From 7937af9919e7520d0c49e8a11cdfb8f78d400953 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Thu, 5 Jul 2018 18:22:06 +0200
Subject: [PATCH 01/21] runtime: refactor Checkable and BlindCheckable traits

---
 substrate/runtime/primitives/src/traits.rs | 34 ++++++++++------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 218fbc12769f6..5f75ff3f3cf43 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -371,31 +371,29 @@ pub type HashingFor<B> = <<B as Block>::Header as Header>::Hashing;
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
-pub trait Checkable: Sized + Send + Sync {
-	type Address: Member + MaybeDisplay;
-	type AccountId: Member + MaybeDisplay;
-	type Checked: Member;
-	fn sender(&self) -> &Self::Address;
-	fn check<ThisLookup: FnOnce(Self::Address) -> Result<Self::AccountId, &'static str>>(self, lookup: ThisLookup) -> Result<Self::Checked, &'static str>;
+/// for things that can be checked by providing additional context `Ctx`
+pub trait Checkable<Ctx>: Sized {
+    type Checked;
+
+    fn check_with(self, ctx: Ctx) -> Result<Self::Checked, Self>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
-///
-/// This does that checking without requiring a lookup argument.
-pub trait BlindCheckable: Sized + Send + Sync {
-	type Address: Member + MaybeDisplay;
-	type Checked: Member;
-	fn sender(&self) -> &Self::Address;
-	fn check(self) -> Result<Self::Checked, &'static str>;
+/// for things that can be checked without additional context.
+pub trait BlindCheckable: Sized {
+    type Checked;
+
+    /// gives back in case of an error.
+    fn check(self) -> Result<Self::Checked, Self>;
 }
 
-impl<T: BlindCheckable> Checkable for T {
-	type Address = <Self as BlindCheckable>::Address;
-	type AccountId = <Self as BlindCheckable>::Address;
+// every BlindCheckable is also a Checkable for arbitrary context `Ctx`
+impl<T: BlindCheckable, Ctx> Checkable<Ctx> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
-	fn sender(&self) -> &Self::Address { BlindCheckable::sender(self) }
-	fn check<ThisLookup: FnOnce(Self::Address) -> Result<Self::AccountId, &'static str>>(self, _: ThisLookup) -> Result<Self::Checked, &'static str> { BlindCheckable::check(self) }
+	fn check_with(self, _: Ctx) -> Result<Self::Checked, Self> {
+        BlindCheckable::check(self)
+    }
 }
 
 /// An "executable" piece of information, used by the standard Substrate Executive in order to

From cf080b099fe6989749f7582df89b970217fc20d0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Thu, 5 Jul 2018 18:22:55 +0200
Subject: [PATCH 02/21] fix impl BlindCheckable for Extrinsic

---
 substrate/test-runtime/src/lib.rs | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/substrate/test-runtime/src/lib.rs b/substrate/test-runtime/src/lib.rs
index 1b07035e966e8..6f9da3a93d8ed 100644
--- a/substrate/test-runtime/src/lib.rs
+++ b/substrate/test-runtime/src/lib.rs
@@ -119,16 +119,12 @@ impl Slicable for Extrinsic {
 
 impl BlindCheckable for Extrinsic {
 	type Checked = Self;
-	type Address = AccountId;
 
-	fn sender(&self) -> &Self::Address {
-		&self.transfer.from
-	}
-	fn check(self) -> Result<Self, &'static str> {
+	fn check(self) -> Result<Self, Self> {
 		if ::runtime_primitives::verify_encoded_lazy(&self.signature, &self.transfer, &self.transfer.from) {
 			Ok(self)
 		} else {
-			Err("bad signature")
+			Err(self)
 		}
 	}
 }

From 0b2ff34f7bcad5fcd3d11c7f33773fa44a6146f5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Thu, 5 Jul 2018 18:23:18 +0200
Subject: [PATCH 03/21] fix impl Checkable for TestXt

---
 substrate/runtime/primitives/src/testing.rs | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/substrate/runtime/primitives/src/testing.rs b/substrate/runtime/primitives/src/testing.rs
index 7c712b40105e6..2b36ec8d057cf 100644
--- a/substrate/runtime/primitives/src/testing.rs
+++ b/substrate/runtime/primitives/src/testing.rs
@@ -157,12 +157,9 @@ impl<Call: AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + Deseri
 		self.0.encode()
 	}
 }
-impl<Call: 'static + AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug> Checkable for TestXt<Call> {
+impl<Call: 'static + AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug, Ctx> Checkable<Ctx> for TestXt<Call> {
 	type Checked = Self;
-	type Address = u64;
-	type AccountId = u64;
-	fn sender(&self) -> &u64 { &(self.0).0 }
-	fn check<ThisLookup: FnOnce(Self::Address) -> Result<Self::AccountId, &'static str>>(self, _lookup: ThisLookup) -> Result<Self::Checked, &'static str> { Ok(self) }
+	fn check_with(self, _: Ctx) -> Result<Self::Checked, Self> { Ok(self) }
 }
 impl<Call: AuxDispatchable<Aux = u64> + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug> Applyable for TestXt<Call> {
 	type AccountId = u64;

From d2771697cf26dbbf3a3194fa5df2475f6959db7d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Thu, 5 Jul 2018 18:28:02 +0200
Subject: [PATCH 04/21] fix impl Checkable for UncheckedExtrinsic

---
 substrate/runtime/primitives/src/generic.rs | 24 +++++++++------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/substrate/runtime/primitives/src/generic.rs b/substrate/runtime/primitives/src/generic.rs
index 6f8a46841c748..20b733f9c9897 100644
--- a/substrate/runtime/primitives/src/generic.rs
+++ b/substrate/runtime/primitives/src/generic.rs
@@ -96,7 +96,7 @@ impl<Address, AccountId, Index, Call, Signature> UncheckedExtrinsic<Address, Ind
 	}
 }
 
-impl<Address, AccountId, Index, Call, Signature> traits::Checkable
+impl<Address, AccountId, Index, Call, Signature, ThisLookup> traits::Checkable<ThisLookup>
 	for UncheckedExtrinsic<Address, Index, Call, ::MaybeUnsigned<Signature>>
 where
 	Address: Member + Default + MaybeDisplay,
@@ -106,18 +106,11 @@ where
 	AccountId: Member + Default + MaybeDisplay,
 	::MaybeUnsigned<Signature>: Member,
 	Extrinsic<AccountId, Index, Call>: Slicable,
+	ThisLookup: FnOnce(&Address) -> Result<AccountId, &'static str>,
 {
-	type Address = Address;
-	type AccountId = AccountId;
 	type Checked = CheckedExtrinsic<AccountId, Index, Call>;
 
-	fn sender(&self) -> &Address {
-		&self.extrinsic.signed
-	}
-
-	fn check<ThisLookup>(self, lookup: ThisLookup) -> Result<Self::Checked, &'static str> where
-		ThisLookup: FnOnce(Address) -> Result<AccountId, &'static str>,
-	{
+	fn check_with(self, lookup: ThisLookup) -> Result<Self::Checked, Self> {
 		if !self.is_signed() {
 			Ok(CheckedExtrinsic(Extrinsic {
 				signed: Default::default(),
@@ -127,14 +120,17 @@ where
 		} else {
 			let extrinsic: Extrinsic<AccountId, Index, Call>
 				= Extrinsic {
-					signed: lookup(self.extrinsic.signed)?,
-					index: self.extrinsic.index,
-					function: self.extrinsic.function,
+					signed: match lookup(&self.extrinsic.signed) {
+						Ok(x) => x,
+						Err(_) => return Err(self)
+					},
+					index: self.extrinsic.index.clone(),
+					function: self.extrinsic.function.clone(),
 				};
 			if ::verify_encoded_lazy(&self.signature, &extrinsic, &extrinsic.signed) {
 				Ok(CheckedExtrinsic(extrinsic))
 			} else {
-				Err("bad signature in extrinsic")
+				Err(self)
 			}
 		}
 	}

From 60a9e0c6b20190a8edb5db451ddd14bc139f48d0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Thu, 5 Jul 2018 18:28:37 +0200
Subject: [PATCH 05/21] fix tabs

---
 substrate/runtime/primitives/src/traits.rs | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 5f75ff3f3cf43..56a45a1556d08 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -373,27 +373,27 @@ pub type HashingFor<B> = <<B as Block>::Header as Header>::Hashing;
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
 /// for things that can be checked by providing additional context `Ctx`
 pub trait Checkable<Ctx>: Sized {
-    type Checked;
+	type Checked;
 
-    fn check_with(self, ctx: Ctx) -> Result<Self::Checked, Self>;
+	fn check_with(self, ctx: Ctx) -> Result<Self::Checked, Self>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
 /// for things that can be checked without additional context.
 pub trait BlindCheckable: Sized {
-    type Checked;
+	type Checked;
 
-    /// gives back in case of an error.
-    fn check(self) -> Result<Self::Checked, Self>;
+	/// gives back in case of an error.
+	fn check(self) -> Result<Self::Checked, Self>;
 }
 
 // every BlindCheckable is also a Checkable for arbitrary context `Ctx`
 impl<T: BlindCheckable, Ctx> Checkable<Ctx> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
 	fn check_with(self, _: Ctx) -> Result<Self::Checked, Self> {
-        BlindCheckable::check(self)
-    }
+		BlindCheckable::check(self)
+	}
 }
 
 /// An "executable" piece of information, used by the standard Substrate Executive in order to

From 02eb103015b833c995c9f9067aac2542bb7ce5ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:07:47 +0200
Subject: [PATCH 06/21] add ::Address to system::Trait since its no longer in
 Checkable trait

---
 demo/runtime/src/lib.rs                | 1 +
 polkadot/runtime/src/lib.rs            | 1 +
 polkadot/runtime/src/parachains.rs     | 1 +
 substrate/runtime/council/src/lib.rs   | 1 +
 substrate/runtime/democracy/src/lib.rs | 1 +
 substrate/runtime/executive/src/lib.rs | 1 +
 substrate/runtime/session/src/lib.rs   | 1 +
 substrate/runtime/staking/src/mock.rs  | 1 +
 substrate/runtime/system/src/lib.rs    | 1 +
 substrate/runtime/timestamp/src/lib.rs | 1 +
 10 files changed, 10 insertions(+)

diff --git a/demo/runtime/src/lib.rs b/demo/runtime/src/lib.rs
index 938bcbbfa2be3..f65d21e5868a7 100644
--- a/demo/runtime/src/lib.rs
+++ b/demo/runtime/src/lib.rs
@@ -89,6 +89,7 @@ impl system::Trait for Concrete {
 	type Hashing = BlakeTwo256;
 	type Digest = generic::Digest<Vec<u8>>;
 	type AccountId = AccountId;
+	type Address = Address;
 	type Header = generic::Header<BlockNumber, BlakeTwo256, Vec<u8>>;
 }
 
diff --git a/polkadot/runtime/src/lib.rs b/polkadot/runtime/src/lib.rs
index 532de07cd76ef..746607a932f39 100644
--- a/polkadot/runtime/src/lib.rs
+++ b/polkadot/runtime/src/lib.rs
@@ -132,6 +132,7 @@ impl system::Trait for Concrete {
 	type Hashing = BlakeTwo256;
 	type Digest = generic::Digest<Log>;
 	type AccountId = AccountId;
+	type Address = Address;
 	type Header = Header;
 }
 /// System module for this concrete runtime.
diff --git a/polkadot/runtime/src/parachains.rs b/polkadot/runtime/src/parachains.rs
index 3625633adf392..9486be6c92cc8 100644
--- a/polkadot/runtime/src/parachains.rs
+++ b/polkadot/runtime/src/parachains.rs
@@ -254,6 +254,7 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
+		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/council/src/lib.rs b/substrate/runtime/council/src/lib.rs
index a40a64b27b84f..52df49f3f100e 100644
--- a/substrate/runtime/council/src/lib.rs
+++ b/substrate/runtime/council/src/lib.rs
@@ -647,6 +647,7 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
+		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/democracy/src/lib.rs b/substrate/runtime/democracy/src/lib.rs
index c20d60d2de359..393a478b46ee9 100644
--- a/substrate/runtime/democracy/src/lib.rs
+++ b/substrate/runtime/democracy/src/lib.rs
@@ -389,6 +389,7 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
+		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index e5a8a1a19e29a..dcc68e5c73ea2 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -248,6 +248,7 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
+		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/session/src/lib.rs b/substrate/runtime/session/src/lib.rs
index 74debe5a84e24..7a301bd14bc39 100644
--- a/substrate/runtime/session/src/lib.rs
+++ b/substrate/runtime/session/src/lib.rs
@@ -283,6 +283,7 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
+		type Address = u64;
 		type Header = Header;
 	}
 	impl timestamp::Trait for Test {
diff --git a/substrate/runtime/staking/src/mock.rs b/substrate/runtime/staking/src/mock.rs
index c2cf48dbd19ab..254276a2a3322 100644
--- a/substrate/runtime/staking/src/mock.rs
+++ b/substrate/runtime/staking/src/mock.rs
@@ -43,6 +43,7 @@ impl system::Trait for Test {
 	type Hashing = ::primitives::traits::BlakeTwo256;
 	type Digest = Digest;
 	type AccountId = u64;
+	type Address = u64;
 	type Header = Header;
 }
 impl session::Trait for Test {
diff --git a/substrate/runtime/system/src/lib.rs b/substrate/runtime/system/src/lib.rs
index e5e0b47a29b9f..dce921f6d8f5f 100644
--- a/substrate/runtime/system/src/lib.rs
+++ b/substrate/runtime/system/src/lib.rs
@@ -69,6 +69,7 @@ pub trait Trait: Eq + Clone {
 	type Hashing: Hashing<Output = Self::Hash>;
 	type Digest: Parameter + Member + Default + traits::Digest;
 	type AccountId: Parameter + Member + MaybeDisplay + Ord + Default;
+	type Address: Parameter + Member + MaybeDisplay;
 	type Header: Parameter + traits::Header<
 		Number = Self::BlockNumber,
 		Hashing = Self::Hashing,
diff --git a/substrate/runtime/timestamp/src/lib.rs b/substrate/runtime/timestamp/src/lib.rs
index f541e0a11f30a..497bf6f06819f 100644
--- a/substrate/runtime/timestamp/src/lib.rs
+++ b/substrate/runtime/timestamp/src/lib.rs
@@ -158,6 +158,7 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
+		type Address = u64;
 		type Header = Header;
 	}
 	impl consensus::Trait for Test {

From b42b484a36efcd1a2e0d09ed7e48c393cb3013b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:08:22 +0200
Subject: [PATCH 07/21] replace tab by space in comment

---
 substrate/runtime/council/src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/substrate/runtime/council/src/lib.rs b/substrate/runtime/council/src/lib.rs
index 52df49f3f100e..6e955c712792a 100644
--- a/substrate/runtime/council/src/lib.rs
+++ b/substrate/runtime/council/src/lib.rs
@@ -549,7 +549,7 @@ impl<T: Trait> Module<T> {
 #[serde(rename_all = "camelCase")]
 #[serde(deny_unknown_fields)]
 pub struct GenesisConfig<T: Trait> {
-	// for the voting onto the  council
+	// for the voting onto the council
 	pub candidacy_bond: T::Balance,
 	pub voter_bond: T::Balance,
 	pub present_slash_per_voter: T::Balance,

From 05fe805185cb78427a6780568ec48d79b6c4adc2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:13:34 +0200
Subject: [PATCH 08/21] replace occurences of Checkable::check with
 ::check_with

---
 polkadot/runtime/src/utils.rs          | 2 +-
 polkadot/transaction-pool/src/lib.rs   | 2 +-
 substrate/runtime/executive/src/lib.rs | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/polkadot/runtime/src/utils.rs b/polkadot/runtime/src/utils.rs
index 4c16e215bab7e..1531590ff5fca 100644
--- a/polkadot/runtime/src/utils.rs
+++ b/polkadot/runtime/src/utils.rs
@@ -47,5 +47,5 @@ pub fn inherent_extrinsics(timestamp: ::primitives::Timestamp, parachain_heads:
 
 /// Checks an unchecked extrinsic for validity.
 pub fn check_extrinsic(xt: UncheckedExtrinsic) -> bool {
-	xt.check(Staking::lookup).is_ok()
+	xt.check_with(Staking::lookup).is_ok()
 }
diff --git a/polkadot/transaction-pool/src/lib.rs b/polkadot/transaction-pool/src/lib.rs
index 5f344035cec0a..e8ff48aa44fe4 100644
--- a/polkadot/transaction-pool/src/lib.rs
+++ b/polkadot/transaction-pool/src/lib.rs
@@ -281,7 +281,7 @@ impl<'a, A> txpool::Verifier<UncheckedExtrinsic> for Verifier<'a, A> where
 		}
 
 		let (encoded_size, hash) = uxt.using_encoded(|e| (e.len(), BlakeTwo256::hash(e)));
-		let inner = match uxt.clone().check(|a| self.lookup(a)) {
+		let inner = match uxt.clone().check_with(|a| self.lookup(a)) {
 			Ok(xt) => Some(xt),
 			// keep the transaction around in the future pool and attempt to promote it later.
 			Err(Self::NO_ACCOUNT) => None,
diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index dcc68e5c73ea2..9ccf3c77c80d3 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -172,7 +172,7 @@ impl<
 	/// Actually apply an extrinsic given its `encoded_len`; this doesn't note its hash.
 	fn apply_extrinsic_no_note_with_len(uxt: Block::Extrinsic, encoded_len: usize) -> result::Result<internal::ApplyOutcome, internal::ApplyError> {
 		// Verify the signature is good.
-		let xt = uxt.check(Lookup::lookup).map_err(internal::ApplyError::BadSignature)?;
+		let xt = uxt.check_with(Lookup::lookup).map_err(|_| internal::ApplyError::BadSignature(""))?;
 
 		if xt.sender() != &Default::default() {
 			// check index

From 6a90ab5d79bccc3178995b8d30dc8f2efb51429b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:14:31 +0200
Subject: [PATCH 09/21] tx-pool: replace CheckedIntrinsic type alias since it
 now would require type param

---
 polkadot/runtime/src/lib.rs          | 2 ++
 polkadot/transaction-pool/src/lib.rs | 5 +----
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/polkadot/runtime/src/lib.rs b/polkadot/runtime/src/lib.rs
index 746607a932f39..37611e388cb7d 100644
--- a/polkadot/runtime/src/lib.rs
+++ b/polkadot/runtime/src/lib.rs
@@ -92,6 +92,8 @@ pub type Address = staking::Address<Concrete>;
 pub type BlockId = generic::BlockId<Block>;
 /// Unchecked extrinsic type as expected by this runtime.
 pub type UncheckedExtrinsic = generic::UncheckedExtrinsic<Address, Index, Call, Signature>;
+/// Checked extrinsic type as expected by this runtime.
+pub type CheckedExtrinsic = generic::CheckedExtrinsic<Address, Index, Call>;
 /// Extrinsic type as expected by this runtime. This is not the type that is signed.
 pub type Extrinsic = generic::Extrinsic<Address, Index, Call>;
 /// Extrinsic type that is signed.
diff --git a/polkadot/transaction-pool/src/lib.rs b/polkadot/transaction-pool/src/lib.rs
index e8ff48aa44fe4..a08332ceb5dc6 100644
--- a/polkadot/transaction-pool/src/lib.rs
+++ b/polkadot/transaction-pool/src/lib.rs
@@ -48,15 +48,12 @@ use extrinsic_pool::{Pool, Listener, txpool::{self, Readiness, scoring::{Change,
 use extrinsic_pool::api::ExtrinsicPool;
 use polkadot_api::PolkadotApi;
 use primitives::{AccountId, BlockId, Hash, Index, UncheckedExtrinsic as FutureProofUncheckedExtrinsic};
-use runtime::{Address, UncheckedExtrinsic};
+use runtime::{Address, UncheckedExtrinsic, CheckedExtrinsic};
 use substrate_runtime_primitives::traits::{Bounded, Checkable, Hashing, BlakeTwo256};
 
 pub use extrinsic_pool::txpool::{Options, Status, LightStatus, VerifiedTransaction as VerifiedTransactionOps};
 pub use error::{Error, ErrorKind, Result};
 
-/// Type alias for convenience.
-pub type CheckedExtrinsic = <UncheckedExtrinsic as Checkable>::Checked;
-
 /// A verified transaction which should be includable and non-inherent.
 #[derive(Clone, Debug)]
 pub struct VerifiedTransaction {

From de69b7a4c47b4a3b9ff9dc7560319695d9269013 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:15:42 +0200
Subject: [PATCH 10/21] make more uses of Checkable compile

---
 substrate/runtime/primitives/src/generic.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/substrate/runtime/primitives/src/generic.rs b/substrate/runtime/primitives/src/generic.rs
index 20b733f9c9897..62722beb8c32b 100644
--- a/substrate/runtime/primitives/src/generic.rs
+++ b/substrate/runtime/primitives/src/generic.rs
@@ -106,7 +106,7 @@ where
 	AccountId: Member + Default + MaybeDisplay,
 	::MaybeUnsigned<Signature>: Member,
 	Extrinsic<AccountId, Index, Call>: Slicable,
-	ThisLookup: FnOnce(&Address) -> Result<AccountId, &'static str>,
+	ThisLookup: FnOnce(Address) -> Result<AccountId, &'static str>,
 {
 	type Checked = CheckedExtrinsic<AccountId, Index, Call>;
 
@@ -120,7 +120,7 @@ where
 		} else {
 			let extrinsic: Extrinsic<AccountId, Index, Call>
 				= Extrinsic {
-					signed: match lookup(&self.extrinsic.signed) {
+					signed: match lookup(self.extrinsic.signed.clone()) {
 						Ok(x) => x,
 						Err(_) => return Err(self)
 					},

From 574b2a8338749c9008179cb45b8282677af86cc1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:17:16 +0200
Subject: [PATCH 11/21] adapt Executive impl to new Checkable trait

---
 substrate/runtime/executive/src/lib.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index 9ccf3c77c80d3..6349b7f38b2ac 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -84,12 +84,12 @@ pub struct Executive<
 impl<
 	System: system::Trait,
 	Block: traits::Block<Header=System::Header, Hash=System::Hash>,
-	Lookup: AuxLookup<Source=<Block::Extrinsic as Checkable>::Address, Target=System::AccountId>,
+	Lookup: AuxLookup<Source=System::Address, Target=System::AccountId>,
 	Payment: MakePayment<System::AccountId>,
 	Finalisation: Executable,
 > Executive<System, Block, Lookup, Payment, Finalisation> where
-	Block::Extrinsic: Checkable<AccountId=System::AccountId> + Slicable,
-	<Block::Extrinsic as Checkable>::Checked: Applyable<Index=System::Index, AccountId=System::AccountId>
+	Block::Extrinsic: Checkable<fn(System::Address) -> Result<System::AccountId, &'static str>> + Slicable,
+	<Block::Extrinsic as Checkable<fn(System::Address) -> Result<System::AccountId, &'static str>>>::Checked: Applyable<Index=System::Index, AccountId=System::AccountId>
 {
 	/// Start the execution of a particular block.
 	pub fn initialise_block(header: &System::Header) {

From 8da0a5a5f07cd6aab59cf52752d59a250099deac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 21:45:51 +0200
Subject: [PATCH 12/21] fix that CheckedExtrinsic takes AccountId not Address
 as first type param

---
 polkadot/runtime/src/lib.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/polkadot/runtime/src/lib.rs b/polkadot/runtime/src/lib.rs
index 37611e388cb7d..450db7288ab7e 100644
--- a/polkadot/runtime/src/lib.rs
+++ b/polkadot/runtime/src/lib.rs
@@ -93,7 +93,7 @@ pub type BlockId = generic::BlockId<Block>;
 /// Unchecked extrinsic type as expected by this runtime.
 pub type UncheckedExtrinsic = generic::UncheckedExtrinsic<Address, Index, Call, Signature>;
 /// Checked extrinsic type as expected by this runtime.
-pub type CheckedExtrinsic = generic::CheckedExtrinsic<Address, Index, Call>;
+pub type CheckedExtrinsic = generic::CheckedExtrinsic<AccountId, Index, Call>;
 /// Extrinsic type as expected by this runtime. This is not the type that is signed.
 pub type Extrinsic = generic::Extrinsic<Address, Index, Call>;
 /// Extrinsic type that is signed.

From 7cccc1d70447df8732acb610471788f5a8688e07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 22:46:10 +0200
Subject: [PATCH 13/21] Checkable trait: return error again since it's required
 in some cases

---
 polkadot/transaction-pool/src/lib.rs        |  4 ++--
 substrate/runtime/primitives/src/generic.rs |  9 +++++----
 substrate/runtime/primitives/src/testing.rs |  3 ++-
 substrate/runtime/primitives/src/traits.rs  | 13 ++++++++++---
 substrate/test-runtime/src/lib.rs           |  5 +++--
 5 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/polkadot/transaction-pool/src/lib.rs b/polkadot/transaction-pool/src/lib.rs
index a08332ceb5dc6..c9a7ab169c4e5 100644
--- a/polkadot/transaction-pool/src/lib.rs
+++ b/polkadot/transaction-pool/src/lib.rs
@@ -281,8 +281,8 @@ impl<'a, A> txpool::Verifier<UncheckedExtrinsic> for Verifier<'a, A> where
 		let inner = match uxt.clone().check_with(|a| self.lookup(a)) {
 			Ok(xt) => Some(xt),
 			// keep the transaction around in the future pool and attempt to promote it later.
-			Err(Self::NO_ACCOUNT) => None,
-			Err(e) => bail!(e),
+			Err((_, Self::NO_ACCOUNT)) => None,
+			Err((_, e)) => bail!(e),
 		};
 		let sender = inner.as_ref().map(|x| x.signed.clone());
 
diff --git a/substrate/runtime/primitives/src/generic.rs b/substrate/runtime/primitives/src/generic.rs
index 62722beb8c32b..2487e7afeb4b2 100644
--- a/substrate/runtime/primitives/src/generic.rs
+++ b/substrate/runtime/primitives/src/generic.rs
@@ -109,8 +109,9 @@ where
 	ThisLookup: FnOnce(Address) -> Result<AccountId, &'static str>,
 {
 	type Checked = CheckedExtrinsic<AccountId, Index, Call>;
+	type Error = &'static str;
 
-	fn check_with(self, lookup: ThisLookup) -> Result<Self::Checked, Self> {
+	fn check_with(self, lookup: ThisLookup) -> Result<Self::Checked, (Self, Self::Error)> {
 		if !self.is_signed() {
 			Ok(CheckedExtrinsic(Extrinsic {
 				signed: Default::default(),
@@ -121,8 +122,8 @@ where
 			let extrinsic: Extrinsic<AccountId, Index, Call>
 				= Extrinsic {
 					signed: match lookup(self.extrinsic.signed.clone()) {
-						Ok(x) => x,
-						Err(_) => return Err(self)
+						Ok(success) => success,
+						Err(error) => return Err((self, error)),
 					},
 					index: self.extrinsic.index.clone(),
 					function: self.extrinsic.function.clone(),
@@ -130,7 +131,7 @@ where
 			if ::verify_encoded_lazy(&self.signature, &extrinsic, &extrinsic.signed) {
 				Ok(CheckedExtrinsic(extrinsic))
 			} else {
-				Err(self)
+				Err((self, "bad signature in extrinsic"))
 			}
 		}
 	}
diff --git a/substrate/runtime/primitives/src/testing.rs b/substrate/runtime/primitives/src/testing.rs
index 2b36ec8d057cf..77788b2925979 100644
--- a/substrate/runtime/primitives/src/testing.rs
+++ b/substrate/runtime/primitives/src/testing.rs
@@ -158,8 +158,9 @@ impl<Call: AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + Deseri
 	}
 }
 impl<Call: 'static + AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug, Ctx> Checkable<Ctx> for TestXt<Call> {
+	type Error = ();
 	type Checked = Self;
-	fn check_with(self, _: Ctx) -> Result<Self::Checked, Self> { Ok(self) }
+	fn check_with(self, _: Ctx) -> Result<Self::Checked, (Self, ())> { Ok(self) }
 }
 impl<Call: AuxDispatchable<Aux = u64> + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug> Applyable for TestXt<Call> {
 	type AccountId = u64;
diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 56a45a1556d08..2cc84f03c6db6 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -373,25 +373,32 @@ pub type HashingFor<B> = <<B as Block>::Header as Header>::Hashing;
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
 /// for things that can be checked by providing additional context `Ctx`
 pub trait Checkable<Ctx>: Sized {
+	/// returned in case the check succeeds
 	type Checked;
+	/// returned in case the check fails
+	type Error;
 
-	fn check_with(self, ctx: Ctx) -> Result<Self::Checked, Self>;
+	fn check_with(self, ctx: Ctx) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
 /// for things that can be checked without additional context.
 pub trait BlindCheckable: Sized {
+	/// returned in case the check succeeds
 	type Checked;
+	/// returned in case the check fails
+	type Error;
 
 	/// gives back in case of an error.
-	fn check(self) -> Result<Self::Checked, Self>;
+	fn check(self) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
 // every BlindCheckable is also a Checkable for arbitrary context `Ctx`
 impl<T: BlindCheckable, Ctx> Checkable<Ctx> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
-	fn check_with(self, _: Ctx) -> Result<Self::Checked, Self> {
+	type Error = T::Error;
+	fn check_with(self, _: Ctx) -> Result<Self::Checked, (Self, Self::Error)> {
 		BlindCheckable::check(self)
 	}
 }
diff --git a/substrate/test-runtime/src/lib.rs b/substrate/test-runtime/src/lib.rs
index 6f9da3a93d8ed..ddf2d40d2c7bf 100644
--- a/substrate/test-runtime/src/lib.rs
+++ b/substrate/test-runtime/src/lib.rs
@@ -119,12 +119,13 @@ impl Slicable for Extrinsic {
 
 impl BlindCheckable for Extrinsic {
 	type Checked = Self;
+	type Error = &'static str;
 
-	fn check(self) -> Result<Self, Self> {
+	fn check(self) -> Result<Self, (Self, Self::Error)> {
 		if ::runtime_primitives::verify_encoded_lazy(&self.signature, &self.transfer, &self.transfer.from) {
 			Ok(self)
 		} else {
-			Err(self)
+			Err((self, "bad signature"))
 		}
 	}
 }

From b147c0a43fc3044d44203691da99e76be8533fd4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Fri, 6 Jul 2018 22:59:02 +0200
Subject: [PATCH 14/21] Checkable: improve docstrings

---
 substrate/runtime/primitives/src/traits.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 2cc84f03c6db6..45323ba5159c5 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -378,6 +378,7 @@ pub trait Checkable<Ctx>: Sized {
 	/// returned in case the check fails
 	type Error;
 
+	/// gives back unchanged `self` in case of an error.
 	fn check_with(self, ctx: Ctx) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
@@ -390,7 +391,7 @@ pub trait BlindCheckable: Sized {
 	/// returned in case the check fails
 	type Error;
 
-	/// gives back in case of an error.
+	/// gives back unchanged `self` in case of an error.
 	fn check(self) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 

From 7642b81b2468fe4d04be1f3868364c6b7005b32a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Sun, 8 Jul 2018 00:53:50 +0200
Subject: [PATCH 15/21] consistent punctuation and capitalization in docstrings

---
 substrate/runtime/primitives/src/traits.rs | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 45323ba5159c5..e7ffcb1d8066d 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -371,31 +371,33 @@ pub type HashingFor<B> = <<B as Block>::Header as Header>::Hashing;
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
-/// for things that can be checked by providing additional context `Ctx`
+/// Implement for pieces of information that require some additional context `Ctx` in order to be
+/// checked.
 pub trait Checkable<Ctx>: Sized {
-	/// returned in case the check succeeds
+	/// Returned if `check_with` succeeds.
 	type Checked;
-	/// returned in case the check fails
+	/// Returned if `check_with` fails.
 	type Error;
 
-	/// gives back unchanged `self` in case of an error.
+	/// Gives back ownership of unchanged `self` in case of an error.
 	fn check_with(self, ctx: Ctx) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
-/// for things that can be checked without additional context.
+/// Implement for pieces of information that don't require additional context in order to be
+/// checked.
 pub trait BlindCheckable: Sized {
-	/// returned in case the check succeeds
+	/// Returned if `check` succeeds.
 	type Checked;
-	/// returned in case the check fails
+	/// Returned if `check` fails.
 	type Error;
 
-	/// gives back unchanged `self` in case of an error.
+	/// Gives back ownership of unchanged `self` in case of an error.
 	fn check(self) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
-// every BlindCheckable is also a Checkable for arbitrary context `Ctx`
+// Every `BlindCheckable` is also a `Checkable` for arbitrary context `Ctx`.
 impl<T: BlindCheckable, Ctx> Checkable<Ctx> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
 	type Error = T::Error;

From 70ab21073b63e65347cfdd4e732f9d97d231bd13 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Mon, 9 Jul 2018 20:13:00 +0200
Subject: [PATCH 16/21] Ctx -> Context

addresses https://github.com/paritytech/polkadot/pull/287#discussion_r200956240
---
 substrate/runtime/primitives/src/testing.rs |  4 ++--
 substrate/runtime/primitives/src/traits.rs  | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/substrate/runtime/primitives/src/testing.rs b/substrate/runtime/primitives/src/testing.rs
index 77788b2925979..5438e80c5bc1f 100644
--- a/substrate/runtime/primitives/src/testing.rs
+++ b/substrate/runtime/primitives/src/testing.rs
@@ -157,10 +157,10 @@ impl<Call: AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + Deseri
 		self.0.encode()
 	}
 }
-impl<Call: 'static + AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug, Ctx> Checkable<Ctx> for TestXt<Call> {
+impl<Call: 'static + AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug, Context> Checkable<Context> for TestXt<Call> {
 	type Error = ();
 	type Checked = Self;
-	fn check_with(self, _: Ctx) -> Result<Self::Checked, (Self, ())> { Ok(self) }
+	fn check_with(self, _: Context) -> Result<Self::Checked, (Self, ())> { Ok(self) }
 }
 impl<Call: AuxDispatchable<Aux = u64> + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug> Applyable for TestXt<Call> {
 	type AccountId = u64;
diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index e7ffcb1d8066d..28a09bc9fdde0 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -371,16 +371,16 @@ pub type HashingFor<B> = <<B as Block>::Header as Header>::Hashing;
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
 /// check the validity of a piece of extrinsic information, usually by verifying the signature.
-/// Implement for pieces of information that require some additional context `Ctx` in order to be
+/// Implement for pieces of information that require some additional context `Context` in order to be
 /// checked.
-pub trait Checkable<Ctx>: Sized {
+pub trait Checkable<Context>: Sized {
 	/// Returned if `check_with` succeeds.
 	type Checked;
 	/// Returned if `check_with` fails.
 	type Error;
 
 	/// Gives back ownership of unchanged `self` in case of an error.
-	fn check_with(self, ctx: Ctx) -> Result<Self::Checked, (Self, Self::Error)>;
+	fn check_with(self, context: Context) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
@@ -397,11 +397,11 @@ pub trait BlindCheckable: Sized {
 	fn check(self) -> Result<Self::Checked, (Self, Self::Error)>;
 }
 
-// Every `BlindCheckable` is also a `Checkable` for arbitrary context `Ctx`.
-impl<T: BlindCheckable, Ctx> Checkable<Ctx> for T {
+// Every `BlindCheckable` is also a `Checkable` for arbitrary `Context`.
+impl<T: BlindCheckable, Context> Checkable<Context> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
 	type Error = T::Error;
-	fn check_with(self, _: Ctx) -> Result<Self::Checked, (Self, Self::Error)> {
+	fn check_with(self, _: Context) -> Result<Self::Checked, (Self, Self::Error)> {
 		BlindCheckable::check(self)
 	}
 }

From f4fcebb8d3700a2642560cb7b4e486eecb8d5977 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Mon, 9 Jul 2018 20:33:03 +0200
Subject: [PATCH 17/21] reduce trait bounds for impl Checkable for TestXt

addresses https://github.com/paritytech/polkadot/pull/287#discussion_r200839303
---
 substrate/runtime/primitives/src/testing.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/substrate/runtime/primitives/src/testing.rs b/substrate/runtime/primitives/src/testing.rs
index 5438e80c5bc1f..a8436bd2d4ff3 100644
--- a/substrate/runtime/primitives/src/testing.rs
+++ b/substrate/runtime/primitives/src/testing.rs
@@ -157,7 +157,7 @@ impl<Call: AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + Deseri
 		self.0.encode()
 	}
 }
-impl<Call: 'static + AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug, Context> Checkable<Context> for TestXt<Call> {
+impl<Call: Slicable + Sync + Send + Serialize + AuxDispatchable, Context> Checkable<Context> for TestXt<Call> {
 	type Error = ();
 	type Checked = Self;
 	fn check_with(self, _: Context) -> Result<Self::Checked, (Self, ())> { Ok(self) }

From 21676fe8a80c52fb68c8b1d0e2f5dd5811f2c529 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Mon, 9 Jul 2018 22:46:50 +0200
Subject: [PATCH 18/21] use <UncheckedExtrinsic as Checkable>::Checked

addresses https://github.com/paritytech/polkadot/pull/287#discussion_r200955165
---
 polkadot/runtime/src/lib.rs          | 2 --
 polkadot/transaction-pool/src/lib.rs | 5 ++++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/polkadot/runtime/src/lib.rs b/polkadot/runtime/src/lib.rs
index 450db7288ab7e..746607a932f39 100644
--- a/polkadot/runtime/src/lib.rs
+++ b/polkadot/runtime/src/lib.rs
@@ -92,8 +92,6 @@ pub type Address = staking::Address<Concrete>;
 pub type BlockId = generic::BlockId<Block>;
 /// Unchecked extrinsic type as expected by this runtime.
 pub type UncheckedExtrinsic = generic::UncheckedExtrinsic<Address, Index, Call, Signature>;
-/// Checked extrinsic type as expected by this runtime.
-pub type CheckedExtrinsic = generic::CheckedExtrinsic<AccountId, Index, Call>;
 /// Extrinsic type as expected by this runtime. This is not the type that is signed.
 pub type Extrinsic = generic::Extrinsic<Address, Index, Call>;
 /// Extrinsic type that is signed.
diff --git a/polkadot/transaction-pool/src/lib.rs b/polkadot/transaction-pool/src/lib.rs
index c9a7ab169c4e5..38d3096f02768 100644
--- a/polkadot/transaction-pool/src/lib.rs
+++ b/polkadot/transaction-pool/src/lib.rs
@@ -48,12 +48,15 @@ use extrinsic_pool::{Pool, Listener, txpool::{self, Readiness, scoring::{Change,
 use extrinsic_pool::api::ExtrinsicPool;
 use polkadot_api::PolkadotApi;
 use primitives::{AccountId, BlockId, Hash, Index, UncheckedExtrinsic as FutureProofUncheckedExtrinsic};
-use runtime::{Address, UncheckedExtrinsic, CheckedExtrinsic};
+use runtime::{Address, UncheckedExtrinsic};
 use substrate_runtime_primitives::traits::{Bounded, Checkable, Hashing, BlakeTwo256};
 
 pub use extrinsic_pool::txpool::{Options, Status, LightStatus, VerifiedTransaction as VerifiedTransactionOps};
 pub use error::{Error, ErrorKind, Result};
 
+/// Type alias for convenience.
+pub type CheckedExtrinsic = <UncheckedExtrinsic as Checkable<fn(Address) -> std::result::Result<AccountId, &'static str>>>::Checked;
+
 /// A verified transaction which should be includable and non-inherent.
 #[derive(Clone, Debug)]
 pub struct VerifiedTransaction {

From 2e3e4a89e46135f2c7dd2f39411c92025bb42e9e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Mon, 9 Jul 2018 23:04:26 +0200
Subject: [PATCH 19/21] Revert "add ::Address to system::Trait since its no
 longer in Checkable trait"

This reverts commit 02eb103015b833c995c9f9067aac2542bb7ce5ea.
---
 demo/runtime/src/lib.rs                | 1 -
 polkadot/runtime/src/lib.rs            | 1 -
 polkadot/runtime/src/parachains.rs     | 1 -
 substrate/runtime/council/src/lib.rs   | 1 -
 substrate/runtime/democracy/src/lib.rs | 1 -
 substrate/runtime/executive/src/lib.rs | 1 -
 substrate/runtime/session/src/lib.rs   | 1 -
 substrate/runtime/staking/src/mock.rs  | 1 -
 substrate/runtime/system/src/lib.rs    | 1 -
 substrate/runtime/timestamp/src/lib.rs | 1 -
 10 files changed, 10 deletions(-)

diff --git a/demo/runtime/src/lib.rs b/demo/runtime/src/lib.rs
index f65d21e5868a7..938bcbbfa2be3 100644
--- a/demo/runtime/src/lib.rs
+++ b/demo/runtime/src/lib.rs
@@ -89,7 +89,6 @@ impl system::Trait for Concrete {
 	type Hashing = BlakeTwo256;
 	type Digest = generic::Digest<Vec<u8>>;
 	type AccountId = AccountId;
-	type Address = Address;
 	type Header = generic::Header<BlockNumber, BlakeTwo256, Vec<u8>>;
 }
 
diff --git a/polkadot/runtime/src/lib.rs b/polkadot/runtime/src/lib.rs
index 746607a932f39..532de07cd76ef 100644
--- a/polkadot/runtime/src/lib.rs
+++ b/polkadot/runtime/src/lib.rs
@@ -132,7 +132,6 @@ impl system::Trait for Concrete {
 	type Hashing = BlakeTwo256;
 	type Digest = generic::Digest<Log>;
 	type AccountId = AccountId;
-	type Address = Address;
 	type Header = Header;
 }
 /// System module for this concrete runtime.
diff --git a/polkadot/runtime/src/parachains.rs b/polkadot/runtime/src/parachains.rs
index 9486be6c92cc8..3625633adf392 100644
--- a/polkadot/runtime/src/parachains.rs
+++ b/polkadot/runtime/src/parachains.rs
@@ -254,7 +254,6 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
-		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/council/src/lib.rs b/substrate/runtime/council/src/lib.rs
index 6e955c712792a..e6c3c9b4164d4 100644
--- a/substrate/runtime/council/src/lib.rs
+++ b/substrate/runtime/council/src/lib.rs
@@ -647,7 +647,6 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
-		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/democracy/src/lib.rs b/substrate/runtime/democracy/src/lib.rs
index 393a478b46ee9..c20d60d2de359 100644
--- a/substrate/runtime/democracy/src/lib.rs
+++ b/substrate/runtime/democracy/src/lib.rs
@@ -389,7 +389,6 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
-		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index 6349b7f38b2ac..bd918df94f806 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -248,7 +248,6 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
-		type Address = u64;
 		type Header = Header;
 	}
 	impl session::Trait for Test {
diff --git a/substrate/runtime/session/src/lib.rs b/substrate/runtime/session/src/lib.rs
index 7a301bd14bc39..74debe5a84e24 100644
--- a/substrate/runtime/session/src/lib.rs
+++ b/substrate/runtime/session/src/lib.rs
@@ -283,7 +283,6 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
-		type Address = u64;
 		type Header = Header;
 	}
 	impl timestamp::Trait for Test {
diff --git a/substrate/runtime/staking/src/mock.rs b/substrate/runtime/staking/src/mock.rs
index 254276a2a3322..c2cf48dbd19ab 100644
--- a/substrate/runtime/staking/src/mock.rs
+++ b/substrate/runtime/staking/src/mock.rs
@@ -43,7 +43,6 @@ impl system::Trait for Test {
 	type Hashing = ::primitives::traits::BlakeTwo256;
 	type Digest = Digest;
 	type AccountId = u64;
-	type Address = u64;
 	type Header = Header;
 }
 impl session::Trait for Test {
diff --git a/substrate/runtime/system/src/lib.rs b/substrate/runtime/system/src/lib.rs
index dce921f6d8f5f..e5e0b47a29b9f 100644
--- a/substrate/runtime/system/src/lib.rs
+++ b/substrate/runtime/system/src/lib.rs
@@ -69,7 +69,6 @@ pub trait Trait: Eq + Clone {
 	type Hashing: Hashing<Output = Self::Hash>;
 	type Digest: Parameter + Member + Default + traits::Digest;
 	type AccountId: Parameter + Member + MaybeDisplay + Ord + Default;
-	type Address: Parameter + Member + MaybeDisplay;
 	type Header: Parameter + traits::Header<
 		Number = Self::BlockNumber,
 		Hashing = Self::Hashing,
diff --git a/substrate/runtime/timestamp/src/lib.rs b/substrate/runtime/timestamp/src/lib.rs
index 497bf6f06819f..f541e0a11f30a 100644
--- a/substrate/runtime/timestamp/src/lib.rs
+++ b/substrate/runtime/timestamp/src/lib.rs
@@ -158,7 +158,6 @@ mod tests {
 		type Hashing = BlakeTwo256;
 		type Digest = Digest;
 		type AccountId = u64;
-		type Address = u64;
 		type Header = Header;
 	}
 	impl consensus::Trait for Test {

From 6e550d889fbbd2104368443d3251bdc639c95a46 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Mon, 9 Jul 2018 23:10:22 +0200
Subject: [PATCH 20/21] runtime/executive: properly fix that Address no longer
 in Checkable

---
 substrate/runtime/executive/src/lib.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index bd918df94f806..67baf12ea4aee 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -82,14 +82,15 @@ pub struct Executive<
 >(PhantomData<(System, Block, Lookup, Payment, Finalisation)>);
 
 impl<
+	Address,
 	System: system::Trait,
 	Block: traits::Block<Header=System::Header, Hash=System::Hash>,
-	Lookup: AuxLookup<Source=System::Address, Target=System::AccountId>,
+	Lookup: AuxLookup<Source=Address, Target=System::AccountId>,
 	Payment: MakePayment<System::AccountId>,
 	Finalisation: Executable,
 > Executive<System, Block, Lookup, Payment, Finalisation> where
-	Block::Extrinsic: Checkable<fn(System::Address) -> Result<System::AccountId, &'static str>> + Slicable,
-	<Block::Extrinsic as Checkable<fn(System::Address) -> Result<System::AccountId, &'static str>>>::Checked: Applyable<Index=System::Index, AccountId=System::AccountId>
+	Block::Extrinsic: Checkable<fn(Address) -> Result<System::AccountId, &'static str>> + Slicable,
+	<Block::Extrinsic as Checkable<fn(Address) -> Result<System::AccountId, &'static str>>>::Checked: Applyable<Index=System::Index, AccountId=System::AccountId>
 {
 	/// Start the execution of a particular block.
 	pub fn initialise_block(header: &System::Header) {

From eef85e1c5a024f99a94cea9a4f84bd9391e1339b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Kru=CC=88ger?= <kruemaxi@googlemail.com>
Date: Tue, 10 Jul 2018 20:24:36 +0200
Subject: [PATCH 21/21] return `Result<Self::Checked, &'static str>` from
 `Checkable::check`

---
 polkadot/transaction-pool/src/lib.rs        |  4 ++--
 substrate/runtime/executive/src/lib.rs      |  2 +-
 substrate/runtime/primitives/src/generic.rs | 14 +++++---------
 substrate/runtime/primitives/src/testing.rs |  3 +--
 substrate/runtime/primitives/src/traits.rs  | 13 +++----------
 substrate/test-runtime/src/lib.rs           |  5 ++---
 6 files changed, 14 insertions(+), 27 deletions(-)

diff --git a/polkadot/transaction-pool/src/lib.rs b/polkadot/transaction-pool/src/lib.rs
index 38d3096f02768..85b06698b0179 100644
--- a/polkadot/transaction-pool/src/lib.rs
+++ b/polkadot/transaction-pool/src/lib.rs
@@ -284,8 +284,8 @@ impl<'a, A> txpool::Verifier<UncheckedExtrinsic> for Verifier<'a, A> where
 		let inner = match uxt.clone().check_with(|a| self.lookup(a)) {
 			Ok(xt) => Some(xt),
 			// keep the transaction around in the future pool and attempt to promote it later.
-			Err((_, Self::NO_ACCOUNT)) => None,
-			Err((_, e)) => bail!(e),
+			Err(Self::NO_ACCOUNT) => None,
+			Err(e) => bail!(e),
 		};
 		let sender = inner.as_ref().map(|x| x.signed.clone());
 
diff --git a/substrate/runtime/executive/src/lib.rs b/substrate/runtime/executive/src/lib.rs
index 67baf12ea4aee..fd4e9a0c0e3a7 100644
--- a/substrate/runtime/executive/src/lib.rs
+++ b/substrate/runtime/executive/src/lib.rs
@@ -173,7 +173,7 @@ impl<
 	/// Actually apply an extrinsic given its `encoded_len`; this doesn't note its hash.
 	fn apply_extrinsic_no_note_with_len(uxt: Block::Extrinsic, encoded_len: usize) -> result::Result<internal::ApplyOutcome, internal::ApplyError> {
 		// Verify the signature is good.
-		let xt = uxt.check_with(Lookup::lookup).map_err(|_| internal::ApplyError::BadSignature(""))?;
+		let xt = uxt.check_with(Lookup::lookup).map_err(internal::ApplyError::BadSignature)?;
 
 		if xt.sender() != &Default::default() {
 			// check index
diff --git a/substrate/runtime/primitives/src/generic.rs b/substrate/runtime/primitives/src/generic.rs
index 2487e7afeb4b2..0c50b2d8f7b01 100644
--- a/substrate/runtime/primitives/src/generic.rs
+++ b/substrate/runtime/primitives/src/generic.rs
@@ -109,9 +109,8 @@ where
 	ThisLookup: FnOnce(Address) -> Result<AccountId, &'static str>,
 {
 	type Checked = CheckedExtrinsic<AccountId, Index, Call>;
-	type Error = &'static str;
 
-	fn check_with(self, lookup: ThisLookup) -> Result<Self::Checked, (Self, Self::Error)> {
+	fn check_with(self, lookup: ThisLookup) -> Result<Self::Checked, &'static str> {
 		if !self.is_signed() {
 			Ok(CheckedExtrinsic(Extrinsic {
 				signed: Default::default(),
@@ -121,17 +120,14 @@ where
 		} else {
 			let extrinsic: Extrinsic<AccountId, Index, Call>
 				= Extrinsic {
-					signed: match lookup(self.extrinsic.signed.clone()) {
-						Ok(success) => success,
-						Err(error) => return Err((self, error)),
-					},
-					index: self.extrinsic.index.clone(),
-					function: self.extrinsic.function.clone(),
+					signed: lookup(self.extrinsic.signed)?,
+					index: self.extrinsic.index,
+					function: self.extrinsic.function,
 				};
 			if ::verify_encoded_lazy(&self.signature, &extrinsic, &extrinsic.signed) {
 				Ok(CheckedExtrinsic(extrinsic))
 			} else {
-				Err((self, "bad signature in extrinsic"))
+				Err("bad signature in extrinsic")
 			}
 		}
 	}
diff --git a/substrate/runtime/primitives/src/testing.rs b/substrate/runtime/primitives/src/testing.rs
index a8436bd2d4ff3..12e347e1e3a8b 100644
--- a/substrate/runtime/primitives/src/testing.rs
+++ b/substrate/runtime/primitives/src/testing.rs
@@ -158,9 +158,8 @@ impl<Call: AuxDispatchable + Slicable + Sized + Send + Sync + Serialize + Deseri
 	}
 }
 impl<Call: Slicable + Sync + Send + Serialize + AuxDispatchable, Context> Checkable<Context> for TestXt<Call> {
-	type Error = ();
 	type Checked = Self;
-	fn check_with(self, _: Context) -> Result<Self::Checked, (Self, ())> { Ok(self) }
+	fn check_with(self, _: Context) -> Result<Self::Checked, &'static str> { Ok(self) }
 }
 impl<Call: AuxDispatchable<Aux = u64> + Slicable + Sized + Send + Sync + Serialize + DeserializeOwned + Clone + Eq + Debug> Applyable for TestXt<Call> {
 	type AccountId = u64;
diff --git a/substrate/runtime/primitives/src/traits.rs b/substrate/runtime/primitives/src/traits.rs
index 28a09bc9fdde0..aafbcc56be57a 100644
--- a/substrate/runtime/primitives/src/traits.rs
+++ b/substrate/runtime/primitives/src/traits.rs
@@ -376,11 +376,8 @@ pub type HashingFor<B> = <<B as Block>::Header as Header>::Hashing;
 pub trait Checkable<Context>: Sized {
 	/// Returned if `check_with` succeeds.
 	type Checked;
-	/// Returned if `check_with` fails.
-	type Error;
 
-	/// Gives back ownership of unchanged `self` in case of an error.
-	fn check_with(self, context: Context) -> Result<Self::Checked, (Self, Self::Error)>;
+	fn check_with(self, context: Context) -> Result<Self::Checked, &'static str>;
 }
 
 /// A "checkable" piece of information, used by the standard Substrate Executive in order to
@@ -390,18 +387,14 @@ pub trait Checkable<Context>: Sized {
 pub trait BlindCheckable: Sized {
 	/// Returned if `check` succeeds.
 	type Checked;
-	/// Returned if `check` fails.
-	type Error;
 
-	/// Gives back ownership of unchanged `self` in case of an error.
-	fn check(self) -> Result<Self::Checked, (Self, Self::Error)>;
+	fn check(self) -> Result<Self::Checked, &'static str>;
 }
 
 // Every `BlindCheckable` is also a `Checkable` for arbitrary `Context`.
 impl<T: BlindCheckable, Context> Checkable<Context> for T {
 	type Checked = <Self as BlindCheckable>::Checked;
-	type Error = T::Error;
-	fn check_with(self, _: Context) -> Result<Self::Checked, (Self, Self::Error)> {
+	fn check_with(self, _: Context) -> Result<Self::Checked, &'static str> {
 		BlindCheckable::check(self)
 	}
 }
diff --git a/substrate/test-runtime/src/lib.rs b/substrate/test-runtime/src/lib.rs
index ddf2d40d2c7bf..ee4357aaeee76 100644
--- a/substrate/test-runtime/src/lib.rs
+++ b/substrate/test-runtime/src/lib.rs
@@ -119,13 +119,12 @@ impl Slicable for Extrinsic {
 
 impl BlindCheckable for Extrinsic {
 	type Checked = Self;
-	type Error = &'static str;
 
-	fn check(self) -> Result<Self, (Self, Self::Error)> {
+	fn check(self) -> Result<Self, &'static str> {
 		if ::runtime_primitives::verify_encoded_lazy(&self.signature, &self.transfer, &self.transfer.from) {
 			Ok(self)
 		} else {
-			Err((self, "bad signature"))
+			Err("bad signature")
 		}
 	}
 }