fix: correct ArrayOf implementation

* Add compile-time assertions
* Add test for Array(String)
* Fix DecodeColumn, RowAppend

proto/col_arr_go118.go → proto/col_arr_of.go

@@ -1,9 +1,14 @@
-//go:build go1.18
-
 package proto
 
 import "github.com/go-faster/errors"
 
+// Compile-time assertions for ArrayOf.
+var (
+	_ ColInput  = ArrayOf[string]((*ColStr)(nil))
+	_ ColResult = ArrayOf[string]((*ColStr)(nil))
+	_ Column    = ArrayOf[string]((*ColStr)(nil))
+)
+
 // ColumnOf is generic Column(T) constraint.
 type ColumnOf[T any] interface {
 	Column
@@ -42,7 +47,7 @@ func (c ColArrOf[T]) RowAppend(i int, target []T) []T {
 		start = int(c.Offsets[i-1])
 	}
 	for idx := start; idx < end; idx++ {
-		target = append(target, c.Data.Row(i))
+		target = append(target, c.Data.Row(idx))
 	}
 
 	return target
@@ -52,7 +57,7 @@ func (c ColArrOf[T]) Row(i int) []T {
 	return c.RowAppend(i, nil)
 }
 
-func (c ColArrOf[T]) DecodeColumn(r *Reader, rows int) error {
+func (c *ColArrOf[T]) DecodeColumn(r *Reader, rows int) error {
 	if err := c.Offsets.DecodeColumn(r, rows); err != nil {
 		return errors.Wrap(err, "read offsets")
 	}

proto/col_arr_go118_test.go → proto/col_arr_of_test.go

@@ -1,5 +1,3 @@
-//go:build go1.18
-
 package proto
 
 import "testing"

query_test.go

@@ -649,6 +649,22 @@ func TestClient_Query(t *testing.T) {
 		require.NoError(t, Conn(t).Do(ctx, selectArr))
 		require.Equal(t, proto.ColUInt8{1, 2, 3, 4}, data)
 	})
+	t.Run("SelectArrayOf", func(t *testing.T) {
+		t.Parallel()
+		arr := proto.ArrayOf[string](new(proto.ColStr))
+		selectArr := Query{
+			Body: "SELECT ['foo', 'bar', 'baz']::Array(String) as v",
+			Result: proto.Results{
+				{
+					Name: "v",
+					Data: arr,
+				},
+			},
+		}
+		require.NoError(t, Conn(t).Do(ctx, selectArr))
+		require.Equal(t, 1, arr.Rows())
+		require.Equal(t, []string{"foo", "bar", "baz"}, arr.Row(0))
+	})
 	t.Run("SelectRand", func(t *testing.T) {
 		t.Parallel()
 		const numbers = 15_249_611