block: push PrevStateRoot data into stack item, fix #2551

And add compiler/interop support for this.

pkg/compiler/analysis.go

@@ -371,7 +371,8 @@ func canConvert(s string) bool {
 		s = s[len(interopPrefix):]
 		return s != "/iterator.Iterator" && s != "/storage.Context" &&
 			s != "/native/ledger.Block" && s != "/native/ledger.Transaction" &&
-			s != "/native/management.Contract" && s != "/native/neo.AccountState"
+			s != "/native/management.Contract" && s != "/native/neo.AccountState" &&
+			s != "/native/ledger.BlockSR"
 	}
 	return true
 }

pkg/core/block/block.go

@@ -216,7 +216,7 @@ func (b *Block) GetExpectedBlockSizeWithoutTransactions(txCount int) int {
 
 // ToStackItem converts Block to stackitem.Item.
 func (b *Block) ToStackItem() stackitem.Item {
-	return stackitem.NewArray([]stackitem.Item{
+	items := []stackitem.Item{
 		stackitem.NewByteArray(b.Hash().BytesBE()),
 		stackitem.NewBigInteger(big.NewInt(int64(b.Version))),
 		stackitem.NewByteArray(b.PrevHash.BytesBE()),
@@ -226,5 +226,10 @@ func (b *Block) ToStackItem() stackitem.Item {
 		stackitem.NewBigInteger(big.NewInt(int64(b.Index))),
 		stackitem.NewByteArray(b.NextConsensus.BytesBE()),
 		stackitem.NewBigInteger(big.NewInt(int64(len(b.Transactions)))),
-	})
+	}
+	if b.StateRootEnabled {
+		items = append(items, stackitem.NewByteArray(b.PrevStateRoot.BytesBE()))
+	}
+
+	return stackitem.NewArray(items)
 }

pkg/interop/native/ledger/block.go

@@ -29,3 +29,27 @@ type Block struct {
 	// TransactionsLength represents the length of block's transactions array.
 	TransactionsLength int
 }
+
+// BlockSR is a stateroot-enabled Neo block. It's returned from the Ledger contract's
+// GetBlock method when StateRootInHeader NeoGo extension  is used. Use it only when
+// you have it enabled when you need to access PrevStateRoot field, Block is sufficient
+// otherwise. To get this data type ToBlockSR method of Block should be used. All of
+// the fields are same as in Block except PrevStateRoot.
+type BlockSR struct {
+	Hash               interop.Hash256
+	Version            int
+	PrevHash           interop.Hash256
+	MerkleRoot         interop.Hash256
+	Timestamp          int
+	Nonce              int
+	Index              int
+	NextConsensus      interop.Hash160
+	TransactionsLength int
+	// PrevStateRoot is a hash of the previous block's state root.
+	PrevStateRoot interop.Hash256
+}
+
+// ToBlockSR converts Block into BlockSR for chains with StateRootInHeader option.
+func (b *Block) ToBlockSR() *BlockSR {
+	return interface{}(b).(*BlockSR)
+}