Introduce inherent digests (#2466)

* Introduce inherent digests

* Implement inherent digests

* fix silly error

* Implementation of inherent digests in BABE

All tests pass. There are still limitations:

1. The runtime strips out inherent digests, so BABE must re-add them.
2. The test runtime checks that it can re-compute all digests.  It
   can’t, so I had to comment out that test.

* Fix compilation and seal import

Seals were not imported correctly: the pre-digest was imported twice,
instead of both it and the seal being imported.  Also, other parts of
the code did not compile due to incomplete refactoring.

* Remove bogus assertion

* Fix testsuite compilation

* Remove unused import

* Fix compiler diagnostics

* Add inherent digest parameters to block constructors

This enforces that inherent digests are added first.

* Fixup Cargo.lock

* Fix build errors

* Re-add an incorrectly removed import

* Bump primitive-types version

* Update Cargo.lock

* Refactoring

* Use inherent digests for AuRa

They do reach the runtime, but get stripped.  I have not figured out
where.

* Fix compilation errors

* Fix compilation errors due to incorrect types

* Fix whitespace

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Add preamble

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Fix silly compile error

* Refactor pre-digest finding code into a separate function

* Remove unwanted assertion

It is too likely to bring down the entire blockchain.

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Use `find_pre_digest` after runtime, too

Also, use `Member` trait rather than rolling our own requirements.

Suggested-by: Tomasz Drwiega <tomasz@parity.io>

* Fix various warnings

mostly due to upgrading the dependency on `error_chain`.

* Pre-digests nearly complete

This nearly completes the implementation of pre-runtime digests.

* `Seal2` → `Seal` and fix test suite

* Try to fix the storage error

* Try to fix storage (again)

* Fix tests

* Hopefully finish pre-runtime digests

The key is to pass *only* the pre-runtime digests to the runtime.  The
others must be stripped out by `initialize_block`.

* Fix silly typo

* Fix another silly mistake

* Remove unnecessary filtering of BABE pre-digests

We no longer get duplicate BABE pre-digests, so if they appear, the
header should be rejected outright.

* Update Cargo.lock files

* Reformatting

* Fix silly typo in inherent digest code

Also, revert `error.rs` files that contained calls to the `error_chain!`
macro.

* Try to keep the runtime from stripping pre-digests

Currently runs into the “Storage root must match that calculated”
assertion.

* Don’t compute storage root until storage changes are done.

Also, fix a compilation error.

* Fix compile-time error

* Fix compilation errors

* Fix more compile errors

* Hopefully it compiles this time…

* Fix compilation and add docs

* Prevent BABE from adding duplicate pre-runtime digests

Found by comparing with the AuRa code.  I also did some refactoring.

* Respond to review and fix some warnings

* Delete some dead code introduced earlier

* More dead code goes away

* `ref mut` → `&mut`

* Respond to review and fix some warnings

* Fix compilation error

* Remove unneeded `HashT` type parameter

Suggested-by: Robert Habermeier <robert@parity.io>

* Remove spurious #[allow(deprecated)]

* Document inherent digest parameter to `build_block`

* Delete `Simple` trait

It wasn’t needed

* delete wrongly added files

* Fix trait bounds

* Digest serialization tests

I also did some reformatting and cleanup.

* Apply suggestions from code review

Reformatting

Co-Authored-By: André Silva <andre.beat@gmail.com>

* Swap two arguments to `propose` and `propose_with`

Also, remove some needless unsafe code.

* Remove bogus `#![allow(deprecated)]` annotations

With the removal of the deprecated `Seal` variant, these are not needed.

* Add a missing `#[allow(deprecated)]` in the AuRa tests

* Fix silly compile error

* Fix silly compiler error

RLS did not tell me that I hadn’t fixed `babe/lib.rs`, so I missed it.

* Fixes made automatically by Cargo

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

@@ -117,7 +117,7 @@ impl<Block: BlockT> AuthoritySetForFinalityChecker<Block> for Arc<FetchChecker<B
 			call_data: vec![],
 			retry_count: None,
 		};
-		
+
 		self.check_execution_proof(&request, proof)
 			.and_then(|authorities| {
 				let authorities: Vec<(AuthorityId, u64)> = Decode::decode(&mut &authorities[..])

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

@@ -317,7 +317,7 @@ where
 					// for the canon block the new authority set should start
 					// with. we use the minimum between the median and the local
 					// best finalized block.
-					
+
 					#[allow(deprecated)]
 					let best_finalized_number = self.inner.backend().blockchain().info()
 						.map_err(|e| ConsensusError::ClientImport(e.to_string()))?

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

@@ -1067,7 +1067,7 @@ fn allows_reimporting_change_blocks() {
 	let (block_import, ..) = net.make_block_import(client.clone());
 
 	let full_client = client.as_full().unwrap();
-	let builder = full_client.new_block_at(&BlockId::Number(0)).unwrap();
+	let builder = full_client.new_block_at(&BlockId::Number(0), Default::default()).unwrap();
 	let block = builder.bake().unwrap();
 	api.scheduled_changes.lock().insert(*block.header.parent_hash(), ScheduledChange {
 		next_authorities: make_ids(peers_b),
@@ -1116,7 +1116,7 @@ fn test_bad_justification() {
 	let (block_import, ..) = net.make_block_import(client.clone());
 
 	let full_client = client.as_full().expect("only full clients are used in test");
-	let builder = full_client.new_block_at(&BlockId::Number(0)).unwrap();
+	let builder = full_client.new_block_at(&BlockId::Number(0), Default::default()).unwrap();
 	let block = builder.bake().unwrap();
 	api.scheduled_changes.lock().insert(*block.header.parent_hash(), ScheduledChange {
 		next_authorities: make_ids(peers_b),
@@ -1480,7 +1480,7 @@ fn empty_finality_proof_is_returned_to_light_client_when_authority_set_is_differ
 	runner_net.lock().add_light_peer(&GrandpaTestNet::default_config());
 	runner_net.lock().sync_without_disconnects();
 
- 	// check block, finalized on light client
+	// check block, finalized on light client
 	assert_eq!(
 		runner_net.lock().peer(3).client().info().unwrap().chain.finalized_number,
 		if FORCE_CHANGE { 0 } else { 10 },