Value() int
}

// A CodeVal distinguishes among go/constant.Value encodings.
type CodeVal int

func (c CodeVal) Marker() SyncMarker { return SyncVal }
func (c CodeVal) Value() int         { return int(c) }

// Note: These values are public and cannot be changed without
// updating the go/types importers.

const (
	ValBool CodeVal = iota
	ValString
	ValInt64
	ValBigInt
	ValBigRat

	val := r.scalar()
	if isComplex {
		val = constant.BinaryOp(val, token.ADD, constant.MakeImag(r.scalar()))
	}
	return val
}

func (r *Decoder) scalar() constant.Value {
	switch tag := CodeVal(r.Code(SyncVal)); tag {
	default:
		panic(fmt.Errorf("unexpected scalar tag: %v", tag))

	case ValBool:
		return constant.MakeBool(r.Bool())
	case ValString:
		return constant.MakeString(r.String())