Make use of NLL in client crate (#1436)

* fix: set edition to 2018 in Cargo.toml.

* fix: refactor function to make use of NLL.

* fix: result of applying 'cargo fix --edition' command.

* fix: removes extern crate

* fix: remove module uses from lib.rs

* fix: tests imports

substrate/core/client/src/in_mem.rs

@@ -19,20 +19,20 @@
 use std::collections::HashMap;
 use std::sync::Arc;
 use parking_lot::RwLock;
-use error;
-use backend::{self, NewBlockState};
-use light;
+use crate::error;
+use crate::backend::{self, NewBlockState};
+use crate::light;
 use primitives::storage::well_known_keys;
 use runtime_primitives::generic::BlockId;
 use runtime_primitives::traits::{Block as BlockT, Header as HeaderT, Zero,
 	NumberFor, As, Digest, DigestItem, AuthorityIdFor};
 use runtime_primitives::{Justification, StorageMap, ChildrenStorageMap};
-use blockchain::{self, BlockStatus, HeaderBackend};
+use crate::blockchain::{self, BlockStatus, HeaderBackend};
 use state_machine::backend::{Backend as StateBackend, InMemory, Consolidate};
 use state_machine::InMemoryChangesTrieStorage;
 use hash_db::Hasher;
 use heapsize::HeapSizeOf;
-use leaves::LeafSet;
+use crate::leaves::LeafSet;
 use trie::MemoryDB;
 
 struct PendingBlock<B: BlockT> {
@@ -166,7 +166,7 @@ impl<Block: BlockT> Blockchain<Block> {
 		justification: Option<Justification>,
 		body: Option<Vec<<Block as BlockT>::Extrinsic>>,
 		new_state: NewBlockState,
-	) -> ::error::Result<()> {
+	) -> crate::error::Result<()> {
 		let number = header.number().clone();
 		let best_tree_route = match new_state.is_best() {
 			false => None,
@@ -175,7 +175,7 @@ impl<Block: BlockT> Blockchain<Block> {
 				if &best_hash == header.parent_hash() {
 					None
 				} else {
-					let route = ::blockchain::tree_route(
+					let route = crate::blockchain::tree_route(
 						self,
 						BlockId::Hash(best_hash),
 						BlockId::Hash(*header.parent_hash()),