Copy

[JustinDrake]

func (st *BeaconState) Copy() *BeaconState {
	// copy over state
	stUn := *st
	res := &stUn
	// manually copy over slices
	// validators
	copy(res.validator_registry, st.validator_registry)
	copy(res.validator_balances, st.validator_balances)
	// randao
	copy(res.latest_randao_mixes, st.latest_randao_mixes)
	// recent state
	copy(res.latest_crosslinks, st.latest_crosslinks)
	copy(res.latest_block_roots, st.latest_block_roots)
	copy(res.latest_active_index_roots, st.latest_active_index_roots)
	copy(res.latest_slashed_balances, st.latest_slashed_balances)
	copy(res.latest_attestations, st.latest_attestations)
	copy(res.batched_block_roots, st.batched_block_roots)
	// eth1
	copy(res.eth1_data_votes, st.eth1_data_votes)
	return res
}

1. Notice that (to be done with the new SSZ spec) many of these are not slices but arrays. Specifically latest_randao_mixes, latest_block_roots, latest_active_index_roots, latest_slashed_balances will all be arrays.
2. Surely there's a better way to do this :)

[protolambda]

Stumbled on a incosistency in the spec, fixed it (I think): ethereum/consensus-specs#713