Additional scan performance improvements

Move typeStack to ScanContext, so it is shared between rows.Scan calls.
Use string.Builder for string concatenations.
Simplify value assign logic.
Move convert value to the last assign step (needs for type conversions are rare).

tests/mysql/select_test.go

@@ -206,7 +206,7 @@ GROUP BY payment.customer_id;
 	"RentalID": null,
 	"Amount": 0,
 	"PaymentDate": "0001-01-01T00:00:00Z",
-	"LastUpdate": "0001-01-01T00:00:00Z",
+	"LastUpdate": null,
 	"Count": 8,
 	"Sum": 38.92,
 	"Avg": 4.865,
@@ -964,14 +964,14 @@ func TestRowsScan(t *testing.T) {
 	rows, err := stmt.Rows(context.Background(), db)
 	require.NoError(t, err)
 
+	var inventory struct {
+		model.Inventory
+
+		Film  model.Film
+		Store model.Store
+	}
+
 	for rows.Next() {
-		var inventory struct {
-			model.Inventory
-
-			Film  model.Film
-			Store model.Store
-		}
-
 		err = rows.Scan(&inventory)
 		require.NoError(t, err)
 
@@ -1056,3 +1056,50 @@ func TestScanNumericToNumber(t *testing.T) {
 	require.Equal(t, number.Float32, float32(1.234568e+09))
 	require.Equal(t, number.Float64, float64(1.23456789e+09))
 }
+
+// scan into custom base types should be equivalent to the scan into base go types
+func TestScanIntoCustomBaseTypes(t *testing.T) {
+
+	type MyUint8 uint8
+	type MyUint16 uint16
+	type MyUint32 uint32
+	type MyInt16 int16
+	type MyFloat32 float32
+	type MyFloat64 float64
+	type MyString string
+	type MyTime = time.Time
+
+	type film struct {
+		FilmID             MyUint16 `sql:"primary_key"`
+		Title              MyString
+		Description        *MyString
+		ReleaseYear        *MyInt16
+		LanguageID         MyUint8
+		OriginalLanguageID *MyUint8
+		RentalDuration     MyUint8
+		RentalRate         MyFloat32
+		Length             *MyUint32
+		ReplacementCost    MyFloat64
+		Rating             *model.FilmRating
+		SpecialFeatures    *MyString
+		LastUpdate         MyTime
+	}
+
+	stmt := SELECT(
+		Film.AllColumns,
+	).FROM(
+		Film,
+	).ORDER_BY(
+		Film.FilmID.ASC(),
+	).LIMIT(3)
+
+	var films []model.Film
+	err := stmt.Query(db, &films)
+	require.NoError(t, err)
+
+	var myFilms []film
+	err = stmt.Query(db, &myFilms)
+	require.NoError(t, err)
+
+	require.Equal(t, testutils.ToJSON(films), testutils.ToJSON(myFilms))
+}