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Went through the TODOs, removed a bunch, which are outdated or nothing more than a regular comment, documented a bunch more as actual tickets and made them FIXMEs and unified their structure (`FIXME #TICKETNO DESC` for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/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)
 			}
 		}