From 26d4332745c00f85f30a9c6a535436f4b759cb57 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Wed, 3 Apr 2024 20:58:58 +0200
Subject: [PATCH] Use map[T]struct{} instead of map[T]bool for internal set
 types

---
 fuzz_test.go              | 26 +++++++++++---------------
 reconciler/example/ops.go | 10 +++++-----
 table.go                  |  8 ++++----
 3 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/fuzz_test.go b/fuzz_test.go
index 8e4bf60..bc02843 100644
--- a/fuzz_test.go
+++ b/fuzz_test.go
@@ -116,16 +116,16 @@ func (a *realActionLog) validate(db *statedb.DB, t *testing.T) {
 	defer a.Unlock()
 
 	// Collapse the log down to objects that are alive at the end.
-	alive := map[statedb.Table[fuzzObj]]map[uint64]bool{}
+	alive := map[statedb.Table[fuzzObj]]map[uint64]struct{}{}
 	for _, e := range a.log {
 		aliveThis, ok := alive[e.table]
 		if !ok {
-			aliveThis = map[uint64]bool{}
+			aliveThis = map[uint64]struct{}{}
 			alive[e.table] = aliveThis
 		}
 		switch e.act {
 		case actInsert:
-			aliveThis[e.id] = true
+			aliveThis[e.id] = struct{}{}
 		case actDelete:
 			delete(aliveThis, e.id)
 		case actDeleteAll:
@@ -136,31 +136,27 @@ func (a *realActionLog) validate(db *statedb.DB, t *testing.T) {
 	for table, expected := range alive {
 		txn := db.ReadTxn()
 		iter, _ := table.All(txn)
-		actual := map[uint64]bool{}
+		actual := map[uint64]struct{}{}
 		for obj, _, ok := iter.Next(); ok; obj, _, ok = iter.Next() {
-			actual[obj.id] = true
+			actual[obj.id] = struct{}{}
 		}
 		require.Equal(t, expected, actual, "validate failed, mismatching ids: %v",
 			setSymmetricDifference(actual, expected))
 	}
 }
 
-func setSymmetricDifference[T comparable, M map[T]bool](s1, s2 M) M {
+func setSymmetricDifference[T comparable, M map[T]struct{}](s1, s2 M) M {
 	counts := make(map[T]int, len(s1)+len(s2))
-	for k1, v1 := range s1 {
-		if v1 {
-			counts[k1] = 1
-		}
+	for k1 := range s1 {
+		counts[k1] = 1
 	}
-	for k2, v2 := range s2 {
-		if v2 {
-			counts[k2]++
-		}
+	for k2 := range s2 {
+		counts[k2]++
 	}
 	result := M{}
 	for k, count := range counts {
 		if count == 1 {
-			result[k] = true
+			result[k] = struct{}{}
 		}
 	}
 	return result
diff --git a/reconciler/example/ops.go b/reconciler/example/ops.go
index 3eb20e2..9f77dd2 100644
--- a/reconciler/example/ops.go
+++ b/reconciler/example/ops.go
@@ -44,19 +44,19 @@ func (ops *MemoOps) Delete(ctx context.Context, txn statedb.ReadTxn, memo *Memo)
 
 // Prune unexpected memos.
 func (ops *MemoOps) Prune(ctx context.Context, txn statedb.ReadTxn, iter statedb.Iterator[*Memo]) error {
-	expected := map[string]bool{}
+	expected := map[string]struct{}{}
 	for memo, _, ok := iter.Next(); ok; memo, _, ok = iter.Next() {
-		expected[memo.Name] = true
+		expected[memo.Name] = struct{}{}
 	}
 
 	// Find unexpected files
-	unexpected := map[string]bool{}
+	unexpected := map[string]struct{}{}
 	if entries, err := os.ReadDir(ops.directory); err != nil {
 		return err
 	} else {
 		for _, entry := range entries {
-			if !expected[entry.Name()] {
-				unexpected[entry.Name()] = true
+			if _, ok := expected[entry.Name()]; !ok {
+				unexpected[entry.Name()] = struct{}{}
 			}
 		}
 	}
diff --git a/table.go b/table.go
index 43d3cdc..8149137 100644
--- a/table.go
+++ b/table.go
@@ -71,13 +71,13 @@ func NewTable[Obj any](
 	}
 
 	// Validate that indexes have unique ids.
-	indexNames := map[string]bool{}
-	indexNames[primaryIndexer.indexName()] = true
+	indexNames := map[string]struct{}{}
+	indexNames[primaryIndexer.indexName()] = struct{}{}
 	for _, indexer := range secondaryIndexers {
-		if indexNames[indexer.indexName()] {
+		if _, ok := indexNames[indexer.indexName()]; ok {
 			return nil, tableError(tableName, fmt.Errorf("index %q: %w", indexer.indexName(), ErrDuplicateIndex))
 		}
-		indexNames[indexer.indexName()] = true
+		indexNames[indexer.indexName()] = struct{}{}
 	}
 	for name := range indexNames {
 		if strings.HasPrefix(name, reservedIndexPrefix) {