if okfor[op][t.Kind()] {
			return t
		}
	}
	return nil
}

// ConvertVal converts v into a representation appropriate for t. If
// no such representation exists, it returns constant.MakeUnknown()
// instead.
//
// If explicit is true, then conversions from integer to string are
// also allowed.
func ConvertVal(v constant.Value, t *types.Type, explicit bool) constant.Value {
	switch ct := v.Kind(); ct {