The error message gives you a reason - there is no single underlying type.
This works:
type B []byte
func Bar[T []byte|B](s T) {
for range s {}
}
But yes, your example arguably should be made to work eventually. I would
suggest filing an issue about that.
On Fri, Nov 12, 2021 at 4:47 PM tapi...@gmail.com <tapir....@gmail.com>
wrote:
> This one doesn't compile either.
> So the range operation doesn't support values of parameter types?
>
> type MyByte byte
>
> func Bar[T []byte|[]MyByte](s T) {
> for range s {} // cannot range over s (variable of type T constrained
> by []byte|[]MyByte) (type set has no single underlying
> }
>
> On Friday, November 12, 2021 at 11:40:53 PM UTC+8
> axel.wa...@googlemail.com wrote:
>
>> On Fri, Nov 12, 2021 at 4:29 PM tapi...@gmail.com <tapi...@gmail.com>
>> wrote:
>>
>>> On Friday, November 12, 2021 at 11:10:17 PM UTC+8
>>> axel.wa...@googlemail.com wrote:
>>>
>>>> `range s` works differently for string and []byte. In the former case
>>>> it iterates over utf8-encoded unicode codepoints, in the latter it iterates
>>>> over bytes.
>>>>
>>>
>>> It is true, but why it matters here?
>>>
>>
>> Because it makes `range` different operations for the purposes of
>> determining the allowed operations on a type-parameter.
>>
>>
>>>
>>>
>>>>
>>>> On Fri, Nov 12, 2021 at 3:18 PM tapi...@gmail.com <tapi...@gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>> func Bar[T []byte|string](s T) bool {
>>>>> for _, v := range s { // cannot range over s (variable of type T
>>>>> constrained by []byte|string) (T has no structural type)
>>>>> if v > 100 {
>>>>> return true
>>>>> }
>>>>> }
>>>>> return false
>>>>> }
>>>>>
>>>>> The message is quite confusing.
>>>>>
>>>>> --
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>>>>> .
>>>>>
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>>>
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