remove trait bounds from several structs (#9055)

ethcore/src/cache_manager.rs

@@ -19,7 +19,7 @@ use std::hash::Hash;
 
 const COLLECTION_QUEUE_SIZE: usize = 8;
 
-pub struct CacheManager<T> where T: Eq + Hash {
+pub struct CacheManager<T> {
 	pref_cache_size: usize,
 	max_cache_size: usize,
 	bytes_per_cache_entry: usize,

ethcore/src/executive.rs

@@ -163,7 +163,7 @@ impl TransactOptions<trace::NoopTracer, trace::NoopVMTracer> {
 }
 
 /// Transaction executor.
-pub struct Executive<'a, B: 'a + StateBackend> {
+pub struct Executive<'a, B: 'a> {
 	state: &'a mut State<B>,
 	info: &'a EnvInfo,
 	machine: &'a Machine,

ethcore/src/externalities.rs

@@ -63,9 +63,7 @@ impl OriginInfo {
 }
 
 /// Implementation of evm Externalities.
-pub struct Externalities<'a, T: 'a, V: 'a, B: 'a>
-	where T: Tracer, V:  VMTracer, B: StateBackend
-{
+pub struct Externalities<'a, T: 'a, V: 'a, B: 'a> {
 	state: &'a mut State<B>,
 	env_info: &'a EnvInfo,
 	machine: &'a Machine,

ethcore/src/state/mod.rs

@@ -305,7 +305,7 @@ pub fn prove_transaction<H: AsHashDB<KeccakHasher> + Send + Sync>(
 /// checkpoint can be discarded with `discard_checkpoint`. All of the orignal
 /// backed-up values are moved into a parent checkpoint (if any).
 ///
-pub struct State<B: Backend> {
+pub struct State<B> {
 	db: B,
 	root: H256,
 	cache: RefCell<HashMap<Address, AccountEntry>>,

ethcore/types/src/account_diff.rs

@@ -24,7 +24,7 @@ use bytes::Bytes;
 
 #[derive(Debug, PartialEq, Eq, Clone)]
 /// Diff type for specifying a change (or not).
-pub enum Diff<T> where T: Eq {
+pub enum Diff<T> {
 	/// Both sides are the same.
 	Same,
 	/// Left (pre, source) side doesn't include value, right side (post, destination) does.
@@ -35,9 +35,15 @@ pub enum Diff<T> where T: Eq {
 	Died(T),
 }
 
-impl<T> Diff<T> where T: Eq {
+impl<T> Diff<T> {
 	/// Construct new object with given `pre` and `post`.
-	pub fn new(pre: T, post: T) -> Self { if pre == post { Diff::Same } else { Diff::Changed(pre, post) } }
+	pub fn new(pre: T, post: T) -> Self where T: Eq {
+		if pre == post {
+			Diff::Same
+		} else {
+			Diff::Changed(pre, post)
+		}
+	}
 
 	/// Get the before value, if there is one.
 	pub fn pre(&self) -> Option<&T> { match *self { Diff::Died(ref x) | Diff::Changed(ref x, _) => Some(x), _ => None } }