Document more TODOs as tickets (#1418)

Went through the TODOs, removed a bunch, which are outdated or nothing more than a regular comment, documented a bunch more as actual tickets and made them FIXMEs and unified their structure (`FIXME #TICKETNO DESC` for local tickets, `FIXME: DESC LINK` for external tickets) for easier in-editor support. Further more remove unnecessary remarks and related old code that I noticed in that instance.

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

@@ -16,8 +16,8 @@
 
 //! A consensus proposer for "basic" chains which use the primitive inherent-data.
 
-// FIXME: move this into substrate-consensus-common - https://github.com/paritytech/substrate/issues/1021
-
+// FIXME #1021 move this into substrate-consensus-common
+// 
 use std::{sync::Arc, self};
 
 use log::{info, trace};
@@ -197,7 +197,6 @@ impl<Block, C, A> Proposer<Block, C, A>	where
 				let pending_iterator = self.transaction_pool.ready();
 
 				for pending in pending_iterator {
-					// TODO [ToDr] Probably get rid of it, and validate in runtime.
 					let encoded_size = pending.data.encode().len();
 					if pending_size + encoded_size >= MAX_TRANSACTIONS_SIZE { break }
 

substrate/core/client/db/src/lib.rs

@@ -307,7 +307,6 @@ where Block: BlockT<Hash=H256>,
 	}
 
 	fn reset_storage(&mut self, mut top: StorageMap, children: ChildrenStorageMap) -> Result<H256, client::error::Error> {
-		// TODO: wipe out existing trie.
 
 		if top.iter().any(|(k, _)| well_known_keys::is_child_storage_key(k)) {
 			return Err(client::error::ErrorKind::GenesisInvalid.into());
@@ -384,7 +383,7 @@ struct DbGenesisStorage(pub H256);
 impl DbGenesisStorage {
 	pub fn new() -> Self {
 		let mut root = H256::default();
-		let mut mdb = MemoryDB::<Blake2Hasher>::default();	// TODO: use new() to make it more correct
+		let mut mdb = MemoryDB::<Blake2Hasher>::default();
 		state_machine::TrieDBMut::<Blake2Hasher>::new(&mut mdb, &mut root);
 		DbGenesisStorage(root)
 	}
@@ -1024,7 +1023,7 @@ mod tests {
 
 	fn prepare_changes(changes: Vec<(Vec<u8>, Vec<u8>)>) -> (H256, MemoryDB<Blake2Hasher>) {
 		let mut changes_root = H256::default();
-		let mut changes_trie_update = MemoryDB::<Blake2Hasher>::default();		// TODO: change to new() to make more correct
+		let mut changes_trie_update = MemoryDB::<Blake2Hasher>::default();
 		{
 			let mut trie = TrieDBMut::<Blake2Hasher>::new(
 				&mut changes_trie_update,

substrate/core/client/db/src/light.rs

@@ -341,7 +341,6 @@ impl<Block> LightBlockchainStorage<Block> for LightStorage<Block>
 					// update block number to hash lookup entries.
 					for retracted in tree_route.retracted() {
 						if retracted.hash == meta.finalized_hash {
-							// TODO: can we recover here?
 							warn!("Safety failure: reverting finalized block {:?}",
 								(&retracted.number, &retracted.hash));
 						}
@@ -438,7 +437,6 @@ impl<Block> LightBlockchainStorage<Block> for LightStorage<Block>
 	fn finalize_header(&self, id: BlockId<Block>) -> ClientResult<()> {
 		if let Some(header) = self.header(id)? {
 			let mut transaction = DBTransaction::new();
-			// TODO: ensure best chain contains this block.
 			let hash = header.hash();
 			let number = *header.number();
 			self.note_finalized(&mut transaction, &header, hash.clone())?;

substrate/core/client/db/src/storage_cache.rs

@@ -45,7 +45,7 @@ pub type SharedCache<B, H> = Arc<Mutex<Cache<B, H>>>;
 
 /// Create new shared cache instance with given max memory usage.
 pub fn new_shared_cache<B: Block, H: Hasher>(shared_cache_size: usize) -> SharedCache<B, H> {
-	let cache_items = shared_cache_size / 100; // Estimated average item size. TODO: more accurate tracking
+	let cache_items = shared_cache_size / 100; // Guestimate, potentially inaccurate
 	Arc::new(Mutex::new(Cache {
 		storage: LruCache::new(cache_items),
 		hashes: LruCache::new(cache_items),

substrate/core/client/src/call_executor.rs

@@ -205,7 +205,6 @@ where
 		native_call: Option<NC>,
 	) -> Result<NativeOrEncoded<R>, error::Error> where ExecutionManager<EM>: Clone {
 		let state = self.backend.state_at(*at)?;
-		//TODO: Find a better way to prevent double block initialization
 		if method != "Core_initialise_block" && initialised_block.map(|id| id != *at).unwrap_or(true) {
 			let header = prepare_environment_block()?;
 			state_machine::execute_using_consensus_failure_handler::<

substrate/core/client/src/client.rs

@@ -130,7 +130,6 @@ pub trait BlockBody<Block: BlockT> {
 }
 
 /// Client info
-// TODO: split queue info from chain info and amalgamate into single struct.
 #[derive(Debug)]
 pub struct ClientInfo<Block: BlockT> {
 	/// Best block hash.
@@ -325,7 +324,6 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 
 	/// Get the RuntimeVersion at a given block.
 	pub fn runtime_version_at(&self, id: &BlockId<Block>) -> error::Result<RuntimeVersion> {
-		// TODO: Post Poc-2 return an error if version is missing
 		self.executor.runtime_version(id)
 	}
 
@@ -738,11 +736,9 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 			self.apply_finality_with_block_hash(operation, parent_hash, None, last_best, make_notifications)?;
 		}
 
-		// TODO: correct path logic for when to execute this function
-		// https://github.com/paritytech/substrate/issues/1232
+		// FIXME #1232: correct path logic for when to execute this function
 		let (storage_update,changes_update,storage_changes) = self.block_execution(&operation.op, &import_headers, origin, hash, body.clone())?;
 
-		// TODO: non longest-chain rule.
 		let is_new_best = finalized || match fork_choice {
 			ForkChoiceStrategy::LongestChain => import_headers.post().number() > &last_best_number,
 			ForkChoiceStrategy::Custom(v) => v,
@@ -880,7 +876,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 		// if the block is not a direct ancestor of the current best chain,
 		// then some other block is the common ancestor.
 		if route_from_best.common_block().hash != block {
-			// TODO: reorganize best block to be the best chain containing
+			// FIXME: #1442 reorganize best block to be the best chain containing
 			// `block`.
 		}
 
@@ -1020,7 +1016,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 
 	/// Get block status.
 	pub fn block_status(&self, id: &BlockId<Block>) -> error::Result<BlockStatus> {
-		// TODO: more efficient implementation
+		// this can probably be implemented more efficiently
 		if let BlockId::Hash(ref h) = id {
 			if self.importing_block.read().as_ref().map_or(false, |importing| h == importing) {
 				return Ok(BlockStatus::Queued);
@@ -1073,10 +1069,9 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 	/// If `maybe_max_block_number` is `Some(max_block_number)`
 	/// the search is limited to block `numbers <= max_block_number`.
 	/// in other words as if there were no blocks greater `max_block_number`.
-	///
-	/// TODO [snd] possibly implement this on blockchain::Backend and just redirect here
+	/// TODO : we want to move this implement to `blockchain::Backend`, see [#1443](https://github.com/paritytech/substrate/issues/1443)
 	/// Returns `Ok(None)` if `target_hash` is not found in search space.
-	/// TODO [snd] write down time complexity
+	/// TODO: document time complexity of this, see [#1444](https://github.com/paritytech/substrate/issues/1444)
 	pub fn best_containing(&self, target_hash: Block::Hash, maybe_max_number: Option<NumberFor<Block>>)
 		-> error::Result<Option<Block::Hash>>
 	{
@@ -1140,7 +1135,6 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 			// waiting until we are <= max_number
 			if let Some(max_number) = maybe_max_number {
 				loop {
-					// TODO [snd] this should be a panic
 					let current_header = self.backend.blockchain().header(BlockId::Hash(current_hash.clone()))?
 						.ok_or_else(|| error::Error::from(format!("failed to get header for hash {}", current_hash)))?;
 
@@ -1160,7 +1154,6 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 					return Ok(Some(best_hash));
 				}
 
-				// TODO [snd] this should be a panic
 				let current_header = self.backend.blockchain().header(BlockId::Hash(current_hash.clone()))?
 					.ok_or_else(|| error::Error::from(format!("failed to get header for hash {}", current_hash)))?;
 
@@ -1176,8 +1169,7 @@ impl<B, E, Block, RA> Client<B, E, Block, RA> where
 		// header may be on a dead fork -- the only leaves that are considered are
 		// those which can still be finalized.
 		//
-		// TODO: only issue this warning when not on a dead fork
-		// part of https://github.com/paritytech/substrate/issues/1558
+		// FIXME #1558 only issue this warning when not on a dead fork
 		warn!(
 			"Block {:?} exists in chain but not found when following all \
 			leaves backwards. Number limit = {:?}",

substrate/core/client/src/light/blockchain.rs

@@ -141,7 +141,7 @@ impl<S, F, Block> BlockchainHeaderBackend<Block> for Blockchain<S, F> where Bloc
 
 impl<S, F, Block> BlockchainBackend<Block> for Blockchain<S, F> where Block: BlockT, S: Storage<Block>, F: Fetcher<Block> {
 	fn body(&self, _id: BlockId<Block>) -> ClientResult<Option<Vec<Block::Extrinsic>>> {
-		// TODO [light]: fetch from remote node
+		// TODO: #1445 fetch from remote node
 		Ok(None)
 	}
 

substrate/core/consensus/aura/src/lib.rs

@@ -392,7 +392,7 @@ enum CheckedHeader<H> {
 /// check a header has been signed by the right key. If the slot is too far in the future, an error will be returned.
 /// if it's successful, returns the pre-header, the slot number, and the signat.
 //
-// FIXME: needs misbehavior types - https://github.com/paritytech/substrate/issues/1018
+// FIXME #1018 needs misbehavior types
 fn check_header<B: Block>(slot_now: u64, mut header: B::Header, hash: B::Hash, authorities: &[Ed25519AuthorityId])
 	-> Result<CheckedHeader<B::Header>, String>
 	where DigestItemFor<B>: CompatibleDigestItem
@@ -537,8 +537,7 @@ impl<B: Block, C, E> Verifier<B> for AuraVerifier<C, E> where
 		);
 
 		// we add one to allow for some small drift.
-		// FIXME: in the future, alter this queue to allow deferring of headers
-		// https://github.com/paritytech/substrate/issues/1019
+		// FIXME #1019 in the future, alter this queue to allow deferring of headers
 		let checked_header = check_header::<B>(slot_now + 1, header, hash, &authorities[..])?;
 		match checked_header {
 			CheckedHeader::Checked(pre_header, slot_num, sig) => {
@@ -577,7 +576,7 @@ impl<B: Block, C, E> Verifier<B> for AuraVerifier<C, E> where
 					fork_choice: ForkChoiceStrategy::LongestChain,
 				};
 
-				// FIXME: extract authorities - https://github.com/paritytech/substrate/issues/1019
+				// FIXME #1019 extract authorities
 				Ok((import_block, None))
 			}
 			CheckedHeader::Deferred(a, b) => {

substrate/core/consensus/common/src/import_queue.rs

@@ -401,7 +401,7 @@ pub fn import_single_block<B: BlockT, V: Verifier<B>>(
 			} else {
 				debug!(target: "sync", "Header {} was not provided ", block.hash);
 			}
-			return Err(BlockImportError::IncompleteHeader(peer)) //TODO: use persistent ID
+			return Err(BlockImportError::IncompleteHeader(peer))
 		},
 	};
 
@@ -441,7 +441,7 @@ pub fn import_single_block<B: BlockT, V: Verifier<B>>(
 		},
 		Ok(ImportResult::KnownBad) => {
 			debug!(target: "sync", "Peer gave us a bad block {}: {:?}", number, hash);
-			Err(BlockImportError::BadBlock(peer)) //TODO: use persistent ID
+			Err(BlockImportError::BadBlock(peer))
 		},
 		Err(e) => {
 			debug!(target: "sync", "Error importing block {}: {:?}: {:?}", number, hash, e);

substrate/core/consensus/rhd/src/lib.rs

@@ -31,7 +31,7 @@
 //! set for this block height.
 
 #![cfg(feature="rhd")]
-// FIXME: doesn't compile - https://github.com/paritytech/substrate/issues/1020
+// FIXME #1020 doesn't compile
 
 use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
@@ -432,7 +432,6 @@ impl<B, P, I, InStream, OutSink> Drop for BftFuture<B, P, I, InStream, OutSink>
 	OutSink: Sink<SinkItem=Communication<B>, SinkError=Error>,
 {
 	fn drop(&mut self) {
-		// TODO: have a trait member to pass misbehavior reports into.
 		let misbehavior = self.inner.drain_misbehavior().collect::<Vec<_>>();
 		self.inner.context().proposer.import_misbehavior(misbehavior);
 	}
@@ -466,7 +465,7 @@ pub struct BftService<B: Block, P, I> {
 	live_agreement: Mutex<Option<(B::Header, AgreementHandle)>>,
 	round_cache: Arc<Mutex<RoundCache<B::Hash>>>,
 	round_timeout_multiplier: u64,
-	key: Arc<ed25519::Pair>, // TODO: key changing over time.
+	key: Arc<ed25519::Pair>,
 	factory: P,
 }
 
@@ -488,14 +487,13 @@ impl<B, P, I> BftService<B, P, I>
 				start_round: 0,
 			})),
 			round_timeout_multiplier: 10,
-			key: key, // TODO: key changing over time.
+			key: key,
 			factory,
 		}
 	}
 
 	/// Get the local Authority ID.
 	pub fn local_id(&self) -> AuthorityId {
-		// TODO: based on a header and some keystore.
 		self.key.public().into()
 	}
 
@@ -1084,7 +1082,6 @@ impl<C, A> BaseProposer<<C as AuthoringApi>::Block> for Proposer<C, A> where
 				self.transaction_pool.ready(|pending_iterator| {
 					let mut pending_size = 0;
 					for pending in pending_iterator {
-						// TODO [ToDr] Probably get rid of it, and validate in runtime.
 						let encoded_size = pending.data.encode().len();
 						if pending_size + encoded_size >= MAX_TRANSACTIONS_SIZE { break }
 

substrate/core/executor/src/native_executor.rs

@@ -268,7 +268,6 @@ macro_rules! native_executor_instance {
 		native_executor_instance!(IMPL $name, $dispatcher, $version, $code);
 	};
 	(IMPL $name:ident, $dispatcher:path, $version:path, $code:expr) => {
-		// TODO: this is not so great – I think I should go back to have dispatch take a type param and modify this macro to accept a type param and then pass it in from the test-client instead
 		use primitives::Blake2Hasher as _Blake2Hasher;
 		impl $crate::NativeExecutionDispatch for $name {
 			fn native_equivalent() -> &'static [u8] {

substrate/core/executor/src/wasm_executor.rs

@@ -118,7 +118,6 @@ impl ReadPrimitive<u32> for MemoryInstance {
 	}
 }
 
-// TODO: this macro does not support `where` clauses and that seems somewhat tricky to add
 impl_function_executor!(this: FunctionExecutor<'e, E>,
 	ext_print_utf8(utf8_data: *const u8, utf8_len: u32) => {
 		if let Ok(utf8) = this.memory.get(utf8_data, utf8_len as usize) {

substrate/core/finality-grandpa/src/lib.rs

@@ -577,7 +577,6 @@ impl<B, E, Block: BlockT<Hash=H256>, N, RA> voter::Environment<Block::Hash, Numb
 		let prevote_timer = Delay::new(now + self.config.gossip_duration * 2);
 		let precommit_timer = Delay::new(now + self.config.gossip_duration * 4);
 
-		// TODO: dispatch this with `mpsc::spawn`.
 		let incoming = ::communication::checked_message_stream::<Block, _>(
 			round,
 			self.set_id,
@@ -857,7 +856,7 @@ fn finalize_block<B, Block: BlockT<Hash=H256>, E, RA>(
 	// lock must be held through writing to DB to avoid race
 	let mut authority_set = authority_set.inner().write();
 
-	// TODO [andre]: clone only when changed (#1483)
+	// FIXME #1483: clone only when changed
 	let old_authority_set = authority_set.clone();
 	// needed in case there is an authority set change, used for reverting in
 	// case of error

substrate/core/keystore/src/lib.rs

@@ -58,7 +58,7 @@ pub struct InvalidPassword;
 struct EncryptedKey {
 	mac: [u8; 32],
 	salt: [u8; 32],
-	ciphertext: Vec<u8>, // TODO: switch to fixed-size when serde supports
+	ciphertext: Vec<u8>, // FIXME: switch to fixed-size when serde supports
 	iv: [u8; 16],
 	iterations: u32,
 }

substrate/core/network/src/consensus_gossip.rs

@@ -76,7 +76,6 @@ impl<B: BlockT> ConsensusGossip<B> {
 		if roles.intersects(Roles::AUTHORITY) {
 			trace!(target:"gossip", "Registering {:?} {}", roles, who);
 			// Send out all known messages to authorities.
-			// TODO: limit by size
 			let mut known_messages = HashSet::new();
 			for entry in self.messages.iter() {
 				known_messages.insert((entry.topic, entry.message_hash));

substrate/core/network/src/on_demand.rs

@@ -213,7 +213,7 @@ impl<B, E> OnDemandService<B> for OnDemand<B, E> where
 	B::Header: HeaderT,
 {
 	fn on_connect(&self, peer: NodeIndex, role: Roles, best_number: NumberFor<B>) {
-		if !role.intersects(Roles::FULL | Roles::AUTHORITY) { // TODO: correct?
+		if !role.intersects(Roles::FULL | Roles::AUTHORITY) {
 			return;
 		}
 

substrate/core/network/src/protocol.rs

@@ -458,7 +458,6 @@ impl<B: BlockT, S: NetworkSpecialization<B>, H: ExHashT> Protocol<B, S, H> {
 			message::FromBlock::Number(n) => BlockId::Number(n),
 		};
 		let max = cmp::min(request.max.unwrap_or(u32::max_value()), MAX_BLOCK_DATA_RESPONSE) as usize;
-		// TODO: receipts, etc.
 		let get_header = request.fields.contains(message::BlockAttributes::HEADER);
 		let get_body = request.fields.contains(message::BlockAttributes::BODY);
 		let get_justification = request.fields.contains(message::BlockAttributes::JUSTIFICATION);
@@ -498,7 +497,6 @@ impl<B: BlockT, S: NetworkSpecialization<B>, H: ExHashT> Protocol<B, S, H> {
 	}
 
 	fn on_block_response(&self, io: &mut SyncIo, peer: NodeIndex, request: message::BlockRequest<B>, response: message::BlockResponse<B>) {
-		// TODO: validate response
 		let blocks_range = match (
 				response.blocks.first().and_then(|b| b.header.as_ref().map(|h| h.number())),
 				response.blocks.last().and_then(|b| b.header.as_ref().map(|h| h.number())),

substrate/core/primitives/src/changes_trie.rs

@@ -49,7 +49,7 @@ impl ChangesTrieConfiguration {
 			return 1;
 		}
 
-		// TODO: use saturating_pow when available
+		// FIXME: use saturating_pow once stabilized  - https://github.com/rust-lang/rust/issues/48320
 		let mut max_digest_interval = self.digest_interval;
 		for _ in 1..self.digest_levels {
 			max_digest_interval = match max_digest_interval.checked_mul(self.digest_interval) {

substrate/core/primitives/src/ed25519.rs

@@ -238,16 +238,6 @@ impl Pair {
 		r.copy_from_slice(pk);
 		Public(r)
 	}
-
-	/// Derive a child key. Probably unsafe and broken.
-	// TODO: proper HD derivation https://cardanolaunch.com/assets/Ed25519_BIP.pdf
-	pub fn derive_child_probably_bad(&self, chain_data: &[u8]) -> Pair {
-		let sig = self.sign(chain_data);
-		let mut seed = [0u8; 32];
-		seed.copy_from_slice(&sig[..32]);
-
-		Pair::from_seed(&seed)
-	}
 }
 
 /// Verify a signature on a message. Returns true if the signature is good.
@@ -350,12 +340,6 @@ mod test {
 		assert_eq!(pair1.public(), pair2.public());
 	}
 
-	#[test]
-	fn derive_child() {
-		let pair = Pair::generate();
-		let _pair2 = pair.derive_child_probably_bad(b"session_1234");
-	}
-
 	#[test]
 	fn ss58check_roundtrip_works() {
 		let pair = Pair::from_seed(b"12345678901234567890123456789012");

substrate/core/rpc/src/chain/number.rs

@@ -41,7 +41,8 @@ impl<Number: traits::As<u64>> NumberOrHex<Number> {
 		match self {
 			NumberOrHex::Number(n) => Ok(n),
 			NumberOrHex::Hex(h) => {
-				// TODO [ToDr] this only supports `u64` since `BlockNumber` is `As<u64>` we could possibly go with `u128`. (#1377)
+				// FIXME #1377 this only supports `u64` since `BlockNumber`
+				// is `As<u64>` we could possibly go with `u128`.
 				let l = h.low_u64();
 				if U256::from(l) != h {
 					Err(format!("`{}` does not fit into the block number type.", h))

substrate/core/service/src/chain_ops.rs

@@ -106,7 +106,7 @@ pub fn import_blocks<F, E, R>(
 	impl<B: Block> Link<B> for DummyLink { }
 
 	let client = new_client::<F>(&config)?;
-	// FIXME: this shouldn't need a mutable config. https://github.com/paritytech/substrate/issues/1134
+	// FIXME #1134 this shouldn't need a mutable config.
 	let queue = components::FullComponents::<F>::build_import_queue(&mut config, client.clone())?;
 	queue.start(DummyLink)?;
 

substrate/core/service/src/components.rs

@@ -217,7 +217,6 @@ impl<C: Components> MaintainTransactionPool<Self> for C where
 	ComponentClient<C>: ProvideRuntimeApi,
 	<ComponentClient<C> as ProvideRuntimeApi>::Api: TaggedTransactionQueue<ComponentBlock<C>>,
 {
-	// TODO [ToDr] Optimize and re-use tags from the pool.
 	fn on_block_imported(
 		id: &BlockId<ComponentBlock<C>>,
 		client: &ComponentClient<C>,
@@ -329,7 +328,7 @@ pub trait Components: Sized + 'static {
 	type RuntimeApi: Send + Sync;
 	/// A type that can start the RPC.
 	type RPC: StartRPC<Self>;
-	// TODO [ToDr] Traitify transaction pool and allow people to implement their own. (#1242)
+	// TODO: Traitify transaction pool and allow people to implement their own. (#1242)
 	/// A type that can maintain transaction pool.
 	type TransactionPool: MaintainTransactionPool<Self>;
 	/// Extrinsic pool type.

substrate/core/service/src/lib.rs

@@ -137,7 +137,7 @@ impl<Components: components::Components> Service<Components> {
 		let mut keystore = Keystore::open(config.keystore_path.as_str().into())?;
 
 		// This is meant to be for testing only
-		// FIXME: remove this - https://github.com/paritytech/substrate/issues/1063
+		// FIXME #1063 remove this
 		for seed in &config.keys {
 			keystore.generate_from_seed(seed)?;
 		}
@@ -274,7 +274,6 @@ impl<Components: components::Components> Service<Components> {
 			// extrinsic notifications
 			let network = Arc::downgrade(&network);
 			let events = transaction_pool.import_notification_stream()
-				// TODO [ToDr] Consider throttling?
 				.for_each(move |_| {
 					if let Some(network) = network.upgrade() {
 						network.trigger_repropagate();

substrate/core/sr-io/with_std.rs

@@ -41,7 +41,6 @@ use primitives::hexdisplay::HexDisplay;
 use primitives::H256;
 use hash_db::Hasher;
 
-// TODO: use the real error, not NoError.
 
 environmental!(ext: trait Externalities<Blake2Hasher>);
 

substrate/core/sr-io/without_std.rs

@@ -315,8 +315,6 @@ pub fn trie_root<
 	B: AsRef<[u8]>,
 >(_input: I) -> [u8; 32] {
 	unimplemented!()
-	// TODO Maybe implement (though probably easier/cleaner to have blake2 be the only thing
-	// implemneted natively and compile the trie logic as wasm).
 }
 
 /// A trie root formed from the enumerated items.
@@ -326,8 +324,6 @@ pub fn ordered_trie_root<
 	A: AsRef<[u8]>
 >(_input: I) -> [u8; 32] {
 	unimplemented!()
-	// TODO Maybe implement (though probably easier/cleaner to have blake2 be the only thing
-	// implemneted natively and compile the trie logic as wasm).
 }
 
 /// The current relay chain identifier.

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

@@ -156,7 +156,6 @@ impl<Address: Codec, Index: HasCompact + Codec, Signature: Codec, Call: Encode>
 	}
 }
 
-/// TODO: use derive when possible.
 #[cfg(feature = "std")]
 impl<Address, Index, Signature, Call> fmt::Debug
 	for UncheckedExtrinsic<Address, Index, Call, Signature>

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

@@ -168,7 +168,6 @@ impl<Address: Encode, Index, Signature: Encode, Call: Encode> serde::Serialize
 	}
 }
 
-/// TODO: use derive when possible.
 #[cfg(feature = "std")]
 impl<Address, Index, Call, Signature> fmt::Debug for UncheckedMortalCompactExtrinsic<Address, Index, Call, Signature> where
 	Address: fmt::Debug,

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

@@ -166,7 +166,6 @@ impl<Address: Encode, Index: Encode, Signature: Encode, Call: Encode> serde::Ser
 	}
 }
 
-/// TODO: use derive when possible.
 #[cfg(feature = "std")]
 impl<Address, Index, Call, Signature> fmt::Debug for UncheckedMortalExtrinsic<Address, Index, Call, Signature> where
 	Address: fmt::Debug,

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

@@ -579,7 +579,6 @@ mod tests {
 		pub enum RawLog<AuthorityId> { B1(AuthorityId), B2(AuthorityId) }
 	}
 
-	// TODO try to avoid redundant brackets: a(AuthoritiesChange), b
 	impl_outer_log! {
 		pub enum Log(InternalLog: DigestItem<H256, u64>) for Runtime {
 			a(AuthoritiesChange), b()

substrate/core/state-db/src/noncanonical.rs

@@ -220,7 +220,7 @@ impl<BlockHash: Hash, Key: Hash> NonCanonicalOverlay<BlockHash, Key> {
 				commit.data.inserted = self.last_canonicalized_overlay.iter().map(|(k, v)| (k.clone(), v.clone())).collect();
 				commit.data.deleted = overlay.deleted;
 			} else {
-				// TODO: borrow checker won't allow us to split out mutable references
+				// borrow checker won't allow us to split out mutable references
 				// required for recursive processing. A more efficient implementation
 				// that does not require converting to vector is possible
 				let mut vec: Vec<_> = self.levels.drain(..).collect();

substrate/core/state-machine/src/backend.rs

@@ -118,7 +118,7 @@ impl<H: Hasher> Consolidate for MemoryDB<H> {
 }
 
 /// Error impossible.
-// TODO: use `!` type when stabilized.
+// FIXME: use `!` type when stabilized. https://github.com/rust-lang/rust/issues/35121
 #[derive(Debug)]
 pub enum Void {}
 
@@ -291,7 +291,7 @@ impl<H: Hasher> Backend<H> for InMemory<H> where H::Out: HeapSizeOf {
 	}
 
 	fn try_into_trie_backend(self) -> Option<TrieBackend<Self::TrieBackendStorage, H>> {
-		let mut mdb = MemoryDB::default();	// TODO: should be more correct and use ::new()
+		let mut mdb = MemoryDB::default();
 		let mut root = None;
 		for (storage_key, map) in self.inner {
 			if storage_key != None {

substrate/core/state-machine/src/changes_trie/changes_iterator.rs

@@ -104,7 +104,7 @@ pub fn key_changes_proof_check<S: RootsStorage<H>, H: Hasher>(
 	max: u64,
 	key: &[u8]
 ) -> Result<Vec<(u64, u32)>, String> where H::Out: HeapSizeOf {
-	let mut proof_db = MemoryDB::<H>::default();	// TODO: use new for correctness
+	let mut proof_db = MemoryDB::<H>::default();
 	for item in proof {
 		proof_db.insert(&item);
 	}

substrate/core/state-machine/src/changes_trie/prune.rs

@@ -62,7 +62,7 @@ pub fn prune<S: Storage<H>, H: Hasher, F: FnMut(H::Out)>(
 	};
 
 	// delete changes trie for every block in range
-	// TODO: limit `max_digest_interval` so that this cycle won't involve huge ranges
+	// FIXME: limit `max_digest_interval` so that this cycle won't involve huge ranges
 	for block in first..last+1 {
 		let root = match storage.root(current_block, block) {
 			Ok(Some(root)) => root,

substrate/core/state-machine/src/ext.rs

@@ -302,7 +302,7 @@ where
 		);
 		let root_and_tx = root_and_tx.map(|(root, changes)| {
 			let mut calculated_root = Default::default();
-			let mut mdb = MemoryDB::default();	// TODO: use new for correctness
+			let mut mdb = MemoryDB::default();
 			{
 				let mut trie = TrieDBMut::<H>::new(&mut mdb, &mut calculated_root);
 				for (key, value) in changes {

substrate/core/state-machine/src/proving_backend.rs

@@ -195,7 +195,7 @@ where
 	H: Hasher,
 	H::Out: HeapSizeOf,
 {
-	let mut db = MemoryDB::default();	// TODO: use new for correctness
+	let mut db = MemoryDB::default();
 	for item in proof {
 		db.insert(&item);
 	}

substrate/core/state-machine/src/trie_backend.rs

@@ -82,7 +82,7 @@ impl<S: TrieBackendStorage<H>, H: Hasher> Backend<H> for TrieBackend<S, H> where
 	}
 
 	fn pairs(&self) -> Vec<(Vec<u8>, Vec<u8>)> {
-		let mut read_overlay = MemoryDB::default();	// TODO: use new for correctness
+		let mut read_overlay = MemoryDB::default();
 		let eph = Ephemeral::new(self.essence.backend_storage(), &mut read_overlay);
 
 		let collect_all = || -> Result<_, Box<TrieError<H::Out>>> {
@@ -106,7 +106,7 @@ impl<S: TrieBackendStorage<H>, H: Hasher> Backend<H> for TrieBackend<S, H> where
 	}
 
 	fn keys(&self, prefix: &Vec<u8>) -> Vec<Vec<u8>> {
-		let mut read_overlay = MemoryDB::default();	// TODO: use new for correctness
+		let mut read_overlay = MemoryDB::default();
 		let eph = Ephemeral::new(self.essence.backend_storage(), &mut read_overlay);
 
 		let collect_all = || -> Result<_, Box<TrieError<H::Out>>> {
@@ -193,7 +193,7 @@ pub mod tests {
 
 	fn test_db() -> (MemoryDB<Blake2Hasher>, H256) {
 		let mut root = H256::default();
-		let mut mdb = MemoryDB::<Blake2Hasher>::default();	// TODO: use new() to be more correct
+		let mut mdb = MemoryDB::<Blake2Hasher>::default();
 		{
 			let mut trie = TrieDBMut::new(&mut mdb, &mut root);
 			trie.insert(b"key", b"value").expect("insert failed");
@@ -230,7 +230,7 @@ pub mod tests {
 	#[test]
 	fn pairs_are_empty_on_empty_storage() {
 		assert!(TrieBackend::<MemoryDB<Blake2Hasher>, Blake2Hasher>::new(
-			MemoryDB::default(),	// TODO: use new() to be more correct
+			MemoryDB::default(),
 			Default::default(),
 		).pairs().is_empty());
 	}

substrate/core/state-machine/src/trie_backend_essence.rs

@@ -176,7 +176,7 @@ impl<'a,
 	where H::Out: HeapSizeOf
 {
 	fn keys(&self) -> HashMap<H::Out, i32> {
-		self.overlay.keys() // TODO: iterate backing
+		self.overlay.keys()
 	}
 
 	fn get(&self, key: &H::Out) -> Option<DBValue> {

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

@@ -49,7 +49,7 @@ use keyring::Keyring;
 mod local_executor {
 	#![allow(missing_docs)]
 	use super::runtime;
-	// TODO: change the macro and pass in the `BlakeHasher` that dispatch needs from here instead
+	// FIXME #1576 change the macro and pass in the `BlakeHasher` that dispatch needs from here instead
 	native_executor_instance!(
 		pub LocalExecutor,
 		runtime::api::dispatch,

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

@@ -20,9 +20,6 @@
 //! and their priority.
 //! The pool is able to return an iterator that traverses transaction
 //! graph in the correct order taking into account priorities and dependencies.
-//!
-//! TODO [ToDr]
-//! - [ ] Multi-threading (getting ready transactions should not block the pool)
 
 #![warn(missing_docs)]
 #![warn(unused_extern_crates)]

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

@@ -307,7 +307,6 @@ impl<B: ChainApi> Pool<B> {
 
 impl<B: ChainApi> Pool<B> {
 	/// Create a new transaction pool.
-	/// TODO [ToDr] Options
 	pub fn new(_options: Options, api: B) -> Self {
 		Pool {
 			api,

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

@@ -67,7 +67,6 @@ impl<T, Block> txpool::ChainApi for ChainApi<T, Block> where
 		Ok(self.client.runtime_api().validate_transaction(at, uxt)?)
 	}
 
-	// TODO [toDr] Use proper lbock number type
 	fn block_id_to_number(&self, at: &BlockId<Self::Block>) -> error::Result<Option<txpool::NumberFor<Self>>> {
 		Ok(self.client.block_number_from_id(at)?)
 	}

substrate/core/trie/src/lib.rs

@@ -16,7 +16,7 @@
 
 //! Utility functions to interact with Substrate's Base-16 Modified Merkle Patricia tree ("trie").
 
-// TODO: no_std
+// FIXME: no_std - https://github.com/paritytech/substrate/issues/1574
 
 mod error;
 mod node_header;
@@ -71,7 +71,7 @@ pub fn delta_trie_root<H: Hasher, I, A, B>(db: &mut HashDB<H>, mut root: H::Out,
 		for (key, change) in delta {
 			match change {
 				Some(val) => trie.insert(key.as_ref(), val.as_ref())?,
-				None => trie.remove(key.as_ref())?, // TODO: archive mode
+				None => trie.remove(key.as_ref())?,
 			};
 		}
 	}
@@ -151,7 +151,7 @@ pub fn child_delta_trie_root<H: Hasher, I, A, B>(_storage_key: &[u8], db: &mut H
 		for (key, change) in delta {
 			match change {
 				Some(val) => trie.insert(key.as_ref(), val.as_ref())?,
-				None => trie.remove(key.as_ref())?, // TODO: archive mode
+				None => trie.remove(key.as_ref())?,
 			};
 		}
 	}

substrate/core/trie/src/node_codec.rs

@@ -95,14 +95,14 @@ impl<H: Hasher> trie_db::NodeCodec<H> for NodeCodec<H> {
 		vec![EMPTY_TRIE]
 	}
 
-	// TODO: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
+	// FIXME: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
 	fn leaf_node(partial: &[u8], value: &[u8]) -> Vec<u8> {
 		let mut output = partial_to_key(partial, LEAF_NODE_OFFSET, LEAF_NODE_BIG);
 		value.encode_to(&mut output);
 		output
 	}
 
-	// TODO: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
+	// FIXME: refactor this so that `partial` isn't already encoded with HPE. Should just be an `impl Iterator<Item=u8>`.
 	fn ext_node(partial: &[u8], child: ChildReference<H::Out>) -> Vec<u8> {
 		let mut output = partial_to_key(partial, EXTENSION_NODE_OFFSET, EXTENSION_NODE_BIG);
 		match child {

substrate/core/trie/src/trie_stream.rs

@@ -67,34 +67,25 @@ impl trie_root::TrieStream for TrieStream {
 
 	fn append_leaf(&mut self, key: &[u8], value: &[u8]) {
 		self.buffer.extend(fuse_nibbles_node(key, true));
-		// OPTIMISATION: I'd like to do `hpe.encode_to(&mut self.buffer);` here; need an `impl<'a> Encode for impl Iterator<Item = u8> + 'a`?
 		value.encode_to(&mut self.buffer);
 	}
 	fn begin_branch(&mut self, maybe_value: Option<&[u8]>, has_children: impl Iterator<Item = bool>) {
-//		println!("[begin_branch] pushing BRANCH_NODE");
 		self.buffer.extend(&branch_node(maybe_value.is_some(), has_children));
 		// Push the value if one exists.
 		if let Some(value) = maybe_value {
 			value.encode_to(&mut self.buffer);
 		}
-//		println!("[begin_branch] buffer so far: {:#x?}", self.buffer);
 	}
 	fn append_extension(&mut self, key: &[u8]) {
 		self.buffer.extend(fuse_nibbles_node(key, false));
 	}
 	fn append_substream<H: Hasher>(&mut self, other: Self) {
 		let data = other.out();
-//		println!("[append_substream] START own buffer: {:x?}", self.buffer);
-//		println!("[append_substream] START other buffer: {:x?}", data);
 		match data.len() {
 			0...31 => {
-//				println!("[append_substream] appending data, because data.len() = {}", data.len());
 				data.encode_to(&mut self.buffer)
 			},
 			_ => {
-//				println!("[append_substream] would have hashed, because data.len() = {}", data.len());
-//				data.encode_to(&mut self.buffer)
-				// TODO: re-enable hashing before merging
 				H::hash(&data).as_ref().encode_to(&mut self.buffer)
 			}
 		}

substrate/node/cli/src/chain_spec.rs

@@ -58,7 +58,7 @@ fn staging_testnet_config_genesis() -> GenesisConfig {
 
 	GenesisConfig {
 		consensus: Some(ConsensusConfig {
-			code: include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/node_runtime.compact.wasm").to_vec(),    // TODO change
+			code: include_bytes!("../../runtime/wasm/target/wasm32-unknown-unknown/release/node_runtime.compact.wasm").to_vec(),    // FIXME change once we have #1252
 			authorities: initial_authorities.clone(),
 		}),
 		system: None,

substrate/node/cli/src/service.rs

@@ -46,8 +46,7 @@ construct_simple_protocol! {
 /// Node specific configuration
 pub struct NodeConfig<F: substrate_service::ServiceFactory> {
 	/// grandpa connection to import block
-	// FIXME: rather than putting this on the config, let's have an actual intermediate setup state
-	// https://github.com/paritytech/substrate/issues/1134
+	// FIXME #1134 rather than putting this on the config, let's have an actual intermediate setup state
 	pub grandpa_import_setup: Option<(Arc<grandpa::BlockImportForService<F>>, grandpa::LinkHalfForService<F>)>,
 	inherent_data_providers: InherentDataProviders,
 }
@@ -106,7 +105,7 @@ construct_service_factory! {
 				executor.spawn(grandpa::run_grandpa(
 					grandpa::Config {
 						local_key,
-						// FIXME: make this available through chainspec?
+						// FIXME #1578 make this available through chainspec
 						gossip_duration: Duration::new(4, 0),
 						justification_period: 4096,
 						name: Some(service.config.name.clone())

substrate/srml/consensus/src/lib.rs

@@ -201,7 +201,6 @@ decl_module! {
 		/// Report some misbehaviour.
 		fn report_misbehavior(origin, _report: Vec<u8>) {
 			ensure_signed(origin)?;
-			// TODO: requires extension trait.
 		}
 
 		/// Note the previous block's validator missed their opportunity to propose a block.

substrate/srml/contract/src/lib.rs

@@ -347,12 +347,8 @@ decl_storage! {
 	}
 }
 
-// TODO: consider storing upper-bound for contract's gas limit in fixed-length runtime
-// code in contract itself and use that.
-
 /// The storage items associated with an account/key.
 ///
-/// TODO: keys should also be able to take AsRef<KeyType> to ensure Vec<u8>s can be passed as &[u8]
 pub(crate) struct StorageOf<T>(rstd::marker::PhantomData<T>);
 impl<T: Trait> StorageDoubleMap for StorageOf<T> {
 	const PREFIX: &'static [u8] = b"con:sto:";

substrate/srml/contract/src/wasm/runtime.rs

@@ -196,8 +196,6 @@ fn write_sandbox_memory<T: Trait>(
 // * AFTER MAKING A CHANGE MAKE SURE TO UPDATE COMPLEXITY.MD *
 // ***********************************************************
 
-// TODO: ext_balance, ext_address, ext_callvalue, etc.
-
 // Define a function `fn init_env<E: Ext>() -> HostFunctionSet<E>` that returns
 // a function set which can be imported by an executed contract.
 define_env!(Env, <E: Ext>,

substrate/srml/grandpa/src/lib.rs

@@ -181,7 +181,7 @@ decl_module! {
 		/// Report some misbehaviour.
 		fn report_misbehavior(origin, _report: Vec<u8>) {
 			ensure_signed(origin)?;
-			// TODO: https://github.com/paritytech/substrate/issues/1112
+			// FIXME: https://github.com/paritytech/substrate/issues/1112
 		}
 
 		fn on_finalise(block_number: T::BlockNumber) {
@@ -259,7 +259,7 @@ impl<T: Trait> Module<T> where Ed25519AuthorityId: core::convert::From<<T as Tra
 /// sets should be.
 pub struct SyncedAuthorities<T>(::rstd::marker::PhantomData<T>);
 
-// TODO: remove when https://github.com/rust-lang/rust/issues/26925 is fixed
+// FIXME: remove when https://github.com/rust-lang/rust/issues/26925 is fixed
 impl<T> Default for SyncedAuthorities<T> {
 	fn default() -> Self {
 		SyncedAuthorities(::rstd::marker::PhantomData)

substrate/srml/session/src/lib.rs

@@ -138,7 +138,7 @@ decl_storage! {
 impl<T: Trait> Module<T> {
 	/// The number of validators currently.
 	pub fn validator_count() -> u32 {
-		<Validators<T>>::get().len() as u32	// TODO: can probably optimised
+		<Validators<T>>::get().len() as u32
 	}
 
 	/// The last length change, if there was one, zero if not.
@@ -158,7 +158,7 @@ impl<T: Trait> Module<T> {
 	/// Called by `staking::new_era()` only. `next_session` should be called after this in order to
 	/// update the session keys to the next validator set.
 	pub fn set_validators(new: &[T::AccountId]) {
-		<Validators<T>>::put(&new.to_vec());			// TODO: optimise.
+		<Validators<T>>::put(&new.to_vec());
 		<consensus::Module<T>>::set_authorities(
 			&new.iter().cloned().map(T::ConvertAccountIdToSessionKey::convert).collect::<Vec<_>>()
 		);

substrate/srml/staking/src/lib.rs

@@ -355,7 +355,7 @@ impl<T: Trait> Module<T> {
 			let noms = Self::current_nominators_for(v);
 			let total = noms.iter().map(<balances::Module<T>>::total_balance).fold(T::Balance::zero(), |acc, x| acc + x);
 			if !total.is_zero() {
-				let safe_mul_rational = |b| b * rem / total;// TODO: avoid overflow
+				let safe_mul_rational = |b| b * rem / total;// FIXME #1572 avoid overflow
 				for n in noms.iter() {
 					let _ = <balances::Module<T>>::slash(n, safe_mul_rational(<balances::Module<T>>::total_balance(n)));	// best effort - not much that can be done on fail.
 				}
@@ -376,7 +376,7 @@ impl<T: Trait> Module<T> {
 				.map(<balances::Module<T>>::total_balance)
 				.fold(<balances::Module<T>>::total_balance(who), |acc, x| acc + x)
 				.max(One::one());
-			let safe_mul_rational = |b| b * reward / total;// TODO: avoid overflow
+			let safe_mul_rational = |b| b * reward / total;// FIXME #1572:  avoid overflow
 			for n in noms.iter() {
 				let _ = <balances::Module<T>>::reward(n, safe_mul_rational(<balances::Module<T>>::total_balance(n)));
 			}
@@ -454,7 +454,7 @@ impl<T: Trait> Module<T> {
 		// combination of validators, then use session::internal::set_validators().
 		// for now, this just orders would-be stakers by their balances and chooses the top-most
 		// <ValidatorCount<T>>::get() of them.
-		// TODO: this is not sound. this should be moved to an off-chain solution mechanism.
+		// FIXME #1571 this is not sound. this should be moved to an off-chain solution mechanism.
 		let mut intentions = Self::intentions()
 			.into_iter()
 			.map(|v| (Self::slashable_balance(&v), v))

substrate/srml/staking/src/tests.rs

@@ -416,7 +416,6 @@ fn nominating_slashes_should_work() {
 		assert_eq!(Balances::total_balance(&2), 20);		//not slashed
 		assert_eq!(Balances::total_balance(&3), 10);		//slashed
 		assert_eq!(Balances::total_balance(&4), 30);		//slashed
-		// TODO: change slash % to something sensible.
 	});
 }
 

substrate/srml/support/procedural/src/storage/mod.rs

@@ -74,7 +74,7 @@ struct AddExtraGenesisLine {
 	pub extra_field: ext::Parens<Ident>,
 	pub coldot_token: Token![:],
 	pub extra_type: syn::Type,
-	// TODO use a custom ext::Option instead (syn option on '=' fails)
+	// FIXME #1570: use a custom ext::Option instead (syn option on '=' fails)
 	pub default_value: ext::Seq<DeclStorageDefault>,
 }
 
@@ -91,7 +91,7 @@ struct DeclStorageLine {
 	pub build: Option<DeclStorageBuild>,
 	pub coldot_token: Token![:],
 	pub storage_type: DeclStorageType,
-	// TODO use a custom ext::Option instead (syn option on '=' fails)
+	// FIXME #1570: use a custom ext::Option instead (syn option on '=' fails)
 	pub default_value: ext::Seq<DeclStorageDefault>,
 }
 

substrate/srml/support/procedural/tools/src/lib.rs

@@ -57,9 +57,7 @@ macro_rules! custom_keyword {
 }
 
 
-// TODO following functions are copied from sr-api-macros : do a merge to get a unique procedural
-// macro tooling crate (this crate path does not look good for it)
-
+// FIXME #1569, remove the following functions, which are copied from sr-api-macros
 use proc_macro2::{TokenStream, Span};
 use syn::Ident;
 

substrate/srml/support/src/dispatch.rs

@@ -485,7 +485,7 @@ macro_rules! decl_module {
 		// Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
 		#[derive(Clone, Copy, PartialEq, Eq)]
 		#[cfg_attr(feature = "std", derive(Debug))]
-		// TODO: switching based on std feature is because of an issue in
+		// FIXME: switching based on std feature is because of an issue in
 		// serde-derive for when we attempt to derive `Deserialize` on these types,
 		// in a situation where we've imported `srml_support` as another name.
 		#[cfg(feature = "std")]

substrate/srml/support/src/storage/generator.rs

@@ -194,7 +194,7 @@ pub trait StorageMap<K: codec::Codec, V: codec::Codec> {
 	fn mutate<R, F: FnOnce(&mut Self::Query) -> R, S: Storage>(key: &K, f: F, storage: &S) -> R;
 }
 
-// TODO: Remove this in favour of `decl_storage` macro.
+// FIXME #1466 Remove this in favour of `decl_storage` macro.
 /// Declares strongly-typed wrappers around codec-compatible types in storage.
 #[macro_export]
 macro_rules! storage_items {
@@ -445,7 +445,6 @@ macro_rules! __storage_items_internal {
 			}
 
 			/// Get the key used to put the length field.
-			// TODO: concat macro should accept byte literals.
 			fn len_key() -> $crate::rstd::vec::Vec<u8> {
 				let mut key = $prefix.to_vec();
 				key.extend(b"len");
@@ -513,7 +512,7 @@ macro_rules! __handle_wrap_internal {
 	};
 }
 
-// TODO: revisit this idiom once we get `type`s in `impl`s.
+// FIXME: revisit this idiom once we get `type`s in `impl`s.
 /*impl<T: Trait> Module<T> {
 	type Now = super::Now<T>;
 }*/

substrate/srml/support/src/storage/mod.rs

@@ -24,8 +24,6 @@ use codec::{Codec, Decode, KeyedVec, Input};
 #[macro_use]
 pub mod generator;
 
-// TODO: consider using blake256 to avoid possible preimage attack.
-
 struct IncrementalInput<'a> {
 	key: &'a [u8],
 	pos: usize,

substrate/srml/system/src/lib.rs

@@ -344,9 +344,9 @@ impl<T: Trait> Module<T> {
 	#[cfg(any(feature = "std", test))]
 	pub fn externalities() -> TestExternalities<Blake2Hasher> {
 		TestExternalities::new(map![
-			twox_128(&<BlockHash<T>>::key_for(T::BlockNumber::zero())).to_vec() => [69u8; 32].encode(),	// TODO: replace with Hash::default().encode
+			twox_128(&<BlockHash<T>>::key_for(T::BlockNumber::zero())).to_vec() => [69u8; 32].encode(),
 			twox_128(<Number<T>>::key()).to_vec() => T::BlockNumber::one().encode(),
-			twox_128(<ParentHash<T>>::key()).to_vec() => [69u8; 32].encode(),	// TODO: replace with Hash::default().encode
+			twox_128(<ParentHash<T>>::key()).to_vec() => [69u8; 32].encode(),
 			twox_128(<RandomSeed<T>>::key()).to_vec() => T::Hash::default().encode()
 		])
 	}