all: get rid of error when creating memory database (#16716)

* all: get rid of error when create mdb

* core: clean up variables definition

* all: inline mdb definition

19 files changed, 96 insertions, 131 deletions

diff --git a/core/bench_test.go b/core/bench_test.go
index ee30cfed0..748aebe40 100644
--- a/core/bench_test.go
+++ b/core/bench_test.go
@@ -149,7 +149,7 @@ func benchInsertChain(b *testing.B, disk bool, gen func(int, *BlockGen)) {
 	// Create the database in memory or in a temporary directory.
 	var db ethdb.Database
 	if !disk {
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 	} else {
 		dir, err := ioutil.TempDir("", "eth-core-bench")
 		if err != nil {
diff --git a/core/block_validator_test.go b/core/block_validator_test.go
index e334b3c3c..2a171218e 100644
--- a/core/block_validator_test.go
+++ b/core/block_validator_test.go
@@ -32,7 +32,7 @@ import (
 func TestHeaderVerification(t *testing.T) {
 	// Create a simple chain to verify
 	var (
-		testdb, _ = ethdb.NewMemDatabase()
+		testdb    = ethdb.NewMemDatabase()
 		gspec     = &Genesis{Config: params.TestChainConfig}
 		genesis   = gspec.MustCommit(testdb)
 		blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 8, nil)
@@ -84,7 +84,7 @@ func TestHeaderConcurrentVerification32(t *testing.T) { testHeaderConcurrentVeri
 func testHeaderConcurrentVerification(t *testing.T, threads int) {
 	// Create a simple chain to verify
 	var (
-		testdb, _ = ethdb.NewMemDatabase()
+		testdb    = ethdb.NewMemDatabase()
 		gspec     = &Genesis{Config: params.TestChainConfig}
 		genesis   = gspec.MustCommit(testdb)
 		blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 8, nil)
@@ -156,7 +156,7 @@ func TestHeaderConcurrentAbortion32(t *testing.T) { testHeaderConcurrentAbortion
 func testHeaderConcurrentAbortion(t *testing.T, threads int) {
 	// Create a simple chain to verify
 	var (
-		testdb, _ = ethdb.NewMemDatabase()
+		testdb    = ethdb.NewMemDatabase()
 		gspec     = &Genesis{Config: params.TestChainConfig}
 		genesis   = gspec.MustCommit(testdb)
 		blocks, _ = GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), testdb, 1024, nil)
diff --git a/core/blockchain_test.go b/core/blockchain_test.go
index c1638c31f..89c071174 100644
--- a/core/blockchain_test.go
+++ b/core/blockchain_test.go
@@ -569,11 +569,11 @@ func testInsertNonceError(t *testing.T, full bool) {
 func TestFastVsFullChains(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		gendb, _ = ethdb.NewMemDatabase()
-		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-		address  = crypto.PubkeyToAddress(key.PublicKey)
-		funds    = big.NewInt(1000000000)
-		gspec    = &Genesis{
+		gendb   = ethdb.NewMemDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000)
+		gspec   = &Genesis{
 			Config: params.TestChainConfig,
 			Alloc:  GenesisAlloc{address: {Balance: funds}},
 		}
@@ -599,7 +599,7 @@ func TestFastVsFullChains(t *testing.T) {
 		}
 	})
 	// Import the chain as an archive node for the comparison baseline
-	archiveDb, _ := ethdb.NewMemDatabase()
+	archiveDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
 	archive, _ := NewBlockChain(archiveDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
 	defer archive.Stop()
@@ -608,7 +608,7 @@ func TestFastVsFullChains(t *testing.T) {
 		t.Fatalf("failed to process block %d: %v", n, err)
 	}
 	// Fast import the chain as a non-archive node to test
-	fastDb, _ := ethdb.NewMemDatabase()
+	fastDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
 	fast, _ := NewBlockChain(fastDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
 	defer fast.Stop()
@@ -657,12 +657,12 @@ func TestFastVsFullChains(t *testing.T) {
 func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		gendb, _ = ethdb.NewMemDatabase()
-		key, _   = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
-		address  = crypto.PubkeyToAddress(key.PublicKey)
-		funds    = big.NewInt(1000000000)
-		gspec    = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{address: {Balance: funds}}}
-		genesis  = gspec.MustCommit(gendb)
+		gendb   = ethdb.NewMemDatabase()
+		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
+		address = crypto.PubkeyToAddress(key.PublicKey)
+		funds   = big.NewInt(1000000000)
+		gspec   = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{address: {Balance: funds}}}
+		genesis = gspec.MustCommit(gendb)
 	)
 	height := uint64(1024)
 	blocks, receipts := GenerateChain(gspec.Config, genesis, ethash.NewFaker(), gendb, int(height), nil)
@@ -685,7 +685,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 		}
 	}
 	// Import the chain as an archive node and ensure all pointers are updated
-	archiveDb, _ := ethdb.NewMemDatabase()
+	archiveDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(archiveDb)
 
 	archive, _ := NewBlockChain(archiveDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
@@ -699,7 +699,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	assert(t, "archive", archive, height/2, height/2, height/2)
 
 	// Import the chain as a non-archive node and ensure all pointers are updated
-	fastDb, _ := ethdb.NewMemDatabase()
+	fastDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(fastDb)
 	fast, _ := NewBlockChain(fastDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
 	defer fast.Stop()
@@ -719,7 +719,7 @@ func TestLightVsFastVsFullChainHeads(t *testing.T) {
 	assert(t, "fast", fast, height/2, height/2, 0)
 
 	// Import the chain as a light node and ensure all pointers are updated
-	lightDb, _ := ethdb.NewMemDatabase()
+	lightDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(lightDb)
 
 	light, _ := NewBlockChain(lightDb, nil, gspec.Config, ethash.NewFaker(), vm.Config{})
@@ -742,7 +742,7 @@ func TestChainTxReorgs(t *testing.T) {
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
 		addr2   = crypto.PubkeyToAddress(key2.PublicKey)
 		addr3   = crypto.PubkeyToAddress(key3.PublicKey)
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		gspec   = &Genesis{
 			Config:   params.TestChainConfig,
 			GasLimit: 3141592,
@@ -854,7 +854,7 @@ func TestLogReorgs(t *testing.T) {
 	var (
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		// this code generates a log
 		code    = common.Hex2Bytes("60606040525b7f24ec1d3ff24c2f6ff210738839dbc339cd45a5294d85c79361016243157aae7b60405180905060405180910390a15b600a8060416000396000f360606040526008565b00")
 		gspec   = &Genesis{Config: params.TestChainConfig, Alloc: GenesisAlloc{addr1: {Balance: big.NewInt(10000000000000)}}}
@@ -898,7 +898,7 @@ func TestLogReorgs(t *testing.T) {
 
 func TestReorgSideEvent(t *testing.T) {
 	var (
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		key1, _ = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
 		gspec   = &Genesis{
@@ -1026,7 +1026,7 @@ func TestCanonicalBlockRetrieval(t *testing.T) {
 func TestEIP155Transition(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		db, _      = ethdb.NewMemDatabase()
+		db         = ethdb.NewMemDatabase()
 		key, _     = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		address    = crypto.PubkeyToAddress(key.PublicKey)
 		funds      = big.NewInt(1000000000)
@@ -1130,7 +1130,7 @@ func TestEIP155Transition(t *testing.T) {
 func TestEIP161AccountRemoval(t *testing.T) {
 	// Configure and generate a sample block chain
 	var (
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 		key, _  = crypto.HexToECDSA("b71c71a67e1177ad4e901695e1b4b9ee17ae16c6668d313eac2f96dbcda3f291")
 		address = crypto.PubkeyToAddress(key.PublicKey)
 		funds   = big.NewInt(1000000000)
@@ -1202,7 +1202,7 @@ func TestBlockchainHeaderchainReorgConsistency(t *testing.T) {
 	// Generate a canonical chain to act as the main dataset
 	engine := ethash.NewFaker()
 
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)
 	blocks, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 64, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{1}) })
 
@@ -1218,7 +1218,7 @@ func TestBlockchainHeaderchainReorgConsistency(t *testing.T) {
 	}
 	// Import the canonical and fork chain side by side, verifying the current block
 	// and current header consistency
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	new(Genesis).MustCommit(diskdb)
 
 	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
@@ -1247,7 +1247,7 @@ func TestTrieForkGC(t *testing.T) {
 	// Generate a canonical chain to act as the main dataset
 	engine := ethash.NewFaker()
 
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)
 	blocks, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 2*triesInMemory, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{1}) })
 
@@ -1262,7 +1262,7 @@ func TestTrieForkGC(t *testing.T) {
 		forks[i] = fork[0]
 	}
 	// Import the canonical and fork chain side by side, forcing the trie cache to cache both
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	new(Genesis).MustCommit(diskdb)
 
 	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
@@ -1293,7 +1293,7 @@ func TestLargeReorgTrieGC(t *testing.T) {
 	// Generate the original common chain segment and the two competing forks
 	engine := ethash.NewFaker()
 
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := new(Genesis).MustCommit(db)
 
 	shared, _ := GenerateChain(params.TestChainConfig, genesis, engine, db, 64, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{1}) })
@@ -1301,7 +1301,7 @@ func TestLargeReorgTrieGC(t *testing.T) {
 	competitor, _ := GenerateChain(params.TestChainConfig, shared[len(shared)-1], engine, db, 2*triesInMemory+1, func(i int, b *BlockGen) { b.SetCoinbase(common.Address{3}) })
 
 	// Import the shared chain and the original canonical one
-	diskdb, _ := ethdb.NewMemDatabase()
+	diskdb := ethdb.NewMemDatabase()
 	new(Genesis).MustCommit(diskdb)
 
 	chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
@@ -1361,7 +1361,7 @@ func benchmarkLargeNumberOfValueToNonexisting(b *testing.B, numTxs, numBlocks in
 	)
 	// Generate the original common chain segment and the two competing forks
 	engine := ethash.NewFaker()
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	genesis := gspec.MustCommit(db)
 
 	blockGenerator := func(i int, block *BlockGen) {
@@ -1383,7 +1383,7 @@ func benchmarkLargeNumberOfValueToNonexisting(b *testing.B, numTxs, numBlocks in
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		// Import the shared chain and the original canonical one
-		diskdb, _ := ethdb.NewMemDatabase()
+		diskdb := ethdb.NewMemDatabase()
 		gspec.MustCommit(diskdb)
 
 		chain, err := NewBlockChain(diskdb, nil, params.TestChainConfig, engine, vm.Config{})
diff --git a/core/chain_indexer_test.go b/core/chain_indexer_test.go
index 3205616e8..550caf556 100644
--- a/core/chain_indexer_test.go
+++ b/core/chain_indexer_test.go
@@ -48,7 +48,7 @@ func TestChainIndexerWithChildren(t *testing.T) {
 // multiple backends. The section size and required confirmation count parameters
 // are randomized.
 func testChainIndexer(t *testing.T, count int) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	defer db.Close()
 
 	// Create a chain of indexers and ensure they all report empty
diff --git a/core/chain_makers.go b/core/chain_makers.go
index 31c9e3fb7..fcba90bb8 100644
--- a/core/chain_makers.go
+++ b/core/chain_makers.go
@@ -256,11 +256,12 @@ func makeHeader(chain consensus.ChainReader, parent *types.Block, state *state.S
 // chain. Depending on the full flag, if creates either a full block chain or a
 // header only chain.
 func newCanonical(engine consensus.Engine, n int, full bool) (ethdb.Database, *BlockChain, error) {
-	// Initialize a fresh chain with only a genesis block
-	gspec := new(Genesis)
-	db, _ := ethdb.NewMemDatabase()
-	genesis := gspec.MustCommit(db)
+	var (
+		db      = ethdb.NewMemDatabase()
+		genesis = new(Genesis).MustCommit(db)
+	)
 
+	// Initialize a fresh chain with only a genesis block
 	blockchain, _ := NewBlockChain(db, nil, params.AllEthashProtocolChanges, engine, vm.Config{})
 	// Create and inject the requested chain
 	if n == 0 {
diff --git a/core/chain_makers_test.go b/core/chain_makers_test.go
index 93be43ddc..5015d1f48 100644
--- a/core/chain_makers_test.go
+++ b/core/chain_makers_test.go
@@ -36,7 +36,7 @@ func ExampleGenerateChain() {
 		addr1   = crypto.PubkeyToAddress(key1.PublicKey)
 		addr2   = crypto.PubkeyToAddress(key2.PublicKey)
 		addr3   = crypto.PubkeyToAddress(key3.PublicKey)
-		db, _   = ethdb.NewMemDatabase()
+		db      = ethdb.NewMemDatabase()
 	)
 
 	// Ensure that key1 has some funds in the genesis block.
diff --git a/core/dao_test.go b/core/dao_test.go
index e0a3e3ff3..284b1d98b 100644
--- a/core/dao_test.go
+++ b/core/dao_test.go
@@ -32,13 +32,13 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	forkBlock := big.NewInt(32)
 
 	// Generate a common prefix for both pro-forkers and non-forkers
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	gspec := new(Genesis)
 	genesis := gspec.MustCommit(db)
 	prefix, _ := GenerateChain(params.TestChainConfig, genesis, ethash.NewFaker(), db, int(forkBlock.Int64()-1), func(i int, gen *BlockGen) {})
 
 	// Create the concurrent, conflicting two nodes
-	proDb, _ := ethdb.NewMemDatabase()
+	proDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(proDb)
 
 	proConf := *params.TestChainConfig
@@ -48,7 +48,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	proBc, _ := NewBlockChain(proDb, nil, &proConf, ethash.NewFaker(), vm.Config{})
 	defer proBc.Stop()
 
-	conDb, _ := ethdb.NewMemDatabase()
+	conDb := ethdb.NewMemDatabase()
 	gspec.MustCommit(conDb)
 
 	conConf := *params.TestChainConfig
@@ -67,7 +67,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 	// Try to expand both pro-fork and non-fork chains iteratively with other camp's blocks
 	for i := int64(0); i < params.DAOForkExtraRange.Int64(); i++ {
 		// Create a pro-fork block, and try to feed into the no-fork chain
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
 		bc, _ := NewBlockChain(db, nil, &conConf, ethash.NewFaker(), vm.Config{})
 		defer bc.Stop()
@@ -92,7 +92,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 			t.Fatalf("contra-fork chain didn't accepted no-fork block: %v", err)
 		}
 		// Create a no-fork block, and try to feed into the pro-fork chain
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 		gspec.MustCommit(db)
 		bc, _ = NewBlockChain(db, nil, &proConf, ethash.NewFaker(), vm.Config{})
 		defer bc.Stop()
@@ -118,7 +118,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		}
 	}
 	// Verify that contra-forkers accept pro-fork extra-datas after forking finishes
-	db, _ = ethdb.NewMemDatabase()
+	db = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
 	bc, _ := NewBlockChain(db, nil, &conConf, ethash.NewFaker(), vm.Config{})
 	defer bc.Stop()
@@ -138,7 +138,7 @@ func TestDAOForkRangeExtradata(t *testing.T) {
 		t.Fatalf("contra-fork chain didn't accept pro-fork block post-fork: %v", err)
 	}
 	// Verify that pro-forkers accept contra-fork extra-datas after forking finishes
-	db, _ = ethdb.NewMemDatabase()
+	db = ethdb.NewMemDatabase()
 	gspec.MustCommit(db)
 	bc, _ = NewBlockChain(db, nil, &proConf, ethash.NewFaker(), vm.Config{})
 	defer bc.Stop()
diff --git a/core/genesis.go b/core/genesis.go
index c0a636ab2..9190e2ba2 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -222,7 +222,7 @@ func (g *Genesis) configOrDefault(ghash common.Hash) *params.ChainConfig {
 // to the given database (or discards it if nil).
 func (g *Genesis) ToBlock(db ethdb.Database) *types.Block {
 	if db == nil {
-		db, _ = ethdb.NewMemDatabase()
+		db = ethdb.NewMemDatabase()
 	}
 	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
 	for addr, account := range g.Alloc {
diff --git a/core/genesis_test.go b/core/genesis_test.go
index 613434e20..2d7f94f8f 100644
--- a/core/genesis_test.go
+++ b/core/genesis_test.go
@@ -141,7 +141,7 @@ func TestSetupGenesis(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		db, _ := ethdb.NewMemDatabase()
+		db := ethdb.NewMemDatabase()
 		config, hash, err := test.fn(db)
 		// Check the return values.
 		if !reflect.DeepEqual(err, test.wantErr) {
diff --git a/core/helper_test.go b/core/helper_test.go
index 698a2924c..051384d85 100644
--- a/core/helper_test.go
+++ b/core/helper_test.go
@@ -18,7 +18,6 @@ package core
 
 import (
 	"container/list"
-	"fmt"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -77,18 +76,11 @@ func (tm *TestManager) Db() ethdb.Database {
 }
 
 func NewTestManager() *TestManager {
-	db, err := ethdb.NewMemDatabase()
-	if err != nil {
-		fmt.Println("Could not create mem-db, failing")
-		return nil
-	}
-
 	testManager := &TestManager{}
 	testManager.eventMux = new(event.TypeMux)
-	testManager.db = db
+	testManager.db = ethdb.NewMemDatabase()
 	// testManager.txPool = NewTxPool(testManager)
 	// testManager.blockChain = NewBlockChain(testManager)
 	// testManager.stateManager = NewStateManager(testManager)
-
 	return testManager
 }
diff --git a/core/rawdb/accessors_chain_test.go b/core/rawdb/accessors_chain_test.go
index 84c9c9aeb..9ddae6e2b 100644
--- a/core/rawdb/accessors_chain_test.go
+++ b/core/rawdb/accessors_chain_test.go
@@ -30,7 +30,7 @@ import (
 
 // Tests block header storage and retrieval operations.
 func TestHeaderStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test header to move around the database and make sure it's really new
 	header := &types.Header{Number: big.NewInt(42), Extra: []byte("test header")}
@@ -63,7 +63,7 @@ func TestHeaderStorage(t *testing.T) {
 
 // Tests block body storage and retrieval operations.
 func TestBodyStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test body to move around the database and make sure it's really new
 	body := &types.Body{Uncles: []*types.Header{{Extra: []byte("test header")}}}
@@ -101,7 +101,7 @@ func TestBodyStorage(t *testing.T) {
 
 // Tests block storage and retrieval operations.
 func TestBlockStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test block to move around the database and make sure it's really new
 	block := types.NewBlockWithHeader(&types.Header{
@@ -151,7 +151,7 @@ func TestBlockStorage(t *testing.T) {
 
 // Tests that partial block contents don't get reassembled into full blocks.
 func TestPartialBlockStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	block := types.NewBlockWithHeader(&types.Header{
 		Extra:       []byte("test block"),
 		UncleHash:   types.EmptyUncleHash,
@@ -185,7 +185,7 @@ func TestPartialBlockStorage(t *testing.T) {
 
 // Tests block total difficulty storage and retrieval operations.
 func TestTdStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test TD to move around the database and make sure it's really new
 	hash, td := common.Hash{}, big.NewInt(314)
@@ -208,7 +208,7 @@ func TestTdStorage(t *testing.T) {
 
 // Tests that canonical numbers can be mapped to hashes and retrieved.
 func TestCanonicalMappingStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	// Create a test canonical number and assinged hash to move around
 	hash, number := common.Hash{0: 0xff}, uint64(314)
@@ -231,7 +231,7 @@ func TestCanonicalMappingStorage(t *testing.T) {
 
 // Tests that head headers and head blocks can be assigned, individually.
 func TestHeadStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	blockHead := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block header")})
 	blockFull := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block full")})
@@ -266,7 +266,7 @@ func TestHeadStorage(t *testing.T) {
 
 // Tests that receipts associated with a single block can be stored and retrieved.
 func TestBlockReceiptStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	receipt1 := &types.Receipt{
 		Status:            types.ReceiptStatusFailed,
diff --git a/core/rawdb/accessors_indexes_test.go b/core/rawdb/accessors_indexes_test.go
index d9c129163..d9c10e149 100644
--- a/core/rawdb/accessors_indexes_test.go
+++ b/core/rawdb/accessors_indexes_test.go
@@ -27,7 +27,7 @@ import (
 
 // Tests that positional lookup metadata can be stored and retrieved.
 func TestLookupStorage(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 
 	tx1 := types.NewTransaction(1, common.BytesToAddress([]byte{0x11}), big.NewInt(111), 1111, big.NewInt(11111), []byte{0x11, 0x11, 0x11})
 	tx2 := types.NewTransaction(2, common.BytesToAddress([]byte{0x22}), big.NewInt(222), 2222, big.NewInt(22222), []byte{0x22, 0x22, 0x22})
diff --git a/core/state/managed_state_test.go b/core/state/managed_state_test.go
index 1cfdd3a89..3d9c4e867 100644
--- a/core/state/managed_state_test.go
+++ b/core/state/managed_state_test.go
@@ -26,8 +26,7 @@ import (
 var addr = common.BytesToAddress([]byte("test"))
 
 func create() (*ManagedState, *account) {
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := New(common.Hash{}, NewDatabase(db))
+	statedb, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 	ms := ManageState(statedb)
 	ms.StateDB.SetNonce(addr, 100)
 	ms.accounts[addr] = newAccount(ms.StateDB.getStateObject(addr))
diff --git a/core/state/state_test.go b/core/state/state_test.go
index 6d42d63d8..12778f6f1 100644
--- a/core/state/state_test.go
+++ b/core/state/state_test.go
@@ -87,7 +87,7 @@ func (s *StateSuite) TestDump(c *checker.C) {
 }
 
 func (s *StateSuite) SetUpTest(c *checker.C) {
-	s.db, _ = ethdb.NewMemDatabase()
+	s.db = ethdb.NewMemDatabase()
 	s.state, _ = New(common.Hash{}, NewDatabase(s.db))
 }
 
@@ -133,8 +133,7 @@ func (s *StateSuite) TestSnapshotEmpty(c *checker.C) {
 // use testing instead of checker because checker does not support
 // printing/logging in tests (-check.vv does not work)
 func TestSnapshot2(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-	state, _ := New(common.Hash{}, NewDatabase(db))
+	state, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 
 	stateobjaddr0 := toAddr([]byte("so0"))
 	stateobjaddr1 := toAddr([]byte("so1"))
diff --git a/core/state/statedb_test.go b/core/state/statedb_test.go
index 420ca745c..e2b349de8 100644
--- a/core/state/statedb_test.go
+++ b/core/state/statedb_test.go
@@ -39,7 +39,7 @@ import (
 // actually committing the state.
 func TestUpdateLeaks(t *testing.T) {
 	// Create an empty state database
-	db, _ := ethdb.NewMemDatabase()
+	db := ethdb.NewMemDatabase()
 	state, _ := New(common.Hash{}, NewDatabase(db))
 
 	// Update it with some accounts
@@ -66,8 +66,8 @@ func TestUpdateLeaks(t *testing.T) {
 // only the one right before the commit.
 func TestIntermediateLeaks(t *testing.T) {
 	// Create two state databases, one transitioning to the final state, the other final from the beginning
-	transDb, _ := ethdb.NewMemDatabase()
-	finalDb, _ := ethdb.NewMemDatabase()
+	transDb := ethdb.NewMemDatabase()
+	finalDb := ethdb.NewMemDatabase()
 	transState, _ := New(common.Hash{}, NewDatabase(transDb))
 	finalState, _ := New(common.Hash{}, NewDatabase(finalDb))
 
@@ -122,8 +122,7 @@ func TestIntermediateLeaks(t *testing.T) {
 // https://github.com/ethereum/go-ethereum/pull/15549.
 func TestCopy(t *testing.T) {
 	// Create a random state test to copy and modify "independently"
-	db, _ := ethdb.NewMemDatabase()
-	orig, _ := New(common.Hash{}, NewDatabase(db))
+	orig, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 
 	for i := byte(0); i < 255; i++ {
 		obj := orig.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
@@ -334,8 +333,7 @@ func (test *snapshotTest) String() string {
 func (test *snapshotTest) run() bool {
 	// Run all actions and create snapshots.
 	var (
-		db, _        = ethdb.NewMemDatabase()
-		state, _     = New(common.Hash{}, NewDatabase(db))
+		state, _     = New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 		snapshotRevs = make([]int, len(test.snapshots))
 		sindex       = 0
 	)
@@ -426,8 +424,7 @@ func (s *StateSuite) TestTouchDelete(c *check.C) {
 // TestCopyOfCopy tests that modified objects are carried over to the copy, and the copy of the copy.
 // See https://github.com/ethereum/go-ethereum/pull/15225#issuecomment-380191512
 func TestCopyOfCopy(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-	sdb, _ := New(common.Hash{}, NewDatabase(db))
+	sdb, _ := New(common.Hash{}, NewDatabase(ethdb.NewMemDatabase()))
 	addr := common.HexToAddress("aaaa")
 	sdb.SetBalance(addr, big.NewInt(42))
 
diff --git a/core/state/sync_test.go b/core/state/sync_test.go
index 8f14a44e7..317740160 100644
--- a/core/state/sync_test.go
+++ b/core/state/sync_test.go
@@ -38,8 +38,7 @@ type testAccount struct {
 // makeTestState create a sample test state to test node-wise reconstruction.
 func makeTestState() (Database, common.Hash, []*testAccount) {
 	// Create an empty state
-	diskdb, _ := ethdb.NewMemDatabase()
-	db := NewDatabase(diskdb)
+	db := NewDatabase(ethdb.NewMemDatabase())
 	state, _ := New(common.Hash{}, db)
 
 	// Fill it with some arbitrary data
@@ -125,8 +124,7 @@ func checkStateConsistency(db ethdb.Database, root common.Hash) error {
 // Tests that an empty state is not scheduled for syncing.
 func TestEmptyStateSync(t *testing.T) {
 	empty := common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
-	db, _ := ethdb.NewMemDatabase()
-	if req := NewStateSync(empty, db).Missing(1); len(req) != 0 {
+	if req := NewStateSync(empty, ethdb.NewMemDatabase()).Missing(1); len(req) != 0 {
 		t.Errorf("content requested for empty state: %v", req)
 	}
 }
@@ -141,7 +139,7 @@ func testIterativeStateSync(t *testing.T, batch int) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := append([]common.Hash{}, sched.Missing(batch)...)
@@ -173,7 +171,7 @@ func TestIterativeDelayedStateSync(t *testing.T) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := append([]common.Hash{}, sched.Missing(0)...)
@@ -210,7 +208,7 @@ func testIterativeRandomStateSync(t *testing.T, batch int) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := make(map[common.Hash]struct{})
@@ -250,7 +248,7 @@ func TestIterativeRandomDelayedStateSync(t *testing.T) {
 	srcDb, srcRoot, srcAccounts := makeTestState()
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	queue := make(map[common.Hash]struct{})
@@ -297,7 +295,7 @@ func TestIncompleteStateSync(t *testing.T) {
 	checkTrieConsistency(srcDb.TrieDB().DiskDB().(ethdb.Database), srcRoot)
 
 	// Create a destination state and sync with the scheduler
-	dstDb, _ := ethdb.NewMemDatabase()
+	dstDb := ethdb.NewMemDatabase()
 	sched := NewStateSync(srcRoot, dstDb)
 
 	added := []common.Hash{}
diff --git a/core/tx_pool_test.go b/core/tx_pool_test.go
index f0f86415d..e7f52075e 100644
--- a/core/tx_pool_test.go
+++ b/core/tx_pool_test.go
@@ -78,8 +78,7 @@ func pricedTransaction(nonce uint64, gaslimit uint64, gasprice *big.Int, key *ec
 }
 
 func setupTxPool() (*TxPool, *ecdsa.PrivateKey) {
-	diskdb, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(diskdb))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	key, _ := crypto.GenerateKey()
@@ -158,8 +157,7 @@ func (c *testChain) State() (*state.StateDB, error) {
 	// a state change between those fetches.
 	stdb := c.statedb
 	if *c.trigger {
-		db, _ := ethdb.NewMemDatabase()
-		c.statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		c.statedb, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		// simulate that the new head block included tx0 and tx1
 		c.statedb.SetNonce(c.address, 2)
 		c.statedb.SetBalance(c.address, new(big.Int).SetUint64(params.Ether))
@@ -175,10 +173,9 @@ func TestStateChangeDuringTransactionPoolReset(t *testing.T) {
 	t.Parallel()
 
 	var (
-		db, _      = ethdb.NewMemDatabase()
 		key, _     = crypto.GenerateKey()
 		address    = crypto.PubkeyToAddress(key.PublicKey)
-		statedb, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		trigger    = false
 	)
 
@@ -332,8 +329,7 @@ func TestTransactionChainFork(t *testing.T) {
 
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 	resetState := func() {
-		db, _ := ethdb.NewMemDatabase()
-		statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		statedb.AddBalance(addr, big.NewInt(100000000000000))
 
 		pool.chain = &testBlockChain{statedb, 1000000, new(event.Feed)}
@@ -362,8 +358,7 @@ func TestTransactionDoubleNonce(t *testing.T) {
 
 	addr := crypto.PubkeyToAddress(key.PublicKey)
 	resetState := func() {
-		db, _ := ethdb.NewMemDatabase()
-		statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+		statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 		statedb.AddBalance(addr, big.NewInt(100000000000000))
 
 		pool.chain = &testBlockChain{statedb, 1000000, new(event.Feed)}
@@ -553,8 +548,7 @@ func TestTransactionPostponing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the postponing with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -769,8 +763,7 @@ func testTransactionQueueGlobalLimiting(t *testing.T, nolocals bool) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -858,8 +851,7 @@ func testTransactionQueueTimeLimiting(t *testing.T, nolocals bool) {
 	evictionInterval = time.Second
 
 	// Create the pool to test the non-expiration enforcement
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1013,8 +1005,7 @@ func TestTransactionPendingGlobalLimiting(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1060,8 +1051,7 @@ func TestTransactionCapClearsFromAll(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1095,8 +1085,7 @@ func TestTransactionPendingMinimumAllowance(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the limit enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1144,8 +1133,7 @@ func TestTransactionPoolRepricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -1266,8 +1254,7 @@ func TestTransactionPoolRepricingKeepsLocals(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -1329,8 +1316,7 @@ func TestTransactionPoolUnderpricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1436,8 +1422,7 @@ func TestTransactionPoolStableUnderpricing(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1503,8 +1488,7 @@ func TestTransactionReplacement(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the pricing enforcement with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
@@ -1598,8 +1582,7 @@ func testTransactionJournaling(t *testing.T, nolocals bool) {
 	os.Remove(journal)
 
 	// Create the original pool to inject transaction into the journal
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	config := testTxPoolConfig
@@ -1697,8 +1680,7 @@ func TestTransactionStatusCheck(t *testing.T) {
 	t.Parallel()
 
 	// Create the pool to test the status retrievals with
-	db, _ := ethdb.NewMemDatabase()
-	statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	statedb, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	blockchain := &testBlockChain{statedb, 1000000, new(event.Feed)}
 
 	pool := NewTxPool(testTxPoolConfig, params.TestChainConfig, blockchain)
diff --git a/core/vm/runtime/runtime.go b/core/vm/runtime/runtime.go
index 5ac546406..c8c5d34d9 100644
--- a/core/vm/runtime/runtime.go
+++ b/core/vm/runtime/runtime.go
@@ -99,8 +99,7 @@ func Execute(code, input []byte, cfg *Config) ([]byte, *state.StateDB, error) {
 	setDefaults(cfg)
 
 	if cfg.State == nil {
-		db, _ := ethdb.NewMemDatabase()
-		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	}
 	var (
 		address = common.BytesToAddress([]byte("contract"))
@@ -130,8 +129,7 @@ func Create(input []byte, cfg *Config) ([]byte, common.Address, uint64, error) {
 	setDefaults(cfg)
 
 	if cfg.State == nil {
-		db, _ := ethdb.NewMemDatabase()
-		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(db))
+		cfg.State, _ = state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	}
 	var (
 		vmenv  = NewEnv(cfg)
diff --git a/core/vm/runtime/runtime_test.go b/core/vm/runtime/runtime_test.go
index 2c4dc5026..ef664bda3 100644
--- a/core/vm/runtime/runtime_test.go
+++ b/core/vm/runtime/runtime_test.go
@@ -94,8 +94,7 @@ func TestExecute(t *testing.T) {
 }
 
 func TestCall(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-	state, _ := state.New(common.Hash{}, state.NewDatabase(db))
+	state, _ := state.New(common.Hash{}, state.NewDatabase(ethdb.NewMemDatabase()))
 	address := common.HexToAddress("0x0a")
 	state.SetCode(address, []byte{
 		byte(vm.PUSH1), 10,