trie: prefer nil slices over zero-length slices (#19084)

trie/database.go

@@ -809,7 +809,7 @@ func (db *Database) verifyIntegrity() {
 		db.accumulate(child, reachable)
 	}
 	// Find any unreachable but cached nodes
-	unreachable := []string{}
+	var unreachable []string
 	for hash, node := range db.dirties {
 		if _, ok := reachable[hash]; !ok {
 			unreachable = append(unreachable, fmt.Sprintf("%x: {Node: %v, Parents: %d, Prev: %x, Next: %x}",

trie/proof.go

@@ -37,7 +37,7 @@ import (
 func (t *Trie) Prove(key []byte, fromLevel uint, proofDb ethdb.Putter) error {
 	// Collect all nodes on the path to key.
 	key = keybytesToHex(key)
-	nodes := []node{}
+	var nodes []node
 	tn := t.root
 	for len(key) > 0 && tn != nil {
 		switch n := tn.(type) {

trie/sync.go

@@ -157,7 +157,7 @@ func (s *Sync) AddRawEntry(hash common.Hash, depth int, parent common.Hash) {
 
 // Missing retrieves the known missing nodes from the trie for retrieval.
 func (s *Sync) Missing(max int) []common.Hash {
-	requests := []common.Hash{}
+	var requests []common.Hash
 	for !s.queue.Empty() && (max == 0 || len(requests) < max) {
 		requests = append(requests, s.queue.PopItem().(common.Hash))
 	}
@@ -254,7 +254,7 @@ func (s *Sync) children(req *request, object node) ([]*request, error) {
 		node  node
 		depth int
 	}
-	children := []child{}
+	var children []child
 
 	switch node := (object).(type) {
 	case *shortNode:

trie/sync_test.go

@@ -313,7 +313,7 @@ func TestIncompleteSync(t *testing.T) {
 	triedb := NewDatabase(diskdb)
 	sched := NewSync(srcTrie.Hash(), diskdb, nil)
 
-	added := []common.Hash{}
+	var added []common.Hash
 	queue := append([]common.Hash{}, sched.Missing(1)...)
 	for len(queue) > 0 {
 		// Fetch a batch of trie nodes