Parachains-runtime (#1505)

* Initial commit

* v0 to v1 primitives and remove attestations

* Review fixes

* implement candidate_events

* remove dead code

polkadot/runtime/parachains/src/runtime_api_impl/v1.rs

@@ -17,6 +17,7 @@
 //! Runtimes implementing the v1 runtime API are recommended to forward directly to these
 //! functions.
 
+use sp_std::prelude::*;
 use primitives::v1::{
 	ValidatorId, ValidatorIndex, GroupRotationInfo, CoreState, GlobalValidationData,
 	Id as ParaId, OccupiedCoreAssumption, LocalValidationData, SessionIndex, ValidationCode,
@@ -239,9 +240,11 @@ pub fn candidate_pending_availability<T: initializer::Trait>(para_id: ParaId)
 /// Implementation for the `candidate_events` function of the runtime API.
 // NOTE: this runs without block initialization, as it accesses events.
 // this means it can run in a different session than other runtime APIs at the same block.
-pub fn candidate_events<T: initializer::Trait>(
-	extract_event: impl Fn(<T as system::Trait>::Event) -> Option<inclusion::Event<T>>,
-) -> Vec<CandidateEvent<T::Hash>> {
+pub fn candidate_events<T, F>(extract_event: F) -> Vec<CandidateEvent<T::Hash>>
+where
+	T: initializer::Trait,
+	F: Fn(<T as system::Trait>::Event) -> Option<inclusion::Event<T>>,
+{
 	use inclusion::Event as RawEvent;
 
 	<system::Module<T>>::events().into_iter()