codec + MaybeDebug + Sync + Send + Clone + Eq + PartialEq
-{
+pub trait SignedExtension: Codec + MaybeDebug + Sync + Send + Clone + Eq + PartialEq {
 	/// The type which encodes the sender identity.
 	type AccountId;
 
@@ -882,7 +871,7 @@ pub trait SignedExtension:
 
 	/// Construct any additional data that should be in the signed payload of the transaction. Can
 	/// also perform any pre-signature-verification checks and return an error if needed.
-	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str>;
+	fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError>;
 
 	/// Validate a signed transaction for the transaction queue.
 	///
@@ -899,8 +888,8 @@ pub trait SignedExtension:
 		_call: &Self::Call,
 		_info: DispatchInfo,
 		_len: usize,
-	) -> Result<ValidTransaction, DispatchError> {
-		Ok(Default::default())
+	) -> TransactionValidity {
+		Ok(ValidTransaction::default())
 	}
 
 	/// Do any pre-flight stuff for a signed transaction.
@@ -917,8 +906,10 @@ pub trait SignedExtension:
 		call: &Self::Call,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<Self::Pre, DispatchError> {
-		self.validate(who, call, info, len).map(|_| Self::Pre::default())
+	) -> Result<Self::Pre, crate::ApplyError> {
+		self.validate(who, call, info, len)
+			.map(|_| Self::Pre::default())
+			.map_err(Into::into)
 	}
 
 	/// Validate an unsigned transaction for the transaction queue.
@@ -936,7 +927,9 @@ pub trait SignedExtension:
 		_call: &Self::Call,
 		_info: DispatchInfo,
 		_len: usize,
-	) -> Result<ValidTransaction, DispatchError> { Ok(Default::default()) }
+	) -> TransactionValidity {
+		Ok(ValidTransaction::default())
+	}
 
 	/// Do any pre-flight stuff for a unsigned transaction.
 	///
@@ -950,16 +943,25 @@ pub trait SignedExtension:
 		call: &Self::Call,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<Self::Pre, DispatchError> {
-		Self::validate_unsigned(call, info, len).map(|_| Self::Pre::default())
+	) -> Result<Self::Pre, crate::ApplyError> {
+		Self::validate_unsigned(call, info, len)
+			.map(|_| Self::Pre::default())
+			.map_err(Into::into)
 	}
 
 	/// Do any post-flight stuff for a transaction.
-	fn post_dispatch(
-		_pre: Self::Pre,
-		_info: DispatchInfo,
-		_len: usize,
-	) { }
+	fn post_dispatch(_pre: Self::Pre, _info: DispatchInfo, _len: usize) { }
+}
+
+/// An error that is returned by a dispatchable function of a module.
+pub trait ModuleDispatchError {
+	/// Convert this error to an `u8`.
+	///
+	/// The `u8` corresponds to the index of the variant in the error enum.
+	fn as_u8(&self) -> u8;
+
+	/// Convert the error to a `&'static str`.
+	fn as_str(&self) -> &'static str;
 }
 
 macro_rules! tuple_impl_indexed {
@@ -974,10 +976,10 @@ macro_rules! tuple_impl_indexed {
 		> SignedExtension for ($($direct),+,) {
 			type AccountId = AccountId;
 			type Call = Call;
-			type AdditionalSigned = ($($direct::AdditionalSigned,)+);
+			type AdditionalSigned = ( $( $direct::AdditionalSigned, )+ );
 			type Pre =  ($($direct::Pre,)+);
-			fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
-				Ok(( $(self.$index.additional_signed()?,)+ ))
+			fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError> {
+				Ok(( $( self.$index.additional_signed()?, )+ ))
 			}
 			fn validate(
 				&self,
@@ -985,9 +987,16 @@ macro_rules! tuple_impl_indexed {
 				call: &Self::Call,
 				info: DispatchInfo,
 				len: usize,
-			) -> Result<ValidTransaction, DispatchError> {
-				let aggregator = vec![$(<$direct as SignedExtension>::validate(&self.$index, who, call, info, len)?),+];
-				Ok(aggregator.into_iter().fold(ValidTransaction::default(), |acc, a| acc.combine_with(a)))
+			) -> TransactionValidity {
+				let aggregator = vec![
+					$( <$direct as SignedExtension>::validate(&self.$index, who, call, info, len)? ),+
+				];
+				Ok(
+					aggregator.into_iter().fold(
+						ValidTransaction::default(),
+						|acc, a| acc.combine_with(a),
+					)
+				)
 			}
 			fn pre_dispatch(
 				self,
@@ -995,22 +1004,28 @@ macro_rules! tuple_impl_indexed {
 				call: &Self::Call,
 				info: DispatchInfo,
 				len: usize,
-			) -> Result<Self::Pre, DispatchError> {
+			) -> Result<Self::Pre, $crate::ApplyError> {
 				Ok(($(self.$index.pre_dispatch(who, call, info, len)?,)+))
 			}
 			fn validate_unsigned(
 				call: &Self::Call,
 				info: DispatchInfo,
 				len: usize,
-			) -> Result<ValidTransaction, DispatchError> {
-				let aggregator = vec![$($direct::validate_unsigned(call, info, len)?),+];
-				Ok(aggregator.into_iter().fold(ValidTransaction::default(), |acc, a| acc.combine_with(a)))
+			) -> TransactionValidity {
+				let aggregator = vec![ $( $direct::validate_unsigned(call, info, len)? ),+ ];
+
+				Ok(
+					aggregator.into_iter().fold(
+						ValidTransaction::default(),
+						|acc, a| acc.combine_with(a),
+					)
+				)
 			}
 			fn pre_dispatch_unsigned(
 				call: &Self::Call,
 				info: DispatchInfo,
 				len: usize,
-			) -> Result<Self::Pre, DispatchError> {
+			) -> Result<Self::Pre, $crate::ApplyError> {
 				Ok(($($direct::pre_dispatch_unsigned(call, info, len)?,)+))
 			}
 			fn post_dispatch(
@@ -1047,7 +1062,7 @@ impl SignedExtension for () {
 	type AdditionalSigned = ();
 	type Call = ();
 	type Pre = ();
-	fn additional_signed(&self) -> rstd::result::Result<(), &'static str> { Ok(()) }
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
 }
 
 /// An "executable" piece of information, used by the standard Substrate Executive in order to
@@ -1067,17 +1082,19 @@ pub trait Applyable: Sized + Send + Sync {
 	fn sender(&self) -> Option<&Self::AccountId>;
 
 	/// Checks to see if this is a valid *transaction*. It returns information on it if so.
-	fn validate<V: ValidateUnsigned<Call=Self::Call>>(&self,
+	fn validate<V: ValidateUnsigned<Call=Self::Call>>(
+		&self,
 		info: DispatchInfo,
 		len: usize,
 	) -> TransactionValidity;
 
 	/// Executes all necessary logic needed prior to dispatch and deconstructs into function call,
 	/// index and sender.
-	fn dispatch(self,
+	fn apply(
+		self,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<DispatchResult, DispatchError>;
+	) -> crate::ApplyResult;
 }
 
 /// Auxiliary wrapper that holds an api instance and binds it to the given lifetime.

substrate/core/sr-primitives/src/transaction_validity.rs

@@ -17,8 +17,7 @@
 //! Transaction validity interface.
 
 use rstd::prelude::*;
-use crate::codec::{Encode, Decode, Error};
-use crate::traits::DispatchError;
+use crate::codec::{Encode, Decode};
 
 /// Priority for a transaction. Additive. Higher is better.
 pub type TransactionPriority = u64;
@@ -30,29 +29,151 @@ pub type TransactionLongevity = u64;
 /// Tag for a transaction. No two transactions with the same tag should be placed on-chain.
 pub type TransactionTag = Vec<u8>;
 
-/// Information on a transaction's validity and, if valid, on how it relates to other transactions.
-#[derive(Clone, PartialEq, Eq, Encode)]
-#[cfg_attr(feature = "std", derive(Debug))]
-pub enum TransactionValidity {
-	/// Transaction is invalid. Details are described by the error code.
-	Invalid(i8),
-	/// Transaction is valid.
-	Valid(ValidTransaction),
-	/// Transaction validity can't be determined.
-	Unknown(i8),
+/// An invalid transaction validity.
+#[derive(Clone, PartialEq, Eq, Encode, Decode, Copy)]
+#[cfg_attr(feature = "std", derive(Debug, serde::Serialize))]
+pub enum InvalidTransaction {
+	/// The call of the transaction is not expected.
+	Call,
+	/// General error to do with the inability to pay some fees (e.g. account balance too low).
+	Payment,
+	/// General error to do with the transaction not yet being valid (e.g. nonce too high).
+	Future,
+	/// General error to do with the transaction being outdated (e.g. nonce too low).
+	Stale,
+	/// General error to do with the transaction's proofs (e.g. signature).
+	BadProof,
+	/// The transaction birth block is ancient.
+	AncientBirthBlock,
+	/// The transaction would exhaust the resources of current block.
+	///
+	/// The transaction might be valid, but there are not enough resources left in the current block.
+	ExhaustsResources,
+	/// Any other custom invalid validity that is not covered by this enum.
+	Custom(u8),
 }
 
-impl From<Result<ValidTransaction, DispatchError>> for TransactionValidity {
-	fn from(r: Result<ValidTransaction, DispatchError>) -> Self {
-		match r {
-			Ok(v) => TransactionValidity::Valid(v),
-			Err(e) => TransactionValidity::Invalid(e.into()),
+impl InvalidTransaction {
+	/// Returns if the reason for the invalidity was block resource exhaustion.
+	pub fn exhausted_resources(&self) -> bool {
+		match self {
+			Self::ExhaustsResources => true,
+			_ => false,
 		}
 	}
 }
 
+impl From<InvalidTransaction> for &'static str {
+	fn from(invalid: InvalidTransaction) -> &'static str {
+		match invalid {
+			InvalidTransaction::Call => "Transaction call is not expected",
+			InvalidTransaction::Future => "Transaction will be valid in the future",
+			InvalidTransaction::Stale => "Transaction is outdated",
+			InvalidTransaction::BadProof => "Transaction has a bad signature",
+			InvalidTransaction::AncientBirthBlock => "Transaction has an ancient birth block",
+			InvalidTransaction::ExhaustsResources =>
+				"Transaction would exhausts the block limits",
+			InvalidTransaction::Payment =>
+				"Inability to pay some fees (e.g. account balance too low)",
+			InvalidTransaction::Custom(_) => "InvalidTransaction custom error",
+		}
+	}
+}
+
+/// An unknown transaction validity.
+#[derive(Clone, PartialEq, Eq, Encode, Decode, Copy)]
+#[cfg_attr(feature = "std", derive(Debug, serde::Serialize))]
+pub enum UnknownTransaction {
+	/// Could not lookup some information that is required to validate the transaction.
+	CannotLookup,
+	/// No validator found for the given unsigned transaction.
+	NoUnsignedValidator,
+	/// Any other custom unknown validity that is not covered by this enum.
+	Custom(u8),
+}
+
+impl From<UnknownTransaction> for &'static str {
+	fn from(unknown: UnknownTransaction) -> &'static str {
+		match unknown {
+			UnknownTransaction::CannotLookup =>
+				"Could not lookup information required to validate the transaction",
+			UnknownTransaction::NoUnsignedValidator =>
+				"Could not find an unsigned validator for the unsigned transaction",
+			UnknownTransaction::Custom(_) => "UnknownTransaction custom error",
+		}
+	}
+}
+
+/// Errors that can occur while checking the validity of a transaction.
+#[derive(Clone, PartialEq, Eq, Encode, Decode, Copy)]
+#[cfg_attr(feature = "std", derive(Debug, serde::Serialize))]
+pub enum TransactionValidityError {
+	/// The transaction is invalid.
+	Invalid(InvalidTransaction),
+	/// Transaction validity can't be determined.
+	Unknown(UnknownTransaction),
+}
+
+impl TransactionValidityError {
+	/// Returns `true` if the reason for the error was block resource exhaustion.
+	pub fn exhausted_resources(&self) -> bool {
+		match self {
+			Self::Invalid(e) => e.exhausted_resources(),
+			Self::Unknown(_) => false,
+		}
+	}
+}
+
+impl From<TransactionValidityError> for &'static str {
+	fn from(err: TransactionValidityError) -> &'static str {
+		match err {
+			TransactionValidityError::Invalid(invalid) => invalid.into(),
+			TransactionValidityError::Unknown(unknown) => unknown.into(),
+		}
+	}
+}
+
+impl From<InvalidTransaction> for TransactionValidityError {
+	fn from(err: InvalidTransaction) -> Self {
+		TransactionValidityError::Invalid(err)
+	}
+}
+
+impl From<UnknownTransaction> for TransactionValidityError {
+	fn from(err: UnknownTransaction) -> Self {
+		TransactionValidityError::Unknown(err)
+	}
+}
+
+impl From<InvalidTransaction> for crate::ApplyError {
+	fn from(invalid: InvalidTransaction) -> crate::ApplyError {
+		TransactionValidityError::from(invalid).into()
+	}
+}
+
+impl From<UnknownTransaction> for crate::ApplyError {
+	fn from(unknown: UnknownTransaction) -> crate::ApplyError {
+		TransactionValidityError::from(unknown).into()
+	}
+}
+
+/// Information on a transaction's validity and, if valid, on how it relates to other transactions.
+pub type TransactionValidity = Result<ValidTransaction, TransactionValidityError>;
+
+impl Into<TransactionValidity> for InvalidTransaction {
+	fn into(self) -> TransactionValidity {
+		Err(self.into())
+	}
+}
+
+impl Into<TransactionValidity> for UnknownTransaction {
+	fn into(self) -> TransactionValidity {
+		Err(self.into())
+	}
+}
+
 /// Information concerning a valid transaction.
-#[derive(Clone, PartialEq, Eq, Encode)]
+#[derive(Clone, PartialEq, Eq, Encode, Decode)]
 #[cfg_attr(feature = "std", derive(Debug))]
 pub struct ValidTransaction {
 	/// Priority of the transaction.
@@ -112,49 +233,13 @@ impl ValidTransaction {
 	}
 }
 
-impl Decode for TransactionValidity {
-	fn decode<I: crate::codec::Input>(value: &mut I) -> Result<Self, Error> {
-		match value.read_byte()? {
-			0 => Ok(TransactionValidity::Invalid(i8::decode(value)?)),
-			1 => {
-				let priority = TransactionPriority::decode(value)?;
-				let requires = Vec::decode(value)?;
-				let provides = Vec::decode(value)?;
-				let longevity = TransactionLongevity::decode(value)?;
-				let propagate = bool::decode(value).unwrap_or(true);
-
-				Ok(TransactionValidity::Valid(ValidTransaction {
-					priority, requires, provides, longevity, propagate,
-				}))
-			},
-			2 => Ok(TransactionValidity::Unknown(i8::decode(value)?)),
-			_ => Err("Invalid transaction validity variant".into()),
-		}
-	}
-}
-
 #[cfg(test)]
 mod tests {
 	use super::*;
 
-	#[test]
-	fn should_decode_with_backward_compat() {
-		let old_encoding = vec![
-			1, 5, 0, 0, 0, 0, 0, 0, 0, 4, 16, 1, 2, 3, 4, 4, 12, 4, 5, 6, 42, 0, 0, 0, 0, 0, 0, 0
-		];
-
-		assert_eq!(TransactionValidity::decode(&mut &*old_encoding), Ok(TransactionValidity::Valid(ValidTransaction {
-			priority: 5,
-			requires: vec![vec![1, 2, 3, 4]],
-			provides: vec![vec![4, 5, 6]],
-			longevity: 42,
-			propagate: true,
-		})));
-	}
-
 	#[test]
 	fn should_encode_and_decode() {
-		let v = TransactionValidity::Valid(ValidTransaction {
+		let v: TransactionValidity = Ok(ValidTransaction {
 			priority: 5,
 			requires: vec![vec![1, 2, 3, 4]],
 			provides: vec![vec![4, 5, 6]],
@@ -165,7 +250,7 @@ mod tests {
 		let encoded = v.encode();
 		assert_eq!(
 			encoded,
-			vec![1, 5, 0, 0, 0, 0, 0, 0, 0, 4, 16, 1, 2, 3, 4, 4, 12, 4, 5, 6, 42, 0, 0, 0, 0, 0, 0, 0, 0]
+			vec![0, 5, 0, 0, 0, 0, 0, 0, 0, 4, 16, 1, 2, 3, 4, 4, 12, 4, 5, 6, 42, 0, 0, 0, 0, 0, 0, 0, 0]
 		);
 
 		// decode back

substrate/core/test-runtime/src/lib.rs

@@ -38,7 +38,9 @@ use substrate_client::{
 };
 use sr_primitives::{
 	ApplyResult, create_runtime_str, Perbill, impl_opaque_keys,
-	transaction_validity::{TransactionValidity, ValidTransaction},
+	transaction_validity::{
+		TransactionValidity, ValidTransaction, TransactionValidityError, InvalidTransaction,
+	},
 	traits::{
 		BlindCheckable, BlakeTwo256, Block as BlockT, Extrinsic as ExtrinsicT,
 		GetNodeBlockType, GetRuntimeBlockType, Verify, IdentityLookup,
@@ -123,17 +125,17 @@ impl serde::Serialize for Extrinsic {
 impl BlindCheckable for Extrinsic {
 	type Checked = Self;
 
-	fn check(self) -> Result<Self, &'static str> {
+	fn check(self) -> Result<Self, TransactionValidityError> {
 		match self {
 			Extrinsic::AuthoritiesChange(new_auth) => Ok(Extrinsic::AuthoritiesChange(new_auth)),
 			Extrinsic::Transfer(transfer, signature) => {
 				if sr_primitives::verify_encoded_lazy(&signature, &transfer, &transfer.from) {
 					Ok(Extrinsic::Transfer(transfer, signature))
 				} else {
-					Err(sr_primitives::BAD_SIGNATURE)
+					Err(InvalidTransaction::BadProof.into())
 				}
 			},
-			Extrinsic::IncludeData(_) => Err(sr_primitives::BAD_SIGNATURE),
+			Extrinsic::IncludeData(_) => Err(InvalidTransaction::BadProof.into()),
 			Extrinsic::StorageChange(key, value) => Ok(Extrinsic::StorageChange(key, value)),
 		}
 	}
@@ -478,7 +480,7 @@ cfg_if! {
 			impl client_api::TaggedTransactionQueue<Block> for Runtime {
 				fn validate_transaction(utx: <Block as BlockT>::Extrinsic) -> TransactionValidity {
 					if let Extrinsic::IncludeData(data) = utx {
-						return TransactionValidity::Valid(ValidTransaction {
+						return Ok(ValidTransaction {
 							priority: data.len() as u64,
 							requires: vec![],
 							provides: vec![data],
@@ -662,7 +664,7 @@ cfg_if! {
 			impl client_api::TaggedTransactionQueue<Block> for Runtime {
 				fn validate_transaction(utx: <Block as BlockT>::Extrinsic) -> TransactionValidity {
 					if let Extrinsic::IncludeData(data) = utx {
-						return TransactionValidity::Valid(ValidTransaction{
+						return Ok(ValidTransaction{
 							priority: data.len() as u64,
 							requires: vec![],
 							provides: vec![data],

substrate/core/test-runtime/src/system.rs

@@ -21,12 +21,12 @@ use rstd::prelude::*;
 use runtime_io::{storage_root, ordered_trie_root, storage_changes_root, twox_128, blake2_256};
 use runtime_support::storage::{self, StorageValue, StorageMap};
 use runtime_support::storage_items;
-use sr_primitives::traits::{Hash as HashT, BlakeTwo256, Header as _};
-use sr_primitives::generic;
-use sr_primitives::{ApplyError, ApplyOutcome, ApplyResult};
-use sr_primitives::transaction_validity::{TransactionValidity, ValidTransaction};
+use sr_primitives::{
+	traits::{Hash as HashT, BlakeTwo256, Header as _}, generic, ApplyError, ApplyResult,
+	transaction_validity::{TransactionValidity, ValidTransaction, InvalidTransaction},
+};
 use codec::{KeyedVec, Encode};
-use super::{
+use crate::{
 	AccountId, BlockNumber, Extrinsic, Transfer, H256 as Hash, Block, Header, Digest, AuthorityId
 };
 use primitives::{Blake2Hasher, storage::well_known_keys};
@@ -119,7 +119,7 @@ fn execute_block_with_state_root_handler(
 	// execute transactions
 	block.extrinsics.iter().enumerate().for_each(|(i, e)| {
 		storage::unhashed::put(well_known_keys::EXTRINSIC_INDEX, &(i as u32));
-		execute_transaction_backend(e).unwrap_or_else(|_| panic!("Invalid transaction"));
+		let _ = execute_transaction_backend(e).unwrap_or_else(|_| panic!("Invalid transaction"));
 		storage::unhashed::kill(well_known_keys::EXTRINSIC_INDEX);
 	});
 
@@ -158,17 +158,17 @@ impl executive::ExecuteBlock<Block> for BlockExecutor {
 /// This doesn't attempt to validate anything regarding the block.
 pub fn validate_transaction(utx: Extrinsic) -> TransactionValidity {
 	if check_signature(&utx).is_err() {
-		return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+		return InvalidTransaction::BadProof.into();
 	}
 
 	let tx = utx.transfer();
 	let nonce_key = tx.from.to_keyed_vec(NONCE_OF);
 	let expected_nonce: u64 = storage::hashed::get_or(&blake2_256, &nonce_key, 0);
 	if tx.nonce < expected_nonce {
-		return TransactionValidity::Invalid(ApplyError::Stale as i8);
+		return InvalidTransaction::Stale.into();
 	}
 	if tx.nonce > expected_nonce + 64 {
-		return TransactionValidity::Unknown(ApplyError::Future as i8);
+		return InvalidTransaction::Future.into();
 	}
 
 	let hash = |from: &AccountId, nonce: u64| {
@@ -188,7 +188,7 @@ pub fn validate_transaction(utx: Extrinsic) -> TransactionValidity {
 		p
 	};
 
-	TransactionValidity::Valid(ValidTransaction {
+	Ok(ValidTransaction {
 		priority: tx.amount,
 		requires,
 		provides,
@@ -244,8 +244,7 @@ pub fn finalize_block() -> Header {
 #[inline(always)]
 fn check_signature(utx: &Extrinsic) -> Result<(), ApplyError> {
 	use sr_primitives::traits::BlindCheckable;
-	utx.clone().check().map_err(|_| ApplyError::BadSignature)?;
-	Ok(())
+	utx.clone().check().map_err(|_| InvalidTransaction::BadProof.into()).map(|_| ())
 }
 
 fn execute_transaction_backend(utx: &Extrinsic) -> ApplyResult {
@@ -253,7 +252,7 @@ fn execute_transaction_backend(utx: &Extrinsic) -> ApplyResult {
 	match utx {
 		Extrinsic::Transfer(ref transfer, _) => execute_transfer_backend(transfer),
 		Extrinsic::AuthoritiesChange(ref new_auth) => execute_new_authorities_backend(new_auth),
-		Extrinsic::IncludeData(_) => Ok(ApplyOutcome::Success),
+		Extrinsic::IncludeData(_) => Ok(Ok(())),
 		Extrinsic::StorageChange(key, value) => execute_storage_change(key, value.as_ref().map(|v| &**v)),
 	}
 }
@@ -263,7 +262,7 @@ fn execute_transfer_backend(tx: &Transfer) -> ApplyResult {
 	let nonce_key = tx.from.to_keyed_vec(NONCE_OF);
 	let expected_nonce: u64 = storage::hashed::get_or(&blake2_256, &nonce_key, 0);
 	if !(tx.nonce == expected_nonce) {
-		return Err(ApplyError::Stale)
+		return Err(InvalidTransaction::Stale.into());
 	}
 
 	// increment nonce in storage
@@ -275,18 +274,18 @@ fn execute_transfer_backend(tx: &Transfer) -> ApplyResult {
 
 	// enact transfer
 	if !(tx.amount <= from_balance) {
-		return Err(ApplyError::CantPay)
+		return Err(InvalidTransaction::Payment.into());
 	}
 	let to_balance_key = tx.to.to_keyed_vec(BALANCE_OF);
 	let to_balance: u64 = storage::hashed::get_or(&blake2_256, &to_balance_key, 0);
 	storage::hashed::put(&blake2_256, &from_balance_key, &(from_balance - tx.amount));
 	storage::hashed::put(&blake2_256, &to_balance_key, &(to_balance + tx.amount));
-	Ok(ApplyOutcome::Success)
+	Ok(Ok(()))
 }
 
 fn execute_new_authorities_backend(new_authorities: &[AuthorityId]) -> ApplyResult {
 	NewAuthorities::put(new_authorities.to_vec());
-	Ok(ApplyOutcome::Success)
+	Ok(Ok(()))
 }
 
 fn execute_storage_change(key: &[u8], value: Option<&[u8]>) -> ApplyResult {
@@ -294,7 +293,7 @@ fn execute_storage_change(key: &[u8], value: Option<&[u8]>) -> ApplyResult {
 		Some(value) => storage::unhashed::put_raw(key, value),
 		None => storage::unhashed::kill(key),
 	}
-	Ok(ApplyOutcome::Success)
+	Ok(Ok(()))
 }
 
 #[cfg(feature = "std")]
@@ -304,7 +303,7 @@ fn info_expect_equal_hash(given: &Hash, expected: &Hash) {
 		println!(
 			"Hash: given={}, expected={}",
 			HexDisplay::from(given.as_fixed_bytes()),
-			HexDisplay::from(expected.as_fixed_bytes())
+			HexDisplay::from(expected.as_fixed_bytes()),
 		);
 	}
 }
@@ -312,9 +311,9 @@ fn info_expect_equal_hash(given: &Hash, expected: &Hash) {
 #[cfg(not(feature = "std"))]
 fn info_expect_equal_hash(given: &Hash, expected: &Hash) {
 	if given != expected {
-		::runtime_io::print("Hash not equal");
-		::runtime_io::print(given.as_bytes());
-		::runtime_io::print(expected.as_bytes());
+		runtime_io::print("Hash not equal");
+		runtime_io::print(given.as_bytes());
+		runtime_io::print(expected.as_bytes());
 	}
 }
 

substrate/core/transaction-pool/graph/src/error.rs

@@ -16,7 +16,9 @@
 
 //! Transaction pool errors.
 
-use sr_primitives::transaction_validity::TransactionPriority as Priority;
+use sr_primitives::transaction_validity::{
+	TransactionPriority as Priority, InvalidTransaction, UnknownTransaction,
+};
 
 /// Transaction pool result.
 pub type Result<T> = std::result::Result<T, Error>;
@@ -25,11 +27,11 @@ pub type Result<T> = std::result::Result<T, Error>;
 #[derive(Debug, derive_more::Display, derive_more::From)]
 pub enum Error {
 	/// Transaction is not verifiable yet, but might be in the future.
-	#[display(fmt="Unkown Transaction Validity. Error code: {}", _0)]
-	UnknownTransactionValidity(i8),
+	#[display(fmt="Unknown transaction validity: {:?}", _0)]
+	UnknownTransaction(UnknownTransaction),
 	/// Transaction is invalid.
-	#[display(fmt="Invalid Transaction. Error Code: {}", _0)]
-	InvalidTransaction(i8),
+	#[display(fmt="Invalid transaction validity: {:?}", _0)]
+	InvalidTransaction(InvalidTransaction),
 	/// The transaction validity returned no "provides" tag.
 	///
 	/// Such transactions are not accepted to the pool, since we use those tags

substrate/core/transaction-pool/graph/src/pool.rs

@@ -34,7 +34,7 @@ use parking_lot::{Mutex, RwLock};
 use sr_primitives::{
 	generic::BlockId,
 	traits::{self, SaturatedConversion},
-	transaction_validity::{TransactionValidity, TransactionTag as Tag},
+	transaction_validity::{TransactionValidity, TransactionTag as Tag, TransactionValidityError},
 };
 
 pub use crate::base_pool::Limit;
@@ -129,7 +129,7 @@ impl<B: ChainApi> Pool<B> {
 				}
 
 				match self.api.validate_transaction(at, xt.clone())? {
-					TransactionValidity::Valid(validity) => if validity.provides.is_empty() {
+					Ok(validity) => if validity.provides.is_empty() {
 						Err(error::Error::NoTagsProvided.into())
 					} else {
 						Ok(base::Transaction {
@@ -145,12 +145,12 @@ impl<B: ChainApi> Pool<B> {
 								.saturating_add(validity.longevity),
 						})
 					},
-					TransactionValidity::Invalid(e) => {
+					Err(TransactionValidityError::Invalid(e)) => {
 						Err(error::Error::InvalidTransaction(e).into())
 					},
-					TransactionValidity::Unknown(e) => {
+					Err(TransactionValidityError::Unknown(e)) => {
 						self.listener.write().invalid(&hash);
-						Err(error::Error::UnknownTransactionValidity(e).into())
+						Err(error::Error::UnknownTransaction(e).into())
 					},
 				}
 			})
@@ -244,7 +244,7 @@ impl<B: ChainApi> Pool<B> {
 					None => {
 						let validity = self.api.validate_transaction(parent, extrinsic.clone());
 						match validity {
-							Ok(TransactionValidity::Valid(mut validity)) => {
+							Ok(Ok(mut validity)) => {
 								tags.append(&mut validity.provides);
 							},
 							// silently ignore invalid extrinsics,
@@ -453,7 +453,7 @@ fn fire_events<H, H2, Ex>(
 #[cfg(test)]
 mod tests {
 	use super::*;
-	use sr_primitives::transaction_validity::ValidTransaction;
+	use sr_primitives::transaction_validity::{ValidTransaction, InvalidTransaction};
 	use codec::Encode;
 	use test_runtime::{Block, Extrinsic, Transfer, H256, AccountId};
 	use assert_matches::assert_matches;
@@ -472,8 +472,11 @@ mod tests {
 		type Error = error::Error;
 
 		/// Verify extrinsic at given block.
-		fn validate_transaction(&self, at: &BlockId<Self::Block>, uxt: ExtrinsicFor<Self>) -> Result<TransactionValidity, Self::Error> {
-
+		fn validate_transaction(
+			&self,
+			at: &BlockId<Self::Block>,
+			uxt: ExtrinsicFor<Self>,
+		) -> Result<TransactionValidity, Self::Error> {
 			let block_number = self.block_id_to_number(at)?.unwrap();
 			let nonce = uxt.transfer().nonce;
 
@@ -488,9 +491,9 @@ mod tests {
 			}
 
 			if nonce < block_number {
-				Ok(TransactionValidity::Invalid(0))
+				Ok(InvalidTransaction::Stale.into())
 			} else {
-				Ok(TransactionValidity::Valid(ValidTransaction {
+				Ok(Ok(ValidTransaction {
 					priority: 4,
 					requires: if nonce > block_number { vec![vec![nonce as u8 - 1]] } else { vec![] },
 					provides: if nonce == INVALID_NONCE { vec![] } else { vec![vec![nonce as u8]] },

substrate/core/transaction-pool/src/tests.rs

@@ -39,7 +39,11 @@ impl txpool::ChainApi for TestApi {
 	type Hash = Hash;
 	type Error = error::Error;
 
-	fn validate_transaction(&self, at: &BlockId<Self::Block>, uxt: txpool::ExtrinsicFor<Self>) -> error::Result<TransactionValidity> {
+	fn validate_transaction(
+		&self,
+		at: &BlockId<Self::Block>,
+		uxt: txpool::ExtrinsicFor<Self>,
+	) -> error::Result<TransactionValidity> {
 		let expected = index(at);
 		let requires = if expected == uxt.transfer().nonce {
 			vec![]
@@ -48,13 +52,15 @@ impl txpool::ChainApi for TestApi {
 		};
 		let provides = vec![vec![uxt.transfer().nonce as u8]];
 
-		Ok(TransactionValidity::Valid(ValidTransaction {
-			priority: 1,
-			requires,
-			provides,
-			longevity: 64,
-			propagate: true,
-		}))
+		Ok(
+			Ok(ValidTransaction {
+				priority: 1,
+				requires,
+				provides,
+				longevity: 64,
+				propagate: true,
+			})
+		)
 	}
 
 	fn block_id_to_number(&self, at: &BlockId<Self::Block>) -> error::Result<Option<txpool::NumberFor<Self>>> {

substrate/node-template/runtime/src/lib.rs

@@ -235,7 +235,6 @@ impl balances::Trait for Runtime {
 	type OnNewAccount = Indices;
 	/// The ubiquitous event type.
 	type Event = Event;
-
 	type TransactionPayment = ();
 	type DustRemoval = ();
 	type TransferPayment = ();
@@ -268,7 +267,7 @@ construct_runtime!(
 		Babe: babe::{Module, Call, Storage, Config, Inherent(Timestamp)},
 		Grandpa: grandpa::{Module, Call, Storage, Config, Event},
 		Indices: indices::{default, Config<T>},
-		Balances: balances,
+		Balances: balances::{default, Error},
 		Sudo: sudo,
 		// Used for the module template in `./template.rs`
 		TemplateModule: template::{Module, Call, Storage, Event<T>},

substrate/node/cli/src/factory_impl.rs

@@ -56,7 +56,8 @@ impl<Number> FactoryState<Number> {
 			system::CheckEra::from(Era::mortal(256, phase)),
 			system::CheckNonce::from(index),
 			system::CheckWeight::new(),
-			balances::TakeFees::from(0)
+			balances::TakeFees::from(0),
+			Default::default(),
 		)
 	}
 }
@@ -147,7 +148,7 @@ impl RuntimeAdapter for FactoryState<Number> {
 					(*amount).into()
 				)
 			)
-		}, key, (version, genesis_hash.clone(), prior_block_hash.clone(), (), (), ()))
+		}, key, (version, genesis_hash.clone(), prior_block_hash.clone(), (), (), (), ()))
 	}
 
 	fn inherent_extrinsics(&self) -> InherentData {

substrate/node/cli/src/service.rs

@@ -470,11 +470,19 @@ mod tests {
 				let check_nonce = system::CheckNonce::from(index);
 				let check_weight = system::CheckWeight::new();
 				let take_fees = balances::TakeFees::from(0);
-				let extra = (check_version, check_genesis, check_era, check_nonce, check_weight, take_fees);
+				let extra = (
+					check_version,
+					check_genesis,
+					check_era,
+					check_nonce,
+					check_weight,
+					take_fees,
+					Default::default(),
+				);
 				let raw_payload = SignedPayload::from_raw(
 					function,
 					extra,
-					(version, genesis_hash, genesis_hash, (), (), ())
+					(version, genesis_hash, genesis_hash, (), (), (), ())
 				);
 				let signature = raw_payload.using_encoded(|payload|	{
 					signer.sign(payload)

substrate/node/executor/src/lib.rs

@@ -43,16 +43,16 @@ mod tests {
 	use runtime_support::{Hashable, StorageValue, StorageMap, assert_eq_error_rate, traits::Currency};
 	use state_machine::{CodeExecutor, Externalities, TestExternalities as CoreTestExternalities};
 	use primitives::{Blake2Hasher, NeverNativeValue, NativeOrEncoded, map};
-	use sr_primitives::traits::{Header as HeaderT, Hash as HashT, Convert};
-	use sr_primitives::{ApplyOutcome, ApplyError, ApplyResult};
-	use sr_primitives::weights::{WeightMultiplier, GetDispatchInfo};
+	use node_primitives::{Hash, BlockNumber, Balance};
+	use sr_primitives::{
+		traits::{Header as HeaderT, Hash as HashT, Convert}, ApplyOutcome, ApplyResult,
+		transaction_validity::InvalidTransaction, weights::{WeightMultiplier, GetDispatchInfo},
+	};
 	use contracts::ContractAddressFor;
 	use system::{EventRecord, Phase};
-	use node_primitives::{Hash, BlockNumber, Balance};
 	use node_runtime::{
 		Header, Block, UncheckedExtrinsic, CheckedExtrinsic, Call, Runtime, Balances, BuildStorage,
-		System, Event,
-		TransferFee, TransactionBaseFee, TransactionByteFee,
+		System, Event, TransferFee, TransactionBaseFee, TransactionByteFee,
 	};
 	use node_runtime::constants::currency::*;
 	use node_runtime::impls::WeightToFee;
@@ -150,7 +150,7 @@ mod tests {
 			None,
 		).0.unwrap();
 		let r = ApplyResult::decode(&mut &v.as_encoded()[..]).unwrap();
-		assert_eq!(r, Err(ApplyError::CantPay));
+		assert_eq!(r, Err(InvalidTransaction::Payment.into()));
 	}
 
 	#[test]
@@ -186,7 +186,7 @@ mod tests {
 			None,
 		).0.unwrap();
 		let r = ApplyResult::decode(&mut &v.as_encoded()[..]).unwrap();
-		assert_eq!(r, Err(ApplyError::CantPay));
+		assert_eq!(r, Err(InvalidTransaction::Payment.into()));
 	}
 
 	#[test]
@@ -763,7 +763,7 @@ mod tests {
 		let r = WasmExecutor::new()
 			.call(&mut t, 8, COMPACT_CODE, "BlockBuilder_apply_extrinsic", &vec![].and(&xt())).unwrap();
 		let r = ApplyResult::decode(&mut &r[..]).unwrap();
-		assert_eq!(r, Err(ApplyError::CantPay));
+		assert_eq!(r, Err(InvalidTransaction::Payment.into()));
 	}
 
 	#[test]
@@ -784,8 +784,10 @@ mod tests {
 		assert!(r.is_ok());
 		let r = WasmExecutor::new()
 			.call(&mut t, 8, COMPACT_CODE, "BlockBuilder_apply_extrinsic", &vec![].and(&xt())).unwrap();
-		let r = ApplyResult::decode(&mut &r[..]).unwrap();
-		assert_eq!(r, Ok(ApplyOutcome::Success));
+		ApplyResult::decode(&mut &r[..])
+			.unwrap()
+			.expect("Extrinsic could be applied")
+			.expect("Extrinsic did not fail");
 
 		runtime_io::with_externalities(&mut t, || {
 			assert_eq!(Balances::total_balance(&alice()), 42 * DOLLARS - 1 * transfer_fee(&xt()));

substrate/node/runtime/src/lib.rs

@@ -80,8 +80,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to equal spec_version. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 154,
-	impl_version: 159,
+	spec_version: 155,
+	impl_version: 155,
 	apis: RUNTIME_API_VERSIONS,
 };
 
@@ -445,6 +445,7 @@ impl system::offchain::CreateTransaction<Runtime, UncheckedExtrinsic> for Runtim
 			system::CheckNonce::<Runtime>::from(index),
 			system::CheckWeight::<Runtime>::new(),
 			balances::TakeFees::<Runtime>::from(tip),
+			Default::default(),
 		);
 		let raw_payload = SignedPayload::new(call, extra).ok()?;
 		let signature = F::sign(account.clone(), &raw_payload)?;
@@ -465,7 +466,7 @@ construct_runtime!(
 		Timestamp: timestamp::{Module, Call, Storage, Inherent},
 		Authorship: authorship::{Module, Call, Storage, Inherent},
 		Indices: indices,
-		Balances: balances,
+		Balances: balances::{default, Error},
 		Staking: staking::{default, OfflineWorker},
 		Session: session::{Module, Call, Storage, Event, Config<T>},
 		Democracy: democracy::{Module, Call, Storage, Config, Event<T>},
@@ -501,7 +502,8 @@ pub type SignedExtra = (
 	system::CheckEra<Runtime>,
 	system::CheckNonce<Runtime>,
 	system::CheckWeight<Runtime>,
-	balances::TakeFees<Runtime>
+	balances::TakeFees<Runtime>,
+	contracts::CheckBlockGasLimit<Runtime>,
 );
 /// Unchecked extrinsic type as expected by this runtime.
 pub type UncheckedExtrinsic = generic::UncheckedExtrinsic<Address, Call, Signature, SignedExtra>;

substrate/node/testing/src/keyring.rs

@@ -72,7 +72,8 @@ pub fn signed_extra(nonce: Index, extra_fee: Balance) -> SignedExtra {
 		system::CheckEra::from(Era::mortal(256, 0)),
 		system::CheckNonce::from(nonce),
 		system::CheckWeight::new(),
-		balances::TakeFees::from(extra_fee)
+		balances::TakeFees::from(extra_fee),
+		Default::default(),
 	)
 }
 

substrate/srml/balances/src/lib.rs

@@ -161,19 +161,26 @@
 use rstd::prelude::*;
 use rstd::{cmp, result, mem};
 use codec::{Codec, Encode, Decode};
-use support::{StorageValue, StorageMap, Parameter, decl_event, decl_storage, decl_module};
-use support::traits::{
-	UpdateBalanceOutcome, Currency, OnFreeBalanceZero, OnUnbalanced,
-	WithdrawReason, WithdrawReasons, LockIdentifier, LockableCurrency, ExistenceRequirement,
-	Imbalance, SignedImbalance, ReservableCurrency, Get,
+use support::{
+	StorageValue, StorageMap, Parameter, decl_event, decl_storage, decl_module,
+	traits::{
+		UpdateBalanceOutcome, Currency, OnFreeBalanceZero, OnUnbalanced,
+		WithdrawReason, WithdrawReasons, LockIdentifier, LockableCurrency, ExistenceRequirement,
+		Imbalance, SignedImbalance, ReservableCurrency, Get,
+	},
+	dispatch::Result,
 };
-use support::dispatch::Result;
-use sr_primitives::traits::{
-	Zero, SimpleArithmetic, StaticLookup, Member, CheckedAdd, CheckedSub, MaybeSerializeDebug,
-	Saturating, Bounded, SignedExtension, SaturatedConversion, DispatchError, Convert,
+use sr_primitives::{
+	transaction_validity::{
+		TransactionPriority, ValidTransaction, InvalidTransaction, TransactionValidityError,
+		TransactionValidity,
+	},
+	traits::{
+		Zero, SimpleArithmetic, StaticLookup, Member, CheckedAdd, CheckedSub, MaybeSerializeDebug,
+		Saturating, Bounded, SignedExtension, SaturatedConversion, Convert,
+	},
+	weights::{DispatchInfo, SimpleDispatchInfo, Weight},
 };
-use sr_primitives::transaction_validity::{TransactionPriority, ValidTransaction};
-use sr_primitives::weights::{DispatchInfo, SimpleDispatchInfo, Weight};
 use system::{IsDeadAccount, OnNewAccount, ensure_signed, ensure_root};
 
 mod mock;
@@ -1235,7 +1242,7 @@ impl<T: Trait<I>, I: Instance + Clone + Eq> SignedExtension for TakeFees<T, I> {
 	type Call = T::Call;
 	type AdditionalSigned = ();
 	type Pre = ();
-	fn additional_signed(&self) -> rstd::result::Result<(), &'static str> { Ok(()) }
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
 
 	fn validate(
 		&self,
@@ -1243,15 +1250,18 @@ impl<T: Trait<I>, I: Instance + Clone + Eq> SignedExtension for TakeFees<T, I> {
 		_call: &Self::Call,
 		info: DispatchInfo,
 		len: usize,
-	) -> rstd::result::Result<ValidTransaction, DispatchError> {
+	) -> TransactionValidity {
 		// pay any fees.
 		let fee = Self::compute_fee(len, info, self.0);
-		let imbalance = <Module<T, I>>::withdraw(
+		let imbalance = match <Module<T, I>>::withdraw(
 			who,
 			fee,
 			WithdrawReason::TransactionPayment,
 			ExistenceRequirement::KeepAlive,
-		).map_err(|_| DispatchError::Payment)?;
+		) {
+			Ok(imbalance) => imbalance,
+			Err(_) => return InvalidTransaction::Payment.into(),
+		};
 		T::TransactionPayment::on_unbalanced(imbalance);
 
 		let mut r = ValidTransaction::default();

substrate/srml/balances/src/tests.rs

@@ -232,7 +232,7 @@ fn default_indexing_on_new_accounts_should_not_work2() {
 			// ext_deposit is 10, value is 9, not satisfies for ext_deposit
 			assert_noop!(
 				Balances::transfer(Some(1).into(), 5, 9),
-				"value too low to create account"
+				"value too low to create account",
 			);
 			assert_eq!(Balances::is_dead_account(&5), true); // account 5 should not exist
 			assert_eq!(Balances::free_balance(&1), 100);
@@ -359,7 +359,7 @@ fn force_transfer_works() {
 		let _ = Balances::deposit_creating(&1, 111);
 		assert_noop!(
 			Balances::force_transfer(Some(2).into(), 1, 2, 69),
-			"bad origin: expected to be a root origin"
+			"RequireRootOrigin",
 		);
 		assert_ok!(Balances::force_transfer(RawOrigin::Root.into(), 1, 2, 69));
 		assert_eq!(Balances::total_balance(&1), 42);
@@ -389,7 +389,10 @@ fn balance_transfer_when_reserved_should_not_work() {
 	with_externalities(&mut ExtBuilder::default().build(), || {
 		let _ = Balances::deposit_creating(&1, 111);
 		assert_ok!(Balances::reserve(&1, 69));
-		assert_noop!(Balances::transfer(Some(1).into(), 2, 69), "balance too low to send value");
+		assert_noop!(
+			Balances::transfer(Some(1).into(), 2, 69),
+			"balance too low to send value",
+		);
 	});
 }
 
@@ -517,7 +520,7 @@ fn transferring_too_high_value_should_not_panic() {
 
 		assert_err!(
 			Balances::transfer(Some(1).into(), 2, u64::max_value()),
-			"destination balance too high to receive value"
+			"destination balance too high to receive value",
 		);
 
 		assert_eq!(Balances::free_balance(&1), u64::max_value());
@@ -595,7 +598,7 @@ fn transfer_overflow_isnt_exploitable() {
 
 			assert_err!(
 				Balances::transfer(Some(1).into(), 5, evil_value),
-				"got overflow after adding a fee to value"
+				"got overflow after adding a fee to value",
 			);
 		}
 	);
@@ -680,7 +683,7 @@ fn unvested_balance_should_not_transfer() {
 			assert_eq!(Balances::vesting_balance(&1), 45);
 			assert_noop!(
 				Balances::transfer(Some(1).into(), 2, 56),
-				"vesting balance too high to send value"
+				"vesting balance too high to send value",
 			); // Account 1 cannot send more than vested amount
 		}
 	);

substrate/srml/contracts/src/gas.rs

@@ -16,10 +16,12 @@
 
 use crate::{GasSpent, Module, Trait, BalanceOf, NegativeImbalanceOf};
 use rstd::convert::TryFrom;
-use sr_primitives::BLOCK_FULL;
-use sr_primitives::traits::{CheckedMul, Zero, SaturatedConversion, SimpleArithmetic, UniqueSaturatedInto};
-use support::StorageValue;
-use support::traits::{Currency, ExistenceRequirement, Get, Imbalance, OnUnbalanced, WithdrawReason};
+use sr_primitives::traits::{
+	CheckedMul, Zero, SaturatedConversion, SimpleArithmetic, UniqueSaturatedInto,
+};
+use support::{
+	traits::{Currency, ExistenceRequirement, Imbalance, OnUnbalanced, WithdrawReason}, StorageValue,
+};
 
 #[cfg(test)]
 use std::{any::Any, fmt::Debug};
@@ -200,14 +202,6 @@ pub fn buy_gas<T: Trait>(
 	transactor: &T::AccountId,
 	gas_limit: Gas,
 ) -> Result<(GasMeter<T>, NegativeImbalanceOf<T>), &'static str> {
-	// Check if the specified amount of gas is available in the current block.
-	// This cannot underflow since `gas_spent` is never greater than `T::BlockGasLimit`.
-	let gas_available = T::BlockGasLimit::get() - <Module<T>>::gas_spent();
-	if gas_limit > gas_available {
-		// gas limit reached, revert the transaction and retry again in the future
-		return Err(BLOCK_FULL);
-	}
-
 	// Buy the specified amount of gas.
 	let gas_price = <Module<T>>::gas_price();
 	let cost = if gas_price.is_zero() {

substrate/srml/contracts/src/lib.rs

@@ -63,6 +63,15 @@
 //! This creates a new smart contract account and calls its contract deploy handler to initialize the contract.
 //! * `call` - Makes a call to an account, optionally transferring some balance.
 //!
+//! ### Signed Extensions
+//!
+//! The contracts module defines the following extension:
+//!
+//!   - [`CheckBlockGasLimit`]: Ensures that the transaction does not exceeds the block gas limit.
+//!
+//! The signed extension needs to be added as signed extra to the transaction type to be used in the
+//! runtime.
+//!
 //! ## Usage
 //!
 //! The Contract module is a work in progress. The following examples show how this Contract module can be
@@ -100,15 +109,19 @@ use primitives::crypto::UncheckedFrom;
 use rstd::{prelude::*, marker::PhantomData};
 use codec::{Codec, Encode, Decode};
 use runtime_io::blake2_256;
-use sr_primitives::traits::{
-	Hash, StaticLookup, Zero, MaybeSerializeDebug, Member
+use sr_primitives::{
+	traits::{Hash, StaticLookup, Zero, MaybeSerializeDebug, Member, SignedExtension},
+	weights::DispatchInfo,
+	transaction_validity::{
+		ValidTransaction, InvalidTransaction, TransactionValidity, TransactionValidityError,
+	},
 };
 use support::dispatch::{Result, Dispatchable};
 use support::{
 	Parameter, StorageMap, StorageValue, decl_module, decl_event, decl_storage, storage::child,
 	parameter_types,
 };
-use support::traits::{OnFreeBalanceZero, OnUnbalanced, Currency, Get};
+use support::{traits::{OnFreeBalanceZero, OnUnbalanced, Currency, Get}, IsSubType};
 use system::{ensure_signed, RawOrigin, ensure_root};
 use primitives::storage::well_known_keys::CHILD_STORAGE_KEY_PREFIX;
 use timestamp;
@@ -321,7 +334,7 @@ pub trait Trait: timestamp::Trait {
 	type Currency: Currency<Self::AccountId>;
 
 	/// The outer call dispatch type.
-	type Call: Parameter + Dispatchable<Origin=<Self as system::Trait>::Origin>;
+	type Call: Parameter + Dispatchable<Origin=<Self as system::Trait>::Origin> + IsSubType<Module<Self>, Self>;
 
 	/// The overarching event type.
 	type Event: From<Event<Self>> + Into<<Self as system::Trait>::Event>;
@@ -597,15 +610,17 @@ decl_module! {
 		/// the sender is not eligible for the reward.
 		fn claim_surcharge(origin, dest: T::AccountId, aux_sender: Option<T::AccountId>) {
 			let origin = origin.into();
-			let (signed, rewarded) = match origin {
-				Ok(system::RawOrigin::Signed(ref account)) if aux_sender.is_none() => {
+			let (signed, rewarded) = match (origin, aux_sender) {
+				(Ok(system::RawOrigin::Signed(account)), None) => {
 					(true, account)
 				},
-				Ok(system::RawOrigin::None) if aux_sender.is_some() => {
-					(false, aux_sender.as_ref().expect("checked above"))
+				(Ok(system::RawOrigin::None), Some(aux_sender)) => {
+					(false, aux_sender)
 				},
-				_ => return Err("Invalid surcharge claim: origin must be signed or \
-								inherent and auxiliary sender only provided on inherent")
+				_ => return 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
@@ -619,7 +634,7 @@ decl_module! {
 
 			// If poking the contract has lead to eviction of the contract, give out the rewards.
 			if rent::try_evict::<T>(&dest, handicap) == rent::RentOutcome::Evicted {
-				T::Currency::deposit_into_existing(rewarded, T::SurchargeReward::get())?;
+				T::Currency::deposit_into_existing(&rewarded, T::SurchargeReward::get())?;
 			}
 		}
 
@@ -937,3 +952,62 @@ impl Default for Schedule {
 		}
 	}
 }
+
+/// `SignedExtension` that checks if a transaction would exhausts the block gas limit.
+#[derive(Encode, Decode, Clone, Eq, PartialEq)]
+pub struct CheckBlockGasLimit<T: Trait + Send + Sync>(PhantomData<T>);
+
+impl<T: Trait + Send + Sync> Default for CheckBlockGasLimit<T> {
+	fn default() -> Self {
+		Self(PhantomData)
+	}
+}
+
+#[cfg(feature = "std")]
+impl<T: Trait + Send + Sync> std::fmt::Debug for CheckBlockGasLimit<T> {
+	fn fmt(&self, _: &mut std::fmt::Formatter) -> std::fmt::Result {
+		Ok(())
+	}
+}
+
+impl<T: Trait + Send + Sync> SignedExtension for CheckBlockGasLimit<T> {
+	type AccountId = T::AccountId;
+	type Call = <T as Trait>::Call;
+	type AdditionalSigned = ();
+	type Pre = ();
+
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
+
+	fn validate(
+		&self,
+		_: &Self::AccountId,
+		call: &Self::Call,
+		_: DispatchInfo,
+		_: usize,
+	) -> TransactionValidity {
+		let call = match call.is_sub_type() {
+			Some(call) => call,
+			None => return Ok(ValidTransaction::default()),
+		};
+
+		match call {
+			Call::claim_surcharge(_, _) | Call::update_schedule(_) =>
+				Ok(ValidTransaction::default()),
+			Call::put_code(gas_limit, _)
+				| Call::call(_, _, gas_limit, _)
+				| Call::create(_, gas_limit, _, _)
+			=> {
+				// Check if the specified amount of gas is available in the current block.
+				// This cannot underflow since `gas_spent` is never greater than `T::BlockGasLimit`.
+				let gas_available = T::BlockGasLimit::get() - <Module<T>>::gas_spent();
+				if *gas_limit > gas_available {
+					// gas limit reached, revert the transaction and retry again in the future
+					InvalidTransaction::ExhaustsResources.into()
+				} else {
+					Ok(ValidTransaction::default())
+				}
+			},
+			Call::__PhantomItem(_, _)  => unreachable!("Variant is never constructed"),
+		}
+	}
+}

substrate/srml/contracts/src/tests.rs

@@ -22,27 +22,27 @@
 use crate::account_db::{AccountDb, DirectAccountDb, OverlayAccountDb};
 use crate::{
 	BalanceOf, ComputeDispatchFee, ContractAddressFor, ContractInfo, ContractInfoOf, GenesisConfig,
-	Module, RawAliveContractInfo, RawEvent, Trait, TrieId, TrieIdFromParentCounter,
-	TrieIdGenerator, Schedule,
+	Module, RawAliveContractInfo, RawEvent, Trait, TrieId, TrieIdFromParentCounter, Schedule,
+	TrieIdGenerator, CheckBlockGasLimit,
 };
 use assert_matches::assert_matches;
 use hex_literal::*;
 use codec::{Decode, Encode, KeyedVec};
 use runtime_io;
 use runtime_io::with_externalities;
-use sr_primitives::testing::{Digest, DigestItem, Header, UintAuthorityId, H256};
-use sr_primitives::traits::{BlakeTwo256, Hash, IdentityLookup};
-use sr_primitives::{Perbill, BuildStorage};
+use sr_primitives::{
+	Perbill, BuildStorage, transaction_validity::{InvalidTransaction, ValidTransaction},
+	traits::{BlakeTwo256, Hash, IdentityLookup, SignedExtension},
+	weights::{DispatchInfo, DispatchClass},
+	testing::{Digest, DigestItem, Header, UintAuthorityId, H256},
+};
 use support::{
 	assert_ok, assert_err, impl_outer_dispatch, impl_outer_event, impl_outer_origin, parameter_types,
 	storage::child, StorageMap, StorageValue, traits::{Currency, Get},
 };
-use std::cell::RefCell;
-use std::sync::atomic::{AtomicUsize, Ordering};
-use primitives::storage::well_known_keys;
-use primitives::Blake2Hasher;
+use std::{cell::RefCell, sync::atomic::{AtomicUsize, Ordering}};
+use primitives::{storage::well_known_keys, Blake2Hasher};
 use system::{self, EventRecord, Phase};
-use {balances, wabt};
 
 mod contract {
 	// Re-export contents of the root. This basically
@@ -2390,3 +2390,22 @@ fn cannot_self_destruct_in_constructor() {
 		}
 	);
 }
+
+#[test]
+fn check_block_gas_limit_works() {
+	with_externalities(
+		&mut ExtBuilder::default().block_gas_limit(50).build(),
+		|| {
+			let info = DispatchInfo { weight: 100, class: DispatchClass::Normal };
+			let check = CheckBlockGasLimit::<Test>(Default::default());
+			let call: Call = crate::Call::put_code(1000, vec![]).into();
+
+			assert_eq!(
+				check.validate(&0, &call, info, 0), InvalidTransaction::ExhaustsResources.into(),
+			);
+
+			let call: Call = crate::Call::update_schedule(Default::default()).into();
+			assert_eq!(check.validate(&0, &call, info, 0), Ok(Default::default()));
+		}
+	);
+}

substrate/srml/council/src/lib.rs

@@ -62,6 +62,8 @@ mod tests {
 
 	impl_outer_dispatch! {
 		pub enum Call for Test where origin: Origin {
+			type Error = Error;
+
 			balances::Balances,
 			democracy::Democracy,
 		}
@@ -115,6 +117,7 @@ mod tests {
 		type Header = Header;
 		type WeightMultiplierUpdate = ();
 		type Event = Event;
+		type Error = Error;
 		type BlockHashCount = BlockHashCount;
 		type MaximumBlockWeight = MaximumBlockWeight;
 		type MaximumBlockLength = MaximumBlockLength;
@@ -136,6 +139,7 @@ mod tests {
 		type TransactionPayment = ();
 		type TransferPayment = ();
 		type DustRemoval = ();
+		type Error = Error;
 		type ExistentialDeposit = ExistentialDeposit;
 		type TransferFee = TransferFee;
 		type CreationFee = CreationFee;

substrate/srml/democracy/src/lib.rs

@@ -20,12 +20,14 @@
 
 use rstd::prelude::*;
 use rstd::{result, convert::TryFrom};
-use sr_primitives::traits::{Zero, Bounded, CheckedMul, CheckedDiv, EnsureOrigin, Hash};
-use sr_primitives::weights::SimpleDispatchInfo;
+use sr_primitives::{
+	traits::{Zero, Bounded, CheckedMul, CheckedDiv, EnsureOrigin, Hash, Dispatchable},
+	weights::SimpleDispatchInfo,
+};
 use codec::{Encode, Decode, Input, Output, Error};
 use support::{
 	decl_module, decl_storage, decl_event, ensure, StorageValue, StorageMap, StorageLinkedMap,
-	Parameter, Dispatchable,
+	Parameter,
 	traits::{
 		Currency, ReservableCurrency, LockableCurrency, WithdrawReason, LockIdentifier, Get,
 		OnFreeBalanceZero

substrate/srml/elections/src/lib.rs

@@ -504,7 +504,7 @@ decl_module! {
 			let who = ensure_signed(origin)?;
 			ensure!(
 				!total.is_zero(),
-				"stake deposited to present winner and be added to leaderboard should be non-zero"
+				"stake deposited to present winner and be added to leaderboard should be non-zero",
 			);
 
 			let candidate = T::Lookup::lookup(candidate)?;
@@ -1234,7 +1234,7 @@ mod tests {
 			UncheckedExtrinsic = UncheckedExtrinsic
 		{
 			System: system::{Module, Call, Event},
-			Balances: balances::{Module, Call, Event<T>, Config<T>},
+			Balances: balances::{Module, Call, Event<T>, Config<T>, Error},
 			Elections: elections::{Module, Call, Event<T>, Config<T>},
 		}
 	);

substrate/srml/example/src/lib.rs

@@ -258,9 +258,10 @@ use support::{StorageValue, dispatch::Result, decl_module, decl_storage, decl_ev
 use system::{ensure_signed, ensure_root};
 use codec::{Encode, Decode};
 use sr_primitives::{
-	traits::{SignedExtension, DispatchError, Bounded},
-	transaction_validity::ValidTransaction,
-	weights::{SimpleDispatchInfo, DispatchInfo},
+	traits::{SignedExtension, Bounded}, weights::{SimpleDispatchInfo, DispatchInfo},
+	transaction_validity::{
+		ValidTransaction, TransactionValidityError, InvalidTransaction, TransactionValidity,
+	},
 };
 
 /// Our module's configuration trait. All our types and consts go in here. If the
@@ -561,7 +562,7 @@ impl<T: Trait + Send + Sync> SignedExtension for WatchDummy<T> {
 	type AdditionalSigned = ();
 	type Pre = ();
 
-	fn additional_signed(&self) -> rstd::result::Result<(), &'static str> { Ok(()) }
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
 
 	fn validate(
 		&self,
@@ -569,9 +570,11 @@ impl<T: Trait + Send + Sync> SignedExtension for WatchDummy<T> {
 		call: &Self::Call,
 		_info: DispatchInfo,
 		len: usize,
-	) -> rstd::result::Result<ValidTransaction, DispatchError> {
+	) -> TransactionValidity {
 		// if the transaction is too big, just drop it.
-		if len > 200 { return Err(DispatchError::Exhausted) }
+		if len > 200 {
+			return InvalidTransaction::ExhaustsResources.into()
+		}
 
 		// check for `set_dummy`
 		match call {
@@ -582,7 +585,7 @@ impl<T: Trait + Send + Sync> SignedExtension for WatchDummy<T> {
 				valid_tx.priority = Bounded::max_value();
 				Ok(valid_tx)
 			}
-			_ => Ok(Default::default())
+			_ => Ok(Default::default()),
 		}
 	}
 }
@@ -712,12 +715,14 @@ mod tests {
 			let info = DispatchInfo::default();
 
 			assert_eq!(
-				WatchDummy::<Test>(PhantomData).validate(&1, &call, info, 150).unwrap().priority,
-				Bounded::max_value()
+				WatchDummy::<Test>(PhantomData).validate(&1, &call, info, 150)
+					.unwrap()
+					.priority,
+				Bounded::max_value(),
 			);
 			assert_eq!(
 				WatchDummy::<Test>(PhantomData).validate(&1, &call, info, 250),
-				Err(DispatchError::Exhausted)
+				InvalidTransaction::ExhaustsResources.into(),
 			);
 		})
 	}

substrate/srml/executive/src/lib.rs

@@ -59,13 +59,13 @@
 //! # pub type Balances = u64;
 //! # pub type AllModules = u64;
 //! # pub enum Runtime {};
-//! # use sr_primitives::transaction_validity::TransactionValidity;
+//! # use sr_primitives::transaction_validity::{TransactionValidity, UnknownTransaction};
 //! # use sr_primitives::traits::ValidateUnsigned;
 //! # impl ValidateUnsigned for Runtime {
 //! # 	type Call = ();
 //! #
 //! # 	fn validate_unsigned(_call: &Self::Call) -> TransactionValidity {
-//! # 		TransactionValidity::Invalid(0)
+//! # 		UnknownTransaction::NoUnsignedValidator.into()
 //! # 	}
 //! # }
 //! /// Executive: handles dispatch to the various modules.
@@ -74,50 +74,17 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use rstd::prelude::*;
-use rstd::marker::PhantomData;
-use rstd::result;
-use sr_primitives::{generic::Digest, traits::{
-	self, Header, Zero, One, Checkable, Applyable, CheckEqual, OnFinalize,
-	OnInitialize, NumberFor, Block as BlockT, OffchainWorker, ValidateUnsigned
-}};
-use support::Dispatchable;
+use rstd::{prelude::*, marker::PhantomData};
+use sr_primitives::{
+	generic::Digest, ApplyResult, weights::GetDispatchInfo,
+	traits::{
+		self, Header, Zero, One, Checkable, Applyable, CheckEqual, OnFinalize, OnInitialize,
+		NumberFor, Block as BlockT, OffchainWorker, ValidateUnsigned, Dispatchable
+	},
+	transaction_validity::TransactionValidity,
+};
 use codec::{Codec, Encode};
 use system::{extrinsics_root, DigestOf};
-use sr_primitives::{ApplyOutcome, ApplyError};
-use sr_primitives::transaction_validity::TransactionValidity;
-use sr_primitives::weights::GetDispatchInfo;
-
-mod internal {
-	use sr_primitives::traits::DispatchError;
-
-	pub enum ApplyError {
-		BadSignature(&'static str),
-		Stale,
-		Future,
-		CantPay,
-		FullBlock,
-	}
-
-	pub enum ApplyOutcome {
-		Success,
-		Fail(&'static str),
-	}
-
-	impl From<DispatchError> for ApplyError {
-		fn from(d: DispatchError) -> Self {
-			match d {
-				DispatchError::Payment => ApplyError::CantPay,
-				DispatchError::Exhausted => ApplyError::FullBlock,
-				DispatchError::NoPermission => ApplyError::CantPay,
-				DispatchError::BadState => ApplyError::CantPay,
-				DispatchError::Stale => ApplyError::Stale,
-				DispatchError::Future => ApplyError::Future,
-				DispatchError::BadProof => ApplyError::BadSignature(""),
-			}
-		}
-	}
-}
 
 /// Trait that can be used to execute a block.
 pub trait ExecuteBlock<Block: BlockT> {
@@ -239,30 +206,19 @@ where
 	/// Apply extrinsic outside of the block execution function.
 	/// This doesn't attempt to validate anything regarding the block, but it builds a list of uxt
 	/// hashes.
-	pub fn apply_extrinsic(uxt: Block::Extrinsic) -> result::Result<ApplyOutcome, ApplyError> {
+	pub fn apply_extrinsic(uxt: Block::Extrinsic) -> ApplyResult {
 		let encoded = uxt.encode();
 		let encoded_len = encoded.len();
-		match Self::apply_extrinsic_with_len(uxt, encoded_len, Some(encoded)) {
-			Ok(internal::ApplyOutcome::Success) => Ok(ApplyOutcome::Success),
-			Ok(internal::ApplyOutcome::Fail(_)) => Ok(ApplyOutcome::Fail),
-			Err(internal::ApplyError::CantPay) => Err(ApplyError::CantPay),
-			Err(internal::ApplyError::BadSignature(_)) => Err(ApplyError::BadSignature),
-			Err(internal::ApplyError::Stale) => Err(ApplyError::Stale),
-			Err(internal::ApplyError::Future) => Err(ApplyError::Future),
-			Err(internal::ApplyError::FullBlock) => Err(ApplyError::FullBlock),
-		}
+		Self::apply_extrinsic_with_len(uxt, encoded_len, Some(encoded))
 	}
 
 	/// Apply an extrinsic inside the block execution function.
 	fn apply_extrinsic_no_note(uxt: Block::Extrinsic) {
 		let l = uxt.encode().len();
 		match Self::apply_extrinsic_with_len(uxt, l, None) {
-			Ok(internal::ApplyOutcome::Success) => (),
-			Ok(internal::ApplyOutcome::Fail(e)) => runtime_io::print(e),
-			Err(internal::ApplyError::CantPay) => panic!("All extrinsics should have sender able to pay their fees"),
-			Err(internal::ApplyError::BadSignature(_)) => panic!("All extrinsics should be properly signed"),
-			Err(internal::ApplyError::Stale) | Err(internal::ApplyError::Future) => panic!("All extrinsics should have the correct nonce"),
-			Err(internal::ApplyError::FullBlock) => panic!("Extrinsics should not exceed block limit"),
+			Ok(Ok(())) => (),
+			Ok(Err(e)) => runtime_io::print(e),
+			Err(e) => { let err: &'static str = e.into(); panic!(err) },
 		}
 	}
 
@@ -271,9 +227,9 @@ where
 		uxt: Block::Extrinsic,
 		encoded_len: usize,
 		to_note: Option<Vec<u8>>,
-	) -> result::Result<internal::ApplyOutcome, internal::ApplyError> {
+	) -> ApplyResult {
 		// Verify that the signature is good.
-		let xt = uxt.check(&Default::default()).map_err(internal::ApplyError::BadSignature)?;
+		let xt = uxt.check(&Default::default())?;
 
 		// We don't need to make sure to `note_extrinsic` only after we know it's going to be
 		// executed to prevent it from leaking in storage since at this point, it will either
@@ -286,15 +242,11 @@ where
 
 		// Decode parameters and dispatch
 		let dispatch_info = xt.get_dispatch_info();
-		let r = Applyable::dispatch(xt, dispatch_info, encoded_len)
-			.map_err(internal::ApplyError::from)?;
+		let r = Applyable::apply(xt, dispatch_info, encoded_len)?;
 
 		<system::Module<System>>::note_applied_extrinsic(&r, encoded_len as u32);
 
-		r.map(|_| internal::ApplyOutcome::Success).or_else(|e| match e {
-			sr_primitives::BLOCK_FULL => Err(internal::ApplyError::FullBlock),
-			e => Ok(internal::ApplyOutcome::Fail(e))
-		})
+		Ok(r)
 	}
 
 	fn final_checks(header: &System::Header) {
@@ -324,21 +276,8 @@ where
 	///
 	/// Changes made to storage should be discarded.
 	pub fn validate_transaction(uxt: Block::Extrinsic) -> TransactionValidity {
-		// Note errors > 0 are from ApplyError
-		const UNKNOWN_ERROR: i8 = -127;
-		const INVALID_INDEX: i8 = -10;
-
 		let encoded_len = uxt.using_encoded(|d| d.len());
-		let xt = match uxt.check(&Default::default()) {
-			// Checks out. Carry on.
-			Ok(xt) => xt,
-			// An unknown account index implies that the transaction may yet become valid.
-			Err("invalid account index") => return TransactionValidity::Unknown(INVALID_INDEX),
-			// Technically a bad signature could also imply an out-of-date account index, but
-			// that's more of an edge case.
-			Err(sr_primitives::BAD_SIGNATURE) => return TransactionValidity::Invalid(ApplyError::BadSignature as i8),
-			Err(_) => return TransactionValidity::Invalid(UNKNOWN_ERROR),
-		};
+		let xt = uxt.check(&Default::default())?;
 
 		let dispatch_info = xt.get_dispatch_info();
 		xt.validate::<UnsignedValidator>(dispatch_info, encoded_len)
@@ -357,13 +296,15 @@ mod tests {
 	use balances::Call;
 	use runtime_io::with_externalities;
 	use primitives::{H256, Blake2Hasher};
-	use sr_primitives::generic::Era;
-	use sr_primitives::Perbill;
-	use sr_primitives::weights::Weight;
-	use sr_primitives::traits::{Header as HeaderT, BlakeTwo256, IdentityLookup, ConvertInto};
-	use sr_primitives::testing::{Digest, Header, Block};
-	use support::{impl_outer_event, impl_outer_origin, parameter_types};
-	use support::traits::{Currency, LockIdentifier, LockableCurrency, WithdrawReasons, WithdrawReason};
+	use sr_primitives::{
+		generic::Era, Perbill, DispatchError, weights::Weight, testing::{Digest, Header, Block},
+		traits::{Header as HeaderT, BlakeTwo256, IdentityLookup, ConvertInto},
+		transaction_validity::{InvalidTransaction, UnknownTransaction}, ApplyError,
+	};
+	use support::{
+		impl_outer_event, impl_outer_origin, parameter_types,
+		traits::{Currency, LockIdentifier, LockableCurrency, WithdrawReasons, WithdrawReason},
+	};
 	use system;
 	use hex_literal::hex;
 
@@ -432,8 +373,8 @@ mod tests {
 
 		fn validate_unsigned(call: &Self::Call) -> TransactionValidity {
 			match call {
-				Call::set_balance(_, _, _) => TransactionValidity::Valid(Default::default()),
-				_ => TransactionValidity::Invalid(0),
+				Call::set_balance(_, _, _) => Ok(Default::default()),
+				_ => UnknownTransaction::NoUnsignedValidator.into(),
 			}
 		}
 	}
@@ -479,7 +420,7 @@ mod tests {
 				Digest::default(),
 			));
 			let r = Executive::apply_extrinsic(xt);
-			assert_eq!(r, Ok(ApplyOutcome::Success));
+			assert!(r.is_ok());
 			assert_eq!(<balances::Module<Runtime>>::total_balance(&1), 142 - 10 - weight);
 			assert_eq!(<balances::Module<Runtime>>::total_balance(&2), 69);
 		});
@@ -582,14 +523,19 @@ mod tests {
 			assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), 0);
 
 			for nonce in 0..=num_to_exhaust_block {
-				let xt = sr_primitives::testing::TestXt(sign_extra(1, nonce.into(), 0), Call::transfer::<Runtime>(33, 0));
+				let xt = sr_primitives::testing::TestXt(
+					sign_extra(1, nonce.into(), 0), Call::transfer::<Runtime>(33, 0),
+				);
 				let res = Executive::apply_extrinsic(xt);
 				if nonce != num_to_exhaust_block {
-					assert_eq!(res.unwrap(), ApplyOutcome::Success);
-					assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), encoded_len * (nonce + 1));
+					assert!(res.is_ok());
+					assert_eq!(
+						<system::Module<Runtime>>::all_extrinsics_weight(),
+						encoded_len * (nonce + 1),
+					);
 					assert_eq!(<system::Module<Runtime>>::extrinsic_index(), Some(nonce as u32 + 1));
 				} else {
-					assert_eq!(res, Err(ApplyError::FullBlock));
+					assert_eq!(res, Err(InvalidTransaction::ExhaustsResources.into()));
 				}
 			}
 		});
@@ -606,9 +552,9 @@ mod tests {
 			assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), 0);
 			assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), 0);
 
-			assert_eq!(Executive::apply_extrinsic(xt.clone()).unwrap(), ApplyOutcome::Success);
-			assert_eq!(Executive::apply_extrinsic(x1.clone()).unwrap(), ApplyOutcome::Success);
-			assert_eq!(Executive::apply_extrinsic(x2.clone()).unwrap(), ApplyOutcome::Success);
+			assert!(Executive::apply_extrinsic(xt.clone()).unwrap().is_ok());
+			assert!(Executive::apply_extrinsic(x1.clone()).unwrap().is_ok());
+			assert!(Executive::apply_extrinsic(x2.clone()).unwrap().is_ok());
 
 			// default weight for `TestXt` == encoded length.
 			assert_eq!(<system::Module<Runtime>>::all_extrinsics_weight(), (3 * len).into());
@@ -624,12 +570,18 @@ mod tests {
 	#[test]
 	fn validate_unsigned() {
 		let xt = sr_primitives::testing::TestXt(None, Call::set_balance(33, 69, 69));
-		let valid = TransactionValidity::Valid(Default::default());
 		let mut t = new_test_ext(1);
 
 		with_externalities(&mut t, || {
-			assert_eq!(Executive::validate_transaction(xt.clone()), valid);
-			assert_eq!(Executive::apply_extrinsic(xt), Ok(ApplyOutcome::Fail));
+			assert_eq!(Executive::validate_transaction(xt.clone()), Ok(Default::default()));
+			assert_eq!(
+				Executive::apply_extrinsic(xt),
+				Ok(
+					Err(
+						DispatchError { module: None, error: 0, message: Some("RequireRootOrigin") }
+					)
+				)
+			);
 		});
 	}
 
@@ -657,11 +609,21 @@ mod tests {
 				));
 
 				if lock == WithdrawReasons::except(WithdrawReason::TransactionPayment) {
-					assert_eq!(Executive::apply_extrinsic(xt).unwrap(), ApplyOutcome::Fail);
+					assert_eq!(
+						Executive::apply_extrinsic(xt).unwrap(),
+						Err(DispatchError {
+							module: None,
+							error: 0,
+							message: Some("account liquidity restrictions prevent withdrawal"),
+						}),
+					);
 					// but tx fee has been deducted. the transaction failed on transfer, not on fee.
 					assert_eq!(<balances::Module<Runtime>>::total_balance(&1), 111 - 10 - weight);
 				} else {
-					assert_eq!(Executive::apply_extrinsic(xt), Err(ApplyError::CantPay));
+					assert_eq!(
+						Executive::apply_extrinsic(xt),
+						Err(ApplyError::Validity(InvalidTransaction::Payment.into())),
+					);
 					assert_eq!(<balances::Module<Runtime>>::total_balance(&1), 111);
 				}
 			});

substrate/srml/grandpa/src/mock.rs

@@ -37,9 +37,9 @@ pub fn grandpa_log(log: ConsensusLog<u64>) -> DigestItem<H256> {
 // Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
 #[derive(Clone, PartialEq, Eq, Debug, Decode, Encode)]
 pub struct Test;
+
 impl Trait for Test {
 	type Event = TestEvent;
-
 }
 parameter_types! {
 	pub const BlockHashCount: u64 = 250;
@@ -53,7 +53,7 @@ impl system::Trait for Test {
 	type BlockNumber = u64;
 	type Call = ();
 	type Hash = H256;
-	type Hashing = ::sr_primitives::traits::BlakeTwo256;
+	type Hashing = sr_primitives::traits::BlakeTwo256;
 	type AccountId = u64;
 	type Lookup = IdentityLookup<Self::AccountId>;
 	type Header = Header;

substrate/srml/im-online/src/lib.rs

@@ -74,9 +74,10 @@ use rstd::prelude::*;
 use session::historical::IdentificationTuple;
 use runtime_io::Printable;
 use sr_primitives::{
-	Perbill, ApplyError,
-	traits::{Convert, Member},
-	transaction_validity::{TransactionValidity, TransactionLongevity, ValidTransaction},
+	traits::{Convert, Member}, Perbill,
+	transaction_validity::{
+		TransactionValidity, TransactionLongevity, ValidTransaction, InvalidTransaction,
+	},
 };
 use sr_staking_primitives::{
 	SessionIndex, CurrentElectedSet,
@@ -160,7 +161,7 @@ enum OffchainErr {
 }
 
 impl Printable for OffchainErr {
-	fn print(self) {
+	fn print(&self) {
 		match self {
 			OffchainErr::DecodeWorkerStatus => print("Offchain error: decoding WorkerStatus failed!"),
 			OffchainErr::FailedSigning => print("Offchain error: signing failed!"),
@@ -489,24 +490,24 @@ impl<T: Trait> session::OneSessionHandler<T::AccountId> for Module<T> {
 impl<T: Trait> support::unsigned::ValidateUnsigned for Module<T> {
 	type Call = Call<T>;
 
-	fn validate_unsigned(call: &Self::Call) -> support::unsigned::TransactionValidity {
+	fn validate_unsigned(call: &Self::Call) -> TransactionValidity {
 		if let Call::heartbeat(heartbeat, signature) = call {
 			if <Module<T>>::is_online_in_current_session(heartbeat.authority_index) {
 				// we already received a heartbeat for this authority
-				return TransactionValidity::Invalid(ApplyError::Stale as i8);
+				return InvalidTransaction::Stale.into();
 			}
 
 			// check if session index from heartbeat is recent
 			let current_session = <session::Module<T>>::current_index();
 			if heartbeat.session_index != current_session {
-				return TransactionValidity::Invalid(ApplyError::Stale as i8);
+				return InvalidTransaction::Stale.into();
 			}
 
 			// verify that the incoming (unverified) pubkey is actually an authority id
 			let keys = Keys::<T>::get();
 			let authority_id = match keys.get(heartbeat.authority_index as usize) {
 				Some(id) => id,
-				None => return TransactionValidity::Invalid(ApplyError::BadSignature as i8),
+				None => return InvalidTransaction::BadProof.into(),
 			};
 
 			// check signature (this is expensive so we do it last).
@@ -515,19 +516,19 @@ impl<T: Trait> support::unsigned::ValidateUnsigned for Module<T> {
 			});
 
 			if !signature_valid {
-				return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+				return InvalidTransaction::BadProof.into();
 			}
 
-			return TransactionValidity::Valid(ValidTransaction {
+			Ok(ValidTransaction {
 				priority: 0,
 				requires: vec![],
 				provides: vec![(current_session, authority_id).encode()],
 				longevity: TransactionLongevity::max_value(),
 				propagate: true,
 			})
+		} else {
+			InvalidTransaction::Call.into()
 		}
-
-		TransactionValidity::Invalid(0)
 	}
 }
 

substrate/srml/indices/src/lib.rs

@@ -19,10 +19,10 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use rstd::{prelude::*, result, marker::PhantomData, convert::TryInto};
+use rstd::{prelude::*, marker::PhantomData, convert::TryInto};
 use codec::{Encode, Codec};
 use support::{StorageValue, StorageMap, Parameter, decl_module, decl_event, decl_storage};
-use sr_primitives::traits::{One, SimpleArithmetic, StaticLookup, Member};
+use sr_primitives::traits::{One, SimpleArithmetic, StaticLookup, Member, LookupError};
 use system::{IsDeadAccount, OnNewAccount};
 
 use self::address::Address as RawAddress;
@@ -224,9 +224,11 @@ impl<T: Trait> OnNewAccount<T::AccountId> for Module<T> {
 impl<T: Trait> StaticLookup for Module<T> {
 	type Source = address::Address<T::AccountId, T::AccountIndex>;
 	type Target = T::AccountId;
-	fn lookup(a: Self::Source) -> result::Result<Self::Target, &'static str> {
-		Self::lookup_address(a).ok_or("invalid account index")
+
+	fn lookup(a: Self::Source) -> Result<T::AccountId, LookupError> {
+		Self::lookup_address(a).ok_or(LookupError)
 	}
+
 	fn unlookup(a: Self::Target) -> Self::Source {
 		address::Address::Id(a)
 	}

substrate/srml/staking/src/lib.rs

@@ -882,8 +882,8 @@ decl_module! {
 			ensure!(!targets.is_empty(), "targets cannot be empty");
 			let targets = targets.into_iter()
 				.take(MAX_NOMINATIONS)
-				.map(T::Lookup::lookup)
-				.collect::<result::Result<Vec<T::AccountId>, &'static str>>()?;
+				.map(|t| T::Lookup::lookup(t))
+				.collect::<result::Result<Vec<T::AccountId>, _>>()?;
 
 			<Validators<T>>::remove(stash);
 			<Nominators<T>>::insert(stash, targets);

substrate/srml/staking/src/tests.rs

@@ -748,7 +748,10 @@ fn cannot_transfer_staked_balance() {
 		// Confirm account 11 (via controller 10) is totally staked
 		assert_eq!(Staking::stakers(&11).total, 1000);
 		// Confirm account 11 cannot transfer as a result
-		assert_noop!(Balances::transfer(Origin::signed(11), 20, 1), "account liquidity restrictions prevent withdrawal");
+		assert_noop!(
+			Balances::transfer(Origin::signed(11), 20, 1),
+			"account liquidity restrictions prevent withdrawal",
+		);
 
 		// Give account 11 extra free balance
 		let _ = Balances::make_free_balance_be(&11, 10000);
@@ -774,7 +777,10 @@ fn cannot_transfer_staked_balance_2() {
 		// Confirm account 21 (via controller 20) is totally staked
 		assert_eq!(Staking::stakers(&21).total, 1000);
 		// Confirm account 21 can transfer at most 1000
-		assert_noop!(Balances::transfer(Origin::signed(21), 20, 1001), "account liquidity restrictions prevent withdrawal");
+		assert_noop!(
+			Balances::transfer(Origin::signed(21), 20, 1001),
+			"account liquidity restrictions prevent withdrawal",
+		);
 		assert_ok!(Balances::transfer(Origin::signed(21), 20, 1000));
 	});
 }

substrate/srml/sudo/src/lib.rs

@@ -87,12 +87,10 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use rstd::prelude::*;
-use sr_primitives::traits::StaticLookup;
-use sr_primitives::weights::SimpleDispatchInfo;
-use support::{
-	StorageValue, Parameter, Dispatchable, decl_module, decl_event,
-	decl_storage, ensure
+use sr_primitives::{
+	traits::{StaticLookup, Dispatchable}, weights::SimpleDispatchInfo, DispatchError,
 };
+use support::{StorageValue, Parameter, decl_module, decl_event, decl_storage, ensure};
 use system::ensure_signed;
 
 pub trait Trait: system::Trait {
@@ -126,6 +124,7 @@ decl_module! {
 			let res = match proposal.dispatch(system::RawOrigin::Root.into()) {
 				Ok(_) => true,
 				Err(e) => {
+					let e: DispatchError = e.into();
 					runtime_io::print(e);
 					false
 				}

substrate/srml/support/src/dispatch.rs

@@ -25,18 +25,18 @@ pub use srml_metadata::{
 	FunctionMetadata, DecodeDifferent, DecodeDifferentArray, FunctionArgumentMetadata,
 	ModuleConstantMetadata, DefaultByte, DefaultByteGetter,
 };
-pub use sr_primitives::weights::{SimpleDispatchInfo, GetDispatchInfo, DispatchInfo, WeighData,
-	ClassifyDispatch,
-	TransactionPriority
+pub use sr_primitives::{
+	weights::{
+		SimpleDispatchInfo, GetDispatchInfo, DispatchInfo, WeighData, ClassifyDispatch,
+		TransactionPriority
+	}, traits::{Dispatchable, DispatchResult, ModuleDispatchError}, DispatchError
 };
-pub use sr_primitives::traits::{Dispatchable, DispatchResult};
 
 /// A type that cannot be instantiated.
 pub enum Never {}
 
-/// Result of a module function call; either nothing (functions are only called for "side effects")
-/// or an error message.
-pub type Result = DispatchResult;
+/// Result with string error message. This exists for backward compatibility purpose.
+pub type Result = DispatchResult<&'static str>;
 
 /// Serializable version of Dispatchable.
 /// This value can be used as a "function" in an extrinsic.
@@ -239,6 +239,7 @@ macro_rules! decl_module {
 			{}
 			{}
 			{}
+			{}
 			[]
 			$($t)*
 		);
@@ -270,6 +271,7 @@ macro_rules! decl_module {
 			{}
 			{}
 			{}
+			{}
 			[]
 			$($t)*
 		);
@@ -286,6 +288,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		$vis:vis fn deposit_event() = default;
@@ -301,6 +304,7 @@ macro_rules! decl_module {
 			{ $( $on_finalize )* }
 			{ $( $offchain )* }
 			{ $( $constants )* }
+			{ $( $error_type )* }
 			[ $( $dispatchables )* ]
 			$($rest)*
 		);
@@ -315,6 +319,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		$vis:vis fn deposit_event
@@ -334,6 +339,7 @@ macro_rules! decl_module {
 		{}
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		fn on_finalize($($param_name:ident : $param:ty),* ) { $( $impl:tt )* }
@@ -349,6 +355,7 @@ macro_rules! decl_module {
 			{ fn on_finalize( $( $param_name : $param ),* ) { $( $impl )* } }
 			{ $( $offchain )* }
 			{ $( $constants )* }
+			{ $( $error_type )* }
 			[ $( $dispatchables )* ]
 			$($rest)*
 		);
@@ -363,6 +370,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		fn on_initialize($($param_name:ident : $param:ty),* ) { $( $impl:tt )* }
@@ -378,6 +386,7 @@ macro_rules! decl_module {
 			{ $( $on_finalize )* }
 			{ $( $offchain )* }
 			{ $( $constants )* }
+			{ $( $error_type )* }
 			[ $( $dispatchables )* ]
 			$($rest)*
 		);
@@ -395,6 +404,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		fn offchain_worker($($param_name:ident : $param:ty),* ) { $( $impl:tt )* }
@@ -412,6 +422,7 @@ macro_rules! decl_module {
 			{ $( $on_finalize )* }
 			{ fn offchain_worker( $( $param_name : $param ),* ) { $( $impl )* } }
 			{ $( $constants )* }
+			{ $( $error_type )* }
 			[ $( $dispatchables )* ]
 			$($rest)*
 		);
@@ -431,6 +442,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$( #[doc = $doc_attr:tt] )*
 		const $name:ident: $ty:ty = $value:expr;
@@ -453,11 +465,85 @@ macro_rules! decl_module {
 				$( #[doc = $doc_attr ] )*
 				$name: $ty = $value;
 			}
+			{ $( $error_type )* }
 			[ $( $dispatchables )* ]
 			$($rest)*
 		);
 	};
 
+	// Parse error type
+	(@normalize
+		$(#[$attr:meta])*
+		pub struct $mod_type:ident<
+			$trait_instance:ident:
+				$trait_name:ident$(<I>, $instance:ident: $instantiable:path $(= $module_default_instance:path)?)?
+			>
+		for enum $call_type:ident where origin: $origin_type:ty, system = $system:ident
+		{ $( $other_where_bounds:tt )* }
+		{ $( $deposit_event:tt )* }
+		{ $( $on_initialize:tt )* }
+		{ $( $on_finalize:tt )* }
+		{ $( $offchain:tt )* }
+		{ $( $constants:tt )* }
+		{ }
+		[ $( $dispatchables:tt )* ]
+		$(#[doc = $doc_attr:tt])*
+		type Error = $error_type:ty;
+		$($rest:tt)*
+	) => {
+		$crate::decl_module!(@normalize
+			$(#[$attr])*
+			pub struct $mod_type<
+				$trait_instance: $trait_name$(<I>, $instance: $instantiable $(= $module_default_instance)?)?
+			>
+			for enum $call_type where origin: $origin_type, system = $system
+			{ $( $other_where_bounds )* }
+			{ $( $deposit_event )* }
+			{ $( $on_initialize )* }
+			{ $( $on_finalize )* }
+			{ $( $offchain )* }
+			{ $( $constants )* }
+			{ $error_type }
+			[ $( $dispatchables )* ]
+			$($rest)*
+		);
+	};
+	// Add default Error if none supplied
+	(@normalize
+		$(#[$attr:meta])*
+		pub struct $mod_type:ident<
+			$trait_instance:ident:
+				$trait_name:ident$(<I>, $instance:ident: $instantiable:path $(= $module_default_instance:path)?)?
+			>
+		for enum $call_type:ident where origin: $origin_type:ty, system = $system:ident
+		{ $( $other_where_bounds:tt )* }
+		{ $( $deposit_event:tt )* }
+		{ $( $on_initialize:tt )* }
+		{ $( $on_finalize:tt )* }
+		{ $( $offchain:tt )* }
+		{ $( $constants:tt )* }
+		{ }
+		[ $($t:tt)* ]
+		$($rest:tt)*
+	) => {
+		$crate::decl_module!(@normalize
+			$(#[$attr])*
+			pub struct $mod_type<
+				$trait_instance: $trait_name$(<I>, $instance: $instantiable $(= $module_default_instance)?)?
+			>
+			for enum $call_type where origin: $origin_type, system = $system
+			{ $( $other_where_bounds )* }
+			{ $( $deposit_event )* }
+			{ $( $on_initialize )* }
+			{ $( $on_finalize )* }
+			{ $( $offchain )* }
+			{ $( $constants )* }
+			{ &'static str }
+			[ $($t)* ]
+			$($rest)*
+		);
+	};
+
 	// This puts the function statement into the [], decreasing `$rest` and moving toward finishing the parse.
 	(@normalize
 		$(#[$attr:meta])*
@@ -472,6 +558,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $error_type:ty }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		#[weight = $weight:expr]
@@ -492,6 +579,7 @@ macro_rules! decl_module {
 			{ $( $on_finalize )* }
 			{ $( $offchain )* }
 			{ $( $constants )* }
+			{ $error_type }
 			[
 				$( $dispatchables )*
 				$(#[doc = $doc_attr])*
@@ -518,6 +606,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		$fn_vis:vis fn $fn_name:ident(
@@ -537,6 +626,7 @@ macro_rules! decl_module {
 			{ $( $on_finalize )* }
 			{ $( $offchain )* }
 			{ $( $constants )* }
+			{ $( $error_type )* }
 			[ $( $dispatchables )* ]
 			$(#[doc = $doc_attr])*
 			#[weight = $crate::dispatch::SimpleDispatchInfo::default()]
@@ -557,6 +647,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		$(#[weight = $weight:expr])?
@@ -581,6 +672,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		$(#[weight = $weight:expr])?
@@ -605,6 +697,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 		$(#[doc = $doc_attr:tt])*
 		$(#[weight = $weight:expr])?
@@ -630,6 +723,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $( $error_type:tt )* }
 		[ $( $dispatchables:tt )* ]
 	) => {
 		$crate::decl_module!(@imp
@@ -644,6 +738,7 @@ macro_rules! decl_module {
 			{ $( $on_finalize )* }
 			{ $( $offchain )* }
 			{ $( $constants )* }
+			{ $( $error_type )* }
 		);
 	};
 
@@ -794,6 +889,7 @@ macro_rules! decl_module {
 	(@impl_function
 		$module:ident<$trait_instance:ident: $trait_name:ident$(<I>, $instance:ident: $instantiable:path)?>;
 		$origin_ty:ty;
+		$error_type:ty;
 		$ignore:ident;
 		$(#[doc = $doc_attr:tt])*
 		$vis:vis fn $name:ident (
@@ -804,7 +900,7 @@ macro_rules! decl_module {
 		#[allow(unreachable_code)]
 		$vis fn $name(
 			$origin: $origin_ty $(, $param: $param_ty )*
-		) -> $crate::dispatch::Result {
+		) -> $crate::dispatch::DispatchResult<$error_type> {
 			{ $( $impl )* }
 			// May be unreachable.
 			Ok(())
@@ -815,6 +911,7 @@ macro_rules! decl_module {
 	(@impl_function
 		$module:ident<$trait_instance:ident: $trait_name:ident$(<I>, $instance:ident: $instantiable:path)?>;
 		$origin_ty:ty;
+		$error_type:ty;
 		$ignore:ident;
 		$(#[doc = $doc_attr:tt])*
 		$vis:vis fn $name:ident (
@@ -969,6 +1066,7 @@ macro_rules! decl_module {
 		{ $( $on_finalize:tt )* }
 		{ $( $offchain:tt )* }
 		{ $( $constants:tt )* }
+		{ $error_type:ty }
 	) => {
 		$crate::__check_reserved_fn_name! { $( $fn_name )* }
 
@@ -1020,6 +1118,7 @@ macro_rules! decl_module {
 					@impl_function
 					$mod_type<$trait_instance: $trait_name $(<I>, $fn_instance: $fn_instantiable)?>;
 					$origin_type;
+					$error_type;
 					$from;
 					$(#[doc = $doc_attr])*
 					$fn_vis fn $fn_name (
@@ -1150,7 +1249,8 @@ macro_rules! decl_module {
 		{
 			type Trait = $trait_instance;
 			type Origin = $origin_type;
-			fn dispatch(self, _origin: Self::Origin) -> $crate::dispatch::Result {
+			type Error = $error_type;
+			fn dispatch(self, _origin: Self::Origin) -> $crate::dispatch::DispatchResult<Self::Error> {
 				match self {
 					$(
 						$call_type::$fn_name( $( $param_name ),* ) => {
@@ -1177,8 +1277,8 @@ macro_rules! decl_module {
 			#[doc(hidden)]
 			pub fn dispatch<D: $crate::dispatch::Dispatchable<Trait = $trait_instance>>(
 				d: D,
-				origin: D::Origin,
-			) -> $crate::dispatch::Result {
+				origin: D::Origin
+			) -> $crate::dispatch::DispatchResult<D::Error> {
 				d.dispatch(origin)
 			}
 		}
@@ -1234,9 +1334,19 @@ macro_rules! impl_outer_dispatch {
 		impl $crate::dispatch::Dispatchable for $call_type {
 			type Origin = $origin;
 			type Trait = $call_type;
-			fn dispatch(self, origin: $origin) -> $crate::dispatch::Result {
-				match self {
-					$( $call_type::$camelcase(call) => call.dispatch(origin), )*
+			type Error = $crate::dispatch::DispatchError;
+			fn dispatch(
+				self,
+				origin: $origin,
+			) -> $crate::dispatch::DispatchResult<$crate::dispatch::DispatchError> {
+				$crate::impl_outer_dispatch! {
+					@DISPATCH_MATCH
+					self
+					$call_type
+					origin
+					{}
+					0;
+					$( $camelcase ),*
 				}
 			}
 		}
@@ -1258,6 +1368,43 @@ macro_rules! impl_outer_dispatch {
 				}
 			}
 		)*
+	};
+	(@DISPATCH_MATCH
+		$self:ident
+		$call_type:ident
+		$origin:ident
+		{ $( $generated:tt )* }
+		$index:expr;
+		$name:ident
+		$( , $rest:ident )*
+	) => {
+		$crate::impl_outer_dispatch! {
+			@DISPATCH_MATCH
+			$self
+			$call_type
+			$origin
+			{
+				$( $generated )*
+				$call_type::$name(call) => call.dispatch($origin).map_err(|e| {
+					let mut error: $crate::dispatch::DispatchError = e.into();
+					error.module = Some($index);
+					error
+				}),
+			}
+			$index + 1;
+			$( $rest ),*
+		}
+	};
+	(@DISPATCH_MATCH
+		$self:ident
+		$call_type:ident
+		$origin:ident
+		{ $( $generated:tt )* }
+		$index:expr;
+	) => {
+		match $self {
+			$( $generated )*
+		}
 	}
 }
 

substrate/srml/support/src/error.rs

@@ -0,0 +1,151 @@
+// 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/>.
+
+//! Macro for declaring a module error.
+
+#[doc(hidden)]
+pub use sr_primitives::traits::LookupError;
+
+/// Declare an error type for a runtime module.
+///
+/// The generated error type inherently has the variants `Other` and `CannotLookup`. `Other` can
+/// hold any `&'static str` error message and is present for convenience/backward compatibility.
+/// The `CannotLookup` variant indicates that some lookup could not be done. For both variants the
+/// error type implements `From<&'static str>` and `From<LookupError>` to make them usable with the
+/// try operator.
+///
+/// # Usage
+///
+/// ```
+/// # use srml_support::decl_error;
+/// decl_error! {
+///     /// Errors that can occur in my module.
+///     pub enum MyError {
+///         /// Hey this is an error message that indicates bla.
+///         MyCoolErrorMessage,
+///         /// You are just not cool enough for my module!
+///         YouAreNotCoolEnough,
+///     }
+/// }
+/// ```
+///
+/// `decl_error!` supports only variants that do not hold any data.
+#[macro_export]
+macro_rules! decl_error {
+	(
+		$(#[$attr:meta])*
+		pub enum $error:ident {
+			$(
+				$( #[$variant_attr:meta] )*
+				$name:ident
+			),*
+			$(,)?
+		}
+	) => {
+		#[derive(Clone, PartialEq, Eq)]
+		#[cfg_attr(feature = "std", derive(Debug))]
+		$(#[$attr])*
+		pub enum $error {
+			Other(&'static str),
+			CannotLookup,
+			$(
+				$(#[$variant_attr])*
+				$name
+			),*
+		}
+
+		impl $crate::dispatch::ModuleDispatchError for $error {
+			fn as_u8(&self) -> u8 {
+				$crate::decl_error! {
+					@GENERATE_AS_U8
+					self
+					$error
+					{}
+					2,
+					$( $name ),*
+				}
+			}
+
+			fn as_str(&self) -> &'static str {
+				match self {
+					$error::Other(err) => err,
+					$error::CannotLookup => "Can not lookup",
+					$(
+						$error::$name => stringify!($name),
+					)*
+				}
+			}
+		}
+
+		impl From<&'static str> for $error {
+			fn from(val: &'static str) -> $error {
+				$error::Other(val)
+			}
+		}
+
+		impl From<$crate::error::LookupError> for $error {
+			fn from(_: $crate::error::LookupError) -> $error {
+				$error::CannotLookup
+			}
+		}
+
+		impl From<$error> for &'static str {
+			fn from(err: $error) -> &'static str {
+				use $crate::dispatch::ModuleDispatchError;
+				err.as_str()
+			}
+		}
+
+		impl Into<$crate::dispatch::DispatchError> for $error {
+			fn into(self) -> $crate::dispatch::DispatchError {
+				use $crate::dispatch::ModuleDispatchError;
+				$crate::dispatch::DispatchError::new(None, self.as_u8(), Some(self.as_str()))
+			}
+		}
+	};
+	(@GENERATE_AS_U8
+		$self:ident
+		$error:ident
+		{ $( $generated:tt )* }
+		$index:expr,
+		$name:ident
+		$( , $rest:ident )*
+	) => {
+		$crate::decl_error! {
+			@GENERATE_AS_U8
+			$self
+			$error
+			{
+				$( $generated )*
+				$error::$name => $index,
+			}
+			$index + 1,
+			$( $rest ),*
+		}
+	};
+	(@GENERATE_AS_U8
+		$self:ident
+		$error:ident
+		{ $( $generated:tt )* }
+		$index:expr,
+	) => {
+		match $self {
+			$error::Other(_) => 0,
+			$error::CannotLookup => 1,
+			$( $generated )*
+		}
+	}
+}

substrate/srml/support/src/lib.rs

@@ -58,14 +58,16 @@ mod runtime;
 pub mod inherent;
 #[macro_use]
 pub mod unsigned;
+#[macro_use]
+pub mod error;
 mod double_map;
 pub mod traits;
 
 pub use self::storage::{StorageValue, StorageMap, StorageLinkedMap, StorageDoubleMap};
 pub use self::hashable::Hashable;
-pub use self::dispatch::{Parameter, Dispatchable, Callable, IsSubType};
+pub use self::dispatch::{Parameter, Callable, IsSubType};
 pub use self::double_map::StorageDoubleMapWithHasher;
-pub use runtime_io::{print, storage_root};
+pub use runtime_io::{print, storage_root, Printable};
 pub use sr_primitives::{self, ConsensusEngineId};
 
 /// Macro for easily creating a new implementation of the `Get` trait. Use similarly to
@@ -128,7 +130,7 @@ macro_rules! fail {
 /// Used as `ensure!(expression_to_ensure, expression_to_return_on_false)`.
 #[macro_export]
 macro_rules! ensure {
-	( $x:expr, $y:expr ) => {{
+	( $x:expr, $y:expr $(,)? ) => {{
 		if !$x {
 			$crate::fail!($y);
 		}
@@ -142,7 +144,10 @@ macro_rules! ensure {
 #[macro_export]
 #[cfg(feature = "std")]
 macro_rules! assert_noop {
-	( $x:expr , $y:expr ) => {
+	(
+		$x:expr,
+		$y:expr $(,)?
+	) => {
 		let h = $crate::storage_root();
 		$crate::assert_err!($x, $y);
 		assert_eq!(h, $crate::storage_root());
@@ -159,7 +164,7 @@ macro_rules! assert_noop {
 #[macro_export]
 #[cfg(feature = "std")]
 macro_rules! assert_err {
-	( $x:expr , $y:expr ) => {
+	( $x:expr , $y:expr $(,)? ) => {
 		assert_eq!($x, Err($y));
 	}
 }

substrate/srml/support/src/unsigned.rs

@@ -17,7 +17,7 @@
 #[doc(hidden)]
 pub use crate::sr_primitives::traits::ValidateUnsigned;
 #[doc(hidden)]
-pub use crate::sr_primitives::transaction_validity::TransactionValidity;
+pub use crate::sr_primitives::transaction_validity::{TransactionValidity, UnknownTransaction};
 #[doc(hidden)]
 pub use crate::sr_primitives::ApplyError;
 
@@ -72,7 +72,7 @@ macro_rules! impl_outer_validate_unsigned {
 				#[allow(unreachable_patterns)]
 				match call {
 					$( Call::$module(inner_call) => $module::validate_unsigned(inner_call), )*
-					_ => $crate::unsigned::TransactionValidity::Invalid($crate::unsigned::ApplyError::BadSignature as i8),
+					_ => $crate::unsigned::UnknownTransaction::NoUnsignedValidator.into(),
 				}
 			}
 		}
@@ -81,8 +81,7 @@ macro_rules! impl_outer_validate_unsigned {
 
 #[cfg(test)]
 mod test_empty_call {
-	pub enum Call {
-	}
+	pub enum Call {}
 
 	#[allow(unused)]
 	pub struct Runtime;

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

@@ -27,6 +27,13 @@ support::decl_event!(
 	}
 );
 
+support::decl_error! {
+	pub enum Error {
+		TestError,
+		AnotherError
+	}
+}
+
 /// Origin for the system module.
 #[derive(PartialEq, Eq, Clone)]
 #[cfg_attr(feature = "std", derive(Debug))]

substrate/srml/system/src/lib.rs

@@ -95,22 +95,24 @@ use rstd::prelude::*;
 use rstd::map;
 use rstd::marker::PhantomData;
 use sr_version::RuntimeVersion;
-use sr_primitives::generic::{self, Era};
-use sr_primitives::Perbill;
-use sr_primitives::weights::{
-	Weight, DispatchInfo, DispatchClass, WeightMultiplier, SimpleDispatchInfo
-};
-use sr_primitives::transaction_validity::{
-	ValidTransaction, TransactionPriority, TransactionLongevity
-};
-use sr_primitives::traits::{self, CheckEqual, SimpleArithmetic, Zero, SignedExtension, Convert,
-	SimpleBitOps, Hash, Member, MaybeDisplay, EnsureOrigin, DispatchError, SaturatedConversion,
-	MaybeSerializeDebugButNotDeserialize, MaybeSerializeDebug, StaticLookup, One, Bounded, Lookup,
+use sr_primitives::{
+	generic::{self, Era}, Perbill, ApplyError, ApplyOutcome, DispatchError,
+	weights::{Weight, DispatchInfo, DispatchClass, WeightMultiplier, SimpleDispatchInfo},
+	transaction_validity::{
+		ValidTransaction, TransactionPriority, TransactionLongevity, TransactionValidityError,
+		InvalidTransaction, TransactionValidity,
+	},
+	traits::{
+		self, CheckEqual, SimpleArithmetic, Zero, SignedExtension, Convert, Lookup, LookupError,
+		SimpleBitOps, Hash, Member, MaybeDisplay, EnsureOrigin, SaturatedConversion,
+		MaybeSerializeDebugButNotDeserialize, MaybeSerializeDebug, StaticLookup, One, Bounded,
+	},
 };
+
 use primitives::storage::well_known_keys;
 use support::{
 	storage, decl_module, decl_event, decl_storage, StorageDoubleMap, StorageValue, StorageMap,
-	Parameter, for_each_tuple, traits::{Contains, Get}
+	Parameter, for_each_tuple, traits::{Contains, Get}, decl_error,
 };
 use safe_mix::TripletMix;
 use codec::{Encode, Decode};
@@ -248,6 +250,8 @@ pub type KeyValue = (Vec<u8>, Vec<u8>);
 
 decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		type Error = Error;
+
 		/// A big dispatch that will disallow any other transaction to be included.
 		// TODO: this must be preferable available for testing really (not possible at the moment).
 		#[weight = SimpleDispatchInfo::MaxOperational]
@@ -323,10 +327,21 @@ decl_event!(
 		/// An extrinsic completed successfully.
 		ExtrinsicSuccess,
 		/// An extrinsic failed.
-		ExtrinsicFailed,
+		ExtrinsicFailed(DispatchError),
 	}
 );
 
+decl_error! {
+	/// Error for the System module
+	pub enum Error {
+		BadSignature,
+		BlockFull,
+		RequireSignedOrigin,
+		RequireRootOrigin,
+		RequireNoOrigin,
+	}
+}
+
 /// Origin for the System module.
 #[derive(PartialEq, Eq, Clone)]
 #[cfg_attr(feature = "std", derive(Debug))]
@@ -510,32 +525,32 @@ impl<O, T> EnsureOrigin<O> for EnsureNever<T> {
 
 /// Ensure that the origin `o` represents a signed extrinsic (i.e. transaction).
 /// Returns `Ok` with the account that signed the extrinsic or an `Err` otherwise.
-pub fn ensure_signed<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<AccountId, &'static str>
+pub fn ensure_signed<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<AccountId, Error>
 	where OuterOrigin: Into<Result<RawOrigin<AccountId>, OuterOrigin>>
 {
 	match o.into() {
 		Ok(RawOrigin::Signed(t)) => Ok(t),
-		_ => Err("bad origin: expected to be a signed origin"),
+		_ => Err(Error::RequireSignedOrigin),
 	}
 }
 
 /// Ensure that the origin `o` represents the root. Returns `Ok` or an `Err` otherwise.
-pub fn ensure_root<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), &'static str>
+pub fn ensure_root<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), Error>
 	where OuterOrigin: Into<Result<RawOrigin<AccountId>, OuterOrigin>>
 {
 	match o.into() {
 		Ok(RawOrigin::Root) => Ok(()),
-		_ => Err("bad origin: expected to be a root origin"),
+		_ => Err(Error::RequireRootOrigin),
 	}
 }
 
 /// Ensure that the origin `o` represents an unsigned extrinsic. Returns `Ok` or an `Err` otherwise.
-pub fn ensure_none<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), &'static str>
+pub fn ensure_none<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), Error>
 	where OuterOrigin: Into<Result<RawOrigin<AccountId>, OuterOrigin>>
 {
 	match o.into() {
 		Ok(RawOrigin::None) => Ok(()),
-		_ => Err("bad origin: expected to be no origin"),
+		_ => Err(Error::RequireNoOrigin),
 	}
 }
 
@@ -811,11 +826,13 @@ impl<T: Trait> Module<T> {
 	}
 
 	/// To be called immediately after an extrinsic has been applied.
-	pub fn note_applied_extrinsic(r: &Result<(), &'static str>, _encoded_len: u32) {
-		Self::deposit_event(match r {
-			Ok(_) => Event::ExtrinsicSuccess,
-			Err(_) => Event::ExtrinsicFailed,
-		});
+	pub fn note_applied_extrinsic(r: &ApplyOutcome, _encoded_len: u32) {
+		Self::deposit_event(
+			match r {
+				Ok(()) => Event::ExtrinsicSuccess,
+				Err(err) => Event::ExtrinsicFailed(err.clone()),
+			}
+		);
 
 		let next_extrinsic_index = Self::extrinsic_index().unwrap_or_default() + 1u32;
 
@@ -844,7 +861,6 @@ impl<T: Trait> Module<T> {
 pub struct CheckWeight<T: Trait + Send + Sync>(PhantomData<T>);
 
 impl<T: Trait + Send + Sync> CheckWeight<T> {
-
 	/// Get the quota ratio of each dispatch class type. This indicates that all operational
 	/// dispatches can use the full capacity of any resource, while user-triggered ones can consume
 	/// a portion.
@@ -859,31 +875,33 @@ impl<T: Trait + Send + Sync> CheckWeight<T> {
 	/// Checks if the current extrinsic can fit into the block with respect to block weight limits.
 	///
 	/// Upon successes, it returns the new block weight as a `Result`.
-	fn check_weight(info: DispatchInfo) -> Result<Weight, DispatchError> {
+	fn check_weight(info: DispatchInfo) -> Result<Weight, TransactionValidityError> {
 		let current_weight = Module::<T>::all_extrinsics_weight();
 		let maximum_weight = T::MaximumBlockWeight::get();
 		let limit = Self::get_dispatch_limit_ratio(info.class) * maximum_weight;
 		let added_weight = info.weight.min(limit);
 		let next_weight = current_weight.saturating_add(added_weight);
 		if next_weight > limit {
-			return Err(DispatchError::Exhausted)
+			Err(InvalidTransaction::ExhaustsResources.into())
+		} else {
+			Ok(next_weight)
 		}
-		Ok(next_weight)
 	}
 
 	/// Checks if the current extrinsic can fit into the block with respect to block length limits.
 	///
 	/// Upon successes, it returns the new block length as a `Result`.
-	fn check_block_length(info: DispatchInfo, len: usize) -> Result<u32, DispatchError> {
+	fn check_block_length(info: DispatchInfo, len: usize) -> Result<u32, TransactionValidityError> {
 		let current_len = Module::<T>::all_extrinsics_len();
 		let maximum_len = T::MaximumBlockLength::get();
 		let limit = Self::get_dispatch_limit_ratio(info.class) * maximum_len;
 		let added_len = len as u32;
 		let next_len = current_len.saturating_add(added_len);
 		if next_len > limit {
-			return Err(DispatchError::Exhausted)
+			Err(InvalidTransaction::ExhaustsResources.into())
+		} else {
+			Ok(next_len)
 		}
-		Ok(next_len)
 	}
 
 	/// get the priority of an extrinsic denoted by `info`.
@@ -906,7 +924,7 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckWeight<T> {
 	type AdditionalSigned = ();
 	type Pre = ();
 
-	fn additional_signed(&self) -> rstd::result::Result<(), &'static str> { Ok(()) }
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
 
 	fn pre_dispatch(
 		self,
@@ -914,7 +932,7 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckWeight<T> {
 		_call: &Self::Call,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<(), DispatchError> {
+	) -> Result<(), ApplyError> {
 		let next_len = Self::check_block_length(info, len)?;
 		AllExtrinsicsLen::put(next_len);
 		let next_weight = Self::check_weight(info)?;
@@ -928,12 +946,18 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckWeight<T> {
 		_call: &Self::Call,
 		info: DispatchInfo,
 		len: usize,
-	) -> Result<ValidTransaction, DispatchError> {
+	) -> TransactionValidity {
 		// There is no point in writing to storage here since changes are discarded. This basically
-		// discards any transaction which is bigger than the length or weight limit **alone**,which
+		// discards any transaction which is bigger than the length or weight limit **alone**, which
 		// is a guarantee that it will fail in the pre-dispatch phase.
-		let _ = Self::check_block_length(info, len)?;
-		let _ = Self::check_weight(info)?;
+		if let Err(e) = Self::check_block_length(info, len) {
+			return Err(e);
+		}
+
+		if let Err(e) = Self::check_weight(info) {
+			return Err(e);
+		}
+
 		Ok(ValidTransaction { priority: Self::get_priority(info), ..Default::default() })
 	}
 }
@@ -969,7 +993,7 @@ impl<T: Trait> SignedExtension for CheckNonce<T> {
 	type AdditionalSigned = ();
 	type Pre = ();
 
-	fn additional_signed(&self) -> rstd::result::Result<(), &'static str> { Ok(()) }
+	fn additional_signed(&self) -> rstd::result::Result<(), TransactionValidityError> { Ok(()) }
 
 	fn pre_dispatch(
 		self,
@@ -977,13 +1001,18 @@ impl<T: Trait> SignedExtension for CheckNonce<T> {
 		_call: &Self::Call,
 		_info: DispatchInfo,
 		_len: usize,
-	) -> Result<(), DispatchError> {
+	) -> Result<(), ApplyError> {
 		let expected = <AccountNonce<T>>::get(who);
 		if self.0 != expected {
 			return Err(
-				if self.0 < expected { DispatchError::Stale } else { DispatchError::Future }
+				if self.0 < expected {
+					InvalidTransaction::Stale
+				} else {
+					InvalidTransaction::Future
+				}.into()
 			)
 		}
+
 		<AccountNonce<T>>::insert(who, expected + T::Index::one());
 		Ok(())
 	}
@@ -994,11 +1023,11 @@ impl<T: Trait> SignedExtension for CheckNonce<T> {
 		_call: &Self::Call,
 		info: DispatchInfo,
 		_len: usize,
-	) -> Result<ValidTransaction, DispatchError> {
+	) -> TransactionValidity {
 		// check index
 		let expected = <AccountNonce<T>>::get(who);
 		if self.0 < expected {
-			return Err(DispatchError::Stale)
+			return InvalidTransaction::Stale.into()
 		}
 
 		let provides = vec![Encode::encode(&(who, self.0))];
@@ -1048,7 +1077,7 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckEra<T> {
 		_call: &Self::Call,
 		_info: DispatchInfo,
 		_len: usize,
-	) -> Result<ValidTransaction, DispatchError> {
+	) -> TransactionValidity {
 		let current_u64 = <Module<T>>::block_number().saturated_into::<u64>();
 		let valid_till = (self.0).0.death(current_u64);
 		Ok(ValidTransaction {
@@ -1057,11 +1086,14 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckEra<T> {
 		})
 	}
 
-	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
+	fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError> {
 		let current_u64 = <Module<T>>::block_number().saturated_into::<u64>();
 		let n = (self.0).0.birth(current_u64).saturated_into::<T::BlockNumber>();
-		if !<BlockHash<T>>::exists(n) { Err("transaction birth block ancient")? }
-		Ok(<Module<T>>::block_hash(n))
+		if !<BlockHash<T>>::exists(n) {
+			Err(InvalidTransaction::AncientBirthBlock.into())
+		} else {
+			Ok(<Module<T>>::block_hash(n))
+		}
 	}
 }
 
@@ -1089,7 +1121,7 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckGenesis<T> {
 	type AdditionalSigned = T::Hash;
 	type Pre = ();
 
-	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
+	fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError> {
 		Ok(<Module<T>>::block_hash(T::BlockNumber::zero()))
 	}
 }
@@ -1118,7 +1150,7 @@ impl<T: Trait + Send + Sync> SignedExtension for CheckVersion<T> {
 	type AdditionalSigned = u32;
 	type Pre = ();
 
-	fn additional_signed(&self) -> Result<Self::AdditionalSigned, &'static str> {
+	fn additional_signed(&self) -> Result<Self::AdditionalSigned, TransactionValidityError> {
 		Ok(<Module<T>>::runtime_version().spec_version)
 	}
 }
@@ -1133,7 +1165,8 @@ impl<T> Default for ChainContext<T> {
 impl<T: Trait> Lookup for ChainContext<T> {
 	type Source = <T::Lookup as StaticLookup>::Source;
 	type Target = <T::Lookup as StaticLookup>::Target;
-	fn lookup(&self, s: Self::Source) -> rstd::result::Result<Self::Target, &'static str> {
+
+	fn lookup(&self, s: Self::Source) -> Result<Self::Target, LookupError> {
 		<T::Lookup as StaticLookup>::lookup(s)
 	}
 }
@@ -1143,10 +1176,10 @@ mod tests {
 	use super::*;
 	use runtime_io::with_externalities;
 	use primitives::H256;
-	use sr_primitives::{traits::{BlakeTwo256, IdentityLookup}, testing::Header};
+	use sr_primitives::{traits::{BlakeTwo256, IdentityLookup}, testing::Header, DispatchError};
 	use support::{impl_outer_origin, parameter_types};
 
-	impl_outer_origin!{
+	impl_outer_origin! {
 		pub enum Origin for Test where system = super {}
 	}
 
@@ -1183,7 +1216,7 @@ mod tests {
 		fn from(e: Event) -> u16 {
 			match e {
 				Event::ExtrinsicSuccess => 100,
-				Event::ExtrinsicFailed => 101,
+				Event::ExtrinsicFailed(_) => 101,
 			}
 		}
 	}
@@ -1232,16 +1265,19 @@ mod tests {
 			System::initialize(&2, &[0u8; 32].into(), &[0u8; 32].into(), &Default::default());
 			System::deposit_event(42u16);
 			System::note_applied_extrinsic(&Ok(()), 0);
-			System::note_applied_extrinsic(&Err(""), 0);
+			System::note_applied_extrinsic(&Err(DispatchError::new(Some(1), 2, None)), 0);
 			System::note_finished_extrinsics();
 			System::deposit_event(3u16);
 			System::finalize();
-			assert_eq!(System::events(), vec![
-				EventRecord { phase: Phase::ApplyExtrinsic(0), event: 42u16, topics: vec![] },
-				EventRecord { phase: Phase::ApplyExtrinsic(0), event: 100u16, topics: vec![] },
-				EventRecord { phase: Phase::ApplyExtrinsic(1), event: 101u16, topics: vec![] },
-				EventRecord { phase: Phase::Finalization, event: 3u16, topics: vec![] }
-			]);
+			assert_eq!(
+				System::events(),
+				vec![
+					EventRecord { phase: Phase::ApplyExtrinsic(0), event: 42u16, topics: vec![] },
+					EventRecord { phase: Phase::ApplyExtrinsic(0), event: 100u16, topics: vec![] },
+					EventRecord { phase: Phase::ApplyExtrinsic(1), event: 101u16, topics: vec![] },
+					EventRecord { phase: Phase::Finalization, event: 3u16, topics: vec![] }
+				]
+			);
 		});
 	}
 
@@ -1440,14 +1476,17 @@ mod tests {
 			let op = DispatchInfo { weight: 100, class: DispatchClass::Operational };
 			let len = 0_usize;
 
-			assert_eq!(
-				CheckWeight::<Test>(PhantomData).validate(&1, CALL, normal, len).unwrap().priority,
-				100,
-			);
-			assert_eq!(
-				CheckWeight::<Test>(PhantomData).validate(&1, CALL, op, len).unwrap().priority,
-				Bounded::max_value(),
-			);
+			let priority = CheckWeight::<Test>(PhantomData)
+				.validate(&1, CALL, normal, len)
+				.unwrap()
+				.priority;
+			assert_eq!(priority, 100);
+
+			let priority = CheckWeight::<Test>(PhantomData)
+				.validate(&1, CALL, op, len)
+				.unwrap()
+				.priority;
+			assert_eq!(priority, Bounded::max_value());
 		})
 	}
 
@@ -1481,7 +1520,7 @@ mod tests {
 			// future
 			assert_eq!(
 				CheckEra::<Test>::from(Era::mortal(4, 2)).additional_signed().err().unwrap(),
-				"transaction birth block ancient"
+				InvalidTransaction::AncientBirthBlock.into(),
 			);
 
 			// correct
@@ -1503,10 +1542,7 @@ mod tests {
 			System::set_block_number(17);
 			<BlockHash<Test>>::insert(16, H256::repeat_byte(1));
 
-			assert_eq!(
-				ext.validate(&1, CALL, normal, len).unwrap().longevity,
-				15,
-			);
+			assert_eq!(ext.validate(&1, CALL, normal, len).unwrap().longevity, 15);
 		})
 	}
 }

substrate/subkey/src/main.rs

@@ -103,6 +103,7 @@ fn execute<C: Crypto>(matches: clap::ArgMatches) where
 			system::CheckNonce::<Runtime>::from(i),
 			system::CheckWeight::<Runtime>::new(),
 			balances::TakeFees::<Runtime>::from(f),
+			Default::default(),
 		)
 	};
 	let password = matches.value_of("password");
@@ -185,7 +186,7 @@ fn execute<C: Crypto>(matches: clap::ArgMatches) where
 			let raw_payload = SignedPayload::from_raw(
 				function,
 				extra(index, 0),
-				(VERSION.spec_version as u32, genesis_hash, genesis_hash, (), (), ()),
+				(VERSION.spec_version as u32, genesis_hash, genesis_hash, (), (), (), ()),
 			);
 			let signature = raw_payload.using_encoded(|payload| {
 				println!("Signing {}", HexDisplay::from(&payload));