Capture traces and write some tests.

ethcore/src/trace/executive_tracer.rs

@@ -83,6 +83,8 @@ fn should_prefix_address_properly() {
 }
 
 impl Tracer for ExecutiveTracer {
+	type Output = FlatTrace;
+
 	fn prepare_trace_call(&self, params: &ActionParams) -> Option<Call> {
 		Some(Call::from(params.clone()))
 	}
@@ -201,6 +203,8 @@ impl ExecutiveVMTracer {
 }
 
 impl VMTracer for ExecutiveVMTracer {
+	type Output = VMTrace;
+
 	fn trace_next_instruction(&mut self, _pc: usize, _instruction: u8) -> bool { true }
 
 	fn trace_prepare_execute(&mut self, pc: usize, instruction: u8, gas_cost: U256) {

ethcore/src/trace/mod.rs

@@ -48,6 +48,9 @@ use header::BlockNumber;
 
 /// This trait is used by executive to build traces.
 pub trait Tracer: Send {
+	/// Data returned when draining the Tracer.
+	type Output;
+
 	/// Prepares call trace for given params. Noop tracer should return None.
 	fn prepare_trace_call(&self, params: &ActionParams) -> Option<Call>;
 
@@ -63,7 +66,7 @@ pub trait Tracer: Send {
 		call: Option<Call>,
 		gas_used: U256,
 		output: Option<Bytes>,
-		subs: Vec<FlatTrace>,
+		subs: Vec<Self::Output>,
 	);
 
 	/// Stores trace create info.
@@ -73,14 +76,14 @@ pub trait Tracer: Send {
 		gas_used: U256,
 		code: Option<Bytes>,
 		address: Address,
-		subs: Vec<FlatTrace>
+		subs: Vec<Self::Output>
 	);
 
 	/// Stores failed call trace.
-	fn trace_failed_call(&mut self, call: Option<Call>, subs: Vec<FlatTrace>, error: TraceError);
+	fn trace_failed_call(&mut self, call: Option<Call>, subs: Vec<Self::Output>, error: TraceError);
 
 	/// Stores failed create trace.
-	fn trace_failed_create(&mut self, create: Option<Create>, subs: Vec<FlatTrace>, error: TraceError);
+	fn trace_failed_create(&mut self, create: Option<Create>, subs: Vec<Self::Output>, error: TraceError);
 
 	/// Stores suicide info.
 	fn trace_suicide(&mut self, address: Address, balance: U256, refund_address: Address);
@@ -92,12 +95,15 @@ pub trait Tracer: Send {
 	fn subtracer(&self) -> Self where Self: Sized;
 
 	/// Consumes self and returns all traces.
-	fn drain(self) -> Vec<FlatTrace>;
+	fn drain(self) -> Vec<Self::Output>;
 }
 
 /// Used by executive to build VM traces.
 pub trait VMTracer: Send {
 
+	/// Data returned when draining the VMTracer.
+	type Output;
+
 	/// Trace the progression of interpreter to next instruction.
 	/// If tracer returns `false` it won't be called again.
 	/// @returns true if `trace_prepare_execute` and `trace_executed` should be called.
@@ -116,7 +122,7 @@ pub trait VMTracer: Send {
 	fn done_subtrace(&mut self, sub: Self) where Self: Sized;
 
 	/// Consumes self and returns the VM trace.
-	fn drain(self) -> Option<VMTrace>;
+	fn drain(self) -> Option<Self::Output>;
 }
 
 /// `DbExtras` provides an interface to query extra data which is not stored in tracesdb,

ethcore/src/trace/noop_tracer.rs

@@ -27,6 +27,8 @@ use trace::trace::{Call, Create, VMTrace, RewardType};
 pub struct NoopTracer;
 
 impl Tracer for NoopTracer {
+	type Output = FlatTrace;
+
 	fn prepare_trace_call(&self, _: &ActionParams) -> Option<Call> {
 		None
 	}
@@ -76,6 +78,8 @@ impl Tracer for NoopTracer {
 pub struct NoopVMTracer;
 
 impl VMTracer for NoopVMTracer {
+	type Output = VMTrace;
+
 	fn trace_next_instruction(&mut self, _pc: usize, _instruction: u8) -> bool { false }
 
 	fn trace_prepare_execute(&mut self, _pc: usize, _instruction: u8, _gas_cost: U256) {}