Reduce "shim types", introduce agreement.Block

agreement.Block is similar to what was agreement.ProposableBlock, but
rather than being an interface it is a concrete type.  Therefore,
there can be no confusion: A validated block is not an agreement.Block
just because it has a Block() method.

Instead, FinalizeBlock methods explicit copy their internal Block()
objects into agreement.Block objects during finalization.

This PR also eliminates node.validatedBlock as
*ledgercore.ValidatedBlock implements agreement.ValidatedBlock
already, no wrapper is needed.  Blocks remain as immutable as before.

agreement/abstractions.go

@@ -84,23 +84,20 @@ type BlockFactory interface {
 // An UnfinishedBlock represents a Block produced by a BlockFactory
 // and must be finalized before being proposed by agreement.
 type UnfinishedBlock interface {
-	// WithSeed creates a copy of this UnfinishedBlock with its
-	// cryptographically random seed set to the given value.
+	// FinishBlock creates a Proposaable block, having set the cryptographically
+	// random seed and payout related fields.
 	//
 	// Calls to Seed() or to Digest() on the copy's Block must
 	// reflect the value of the new seed.
-	FinishBlock(seed committee.Seed, proposer basics.Address, eligible bool) ProposableBlock
+	FinishBlock(seed committee.Seed, proposer basics.Address, eligible bool) Block
 
 	Round() basics.Round
 }
 
-// An ProposableBlock represents a Block produced by a BlockFactory,
-// that was later finalized by providing the seed and the proposer,
-// and can now be proposed by agreement.
-type ProposableBlock interface {
-	// Block returns the underlying block that has been assembled.
-	Block() bookkeeping.Block
-}
+// A Block (in agreement) represents an UnfinishedBlock produced by a
+// BlockFactory, that was later finalized by providing the seed and the
+// proposer, and can now be proposed by agreement.
+type Block bookkeeping.Block
 
 // A Ledger represents the sequence of Entries agreed upon by the protocol.
 // The Ledger consists of two parts: a LedgerReader and a LedgerWriter, which

agreement/agreementtest/simulate_test.go

@@ -83,13 +83,13 @@ func (b testValidatedBlock) Round() basics.Round {
 	return b.Inside.Round()
 }
 
-func (b testValidatedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) agreement.ProposableBlock {
+func (b testValidatedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) agreement.Block {
 	b.Inside.BlockHeader.Seed = s
 	b.Inside.BlockHeader.Proposer = proposer
 	if !eligible {
 		b.Inside.BlockHeader.ProposerPayout = basics.MicroAlgos{}
 	}
-	return b
+	return agreement.Block(b.Inside)
 }
 
 type testBlockValidator struct{}

agreement/common_test.go

@@ -169,13 +169,13 @@ func (b testValidatedBlock) Round() basics.Round {
 	return b.Inside.Round()
 }
 
-func (b testValidatedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) ProposableBlock {
+func (b testValidatedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) Block {
 	b.Inside.BlockHeader.Seed = s
 	b.Inside.BlockHeader.Proposer = proposer
 	if !eligible {
 		b.Inside.BlockHeader.ProposerPayout = basics.MicroAlgos{}
 	}
-	return b
+	return Block(b.Inside)
 }
 
 type testBlockValidator struct{}
@@ -538,7 +538,7 @@ func (v *voteMakerHelper) MakeRandomProposalPayload(t *testing.T, r round) (*pro
 	pb := ub.FinishBlock(committee.Seed{}, basics.Address{}, false)
 
 	var payload unauthenticatedProposal
-	payload.Block = pb.Block()
+	payload.Block = bookkeeping.Block(pb)
 	payload.SeedProof = randomVRFProof()
 
 	propVal := proposalValue{

agreement/fuzzer/ledger_test.go

@@ -97,13 +97,13 @@ func (b testValidatedBlock) Round() basics.Round {
 	return b.Inside.Round()
 }
 
-func (b testValidatedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) agreement.ProposableBlock {
+func (b testValidatedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) agreement.Block {
 	b.Inside.BlockHeader.Seed = s
 	b.Inside.BlockHeader.Proposer = proposer
 	if !eligible {
 		b.Inside.BlockHeader.ProposerPayout = basics.MicroAlgos{}
 	}
-	return b
+	return agreement.Block(b.Inside)
 }
 
 type testBlockValidator struct{}

agreement/player_permutation_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/algorand/go-algorand/config"
 	"github.com/algorand/go-algorand/crypto"
 	"github.com/algorand/go-algorand/data/basics"
+	"github.com/algorand/go-algorand/data/bookkeeping"
 	"github.com/algorand/go-algorand/data/committee"
 	"github.com/algorand/go-algorand/protocol"
 	"github.com/algorand/go-algorand/test/partitiontest"
@@ -36,7 +37,7 @@ func makeRandomProposalPayload(r round) *proposal {
 	pb := ub.FinishBlock(committee.Seed{}, basics.Address{}, false)
 
 	var payload unauthenticatedProposal
-	payload.Block = pb.Block()
+	payload.Block = bookkeeping.Block(pb)
 	payload.SeedProof = crypto.VRFProof{}
 
 	return &proposal{unauthenticatedProposal: payload}

agreement/proposal.go

@@ -102,8 +102,8 @@ type proposal struct {
 	validatedAt time.Duration
 }
 
-func makeProposalFromProposableBlock(blk ProposableBlock, pf crypto.VrfProof, origPer period, origProp basics.Address) proposal {
-	e := blk.Block()
+func makeProposalFromProposableBlock(blk Block, pf crypto.VrfProof, origPer period, origProp basics.Address) proposal {
+	e := bookkeeping.Block(blk)
 	var payload unauthenticatedProposal
 	payload.Block = e
 	payload.SeedProof = pf

node/impls.go

@@ -26,6 +26,7 @@ import (
 	"github.com/algorand/go-algorand/data/basics"
 	"github.com/algorand/go-algorand/data/bookkeeping"
 	"github.com/algorand/go-algorand/ledger"
+	"github.com/algorand/go-algorand/ledger/ledgercore"
 	"github.com/algorand/go-algorand/logging"
 	"github.com/algorand/go-algorand/network"
 	"github.com/algorand/go-algorand/util/execpool"
@@ -59,7 +60,7 @@ func (i blockValidatorImpl) Validate(ctx context.Context, e bookkeeping.Block) (
 		return nil, err
 	}
 
-	return validatedBlock{vb: lvb}, nil
+	return lvb, nil
 }
 
 // agreementLedger implements the agreement.Ledger interface.
@@ -86,7 +87,7 @@ func (l agreementLedger) EnsureBlock(e bookkeeping.Block, c agreement.Certificat
 
 // EnsureValidatedBlock implements agreement.LedgerWriter.EnsureValidatedBlock.
 func (l agreementLedger) EnsureValidatedBlock(ve agreement.ValidatedBlock, c agreement.Certificate) {
-	l.Ledger.EnsureValidatedBlock(ve.(validatedBlock).vb, c)
+	l.Ledger.EnsureValidatedBlock(ve.(*ledgercore.ValidatedBlock), c)
 	// let the network know that we've made some progress.
 	l.n.OnNetworkAdvance()
 }

node/node.go

@@ -1289,33 +1289,17 @@ func (node *AlgorandFullNode) SetCatchpointCatchupMode(catchpointCatchupMode boo
 
 }
 
-// validatedBlock satisfies agreement.ValidatedBlock
-type validatedBlock struct {
-	vb *ledgercore.ValidatedBlock
-}
-
 // unfinishedBlock satisfies agreement.UnfinishedBlock
 type unfinishedBlock struct {
 	blk *ledgercore.UnfinishedBlock
 }
 
-// proposableBlock satisfies agreement.ProposableBlock
-type proposableBlock struct {
-	blk bookkeeping.Block
-}
-
-// Block satisfies the agreement.ValidatedBlock interface.
-func (vb validatedBlock) Block() bookkeeping.Block { return vb.vb.Block() }
-
 // Round satisfies the agreement.UnfinishedBlock interface.
 func (ub unfinishedBlock) Round() basics.Round { return ub.blk.Round() }
 
-// Block satisfies the agreement.ProposableBlock interface.
-func (ab proposableBlock) Block() bookkeeping.Block { return ab.blk }
-
 // FinishBlock satisfies the agreement.UnfinishedBlock interface.
-func (ub unfinishedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) agreement.ProposableBlock {
-	return proposableBlock{blk: ub.blk.FinishBlock(s, proposer, eligible)}
+func (ub unfinishedBlock) FinishBlock(s committee.Seed, proposer basics.Address, eligible bool) agreement.Block {
+	return agreement.Block(ub.blk.FinishBlock(s, proposer, eligible))
 }
 
 // AssembleBlock implements Ledger.AssembleBlock.