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

2 files changed, 6 insertions, 8 deletions

diff --git a/ethdb/database_test.go b/ethdb/database_test.go
index 5e4a3ca34..2deb50988 100644
--- a/ethdb/database_test.go
+++ b/ethdb/database_test.go
@@ -53,8 +53,7 @@ func TestLDB_PutGet(t *testing.T) {
 }
 
 func TestMemoryDB_PutGet(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-	testPutGet(db, t)
+	testPutGet(ethdb.NewMemDatabase(), t)
 }
 
 func testPutGet(db ethdb.Database, t *testing.T) {
@@ -131,8 +130,7 @@ func TestLDB_ParallelPutGet(t *testing.T) {
 }
 
 func TestMemoryDB_ParallelPutGet(t *testing.T) {
-	db, _ := ethdb.NewMemDatabase()
-	testParallelPutGet(db, t)
+	testParallelPutGet(ethdb.NewMemDatabase(), t)
 }
 
 func testParallelPutGet(db ethdb.Database, t *testing.T) {
diff --git a/ethdb/memory_database.go b/ethdb/memory_database.go
index 8efd7bf84..c57042920 100644
--- a/ethdb/memory_database.go
+++ b/ethdb/memory_database.go
@@ -31,16 +31,16 @@ type MemDatabase struct {
 	lock sync.RWMutex
 }
 
-func NewMemDatabase() (*MemDatabase, error) {
+func NewMemDatabase() *MemDatabase {
 	return &MemDatabase{
 		db: make(map[string][]byte),
-	}, nil
+	}
 }
 
-func NewMemDatabaseWithCap(size int) (*MemDatabase, error) {
+func NewMemDatabaseWithCap(size int) *MemDatabase {
 	return &MemDatabase{
 		db: make(map[string][]byte, size),
-	}, nil
+	}
 }
 
 func (db *MemDatabase) Put(key []byte, value []byte) error {