This one compiles okay:
func Bar2[T any](x T) T {
{
var T = x // T redeclared in this block
return T
}
}
So the parameter type is declared at the local top block?
On Fri, Nov 12, 2021 at 9:43 PM T L <tapir....@gmail.com> wrote:
> It is strange that my recent comments are deleted automatically if they
> are posted from the web interface.
> But now from the email interface.
>
> On Fri, Nov 12, 2021 at 9:40 PM T L <tapir....@gmail.com> wrote:
>
>> Are the followings also intended?
>>
>> func Foo[T any](T T) T { // (the 2nd) T redeclared in this block
>> return T // T (type) is not an expression
>> }
>>
>> func Bar[T any](x T) T {
>> var T = x // T redeclared in this block
>> return T
>> }
>>
>> On Fri, Nov 12, 2021 at 6:03 PM Axel Wagner <
>> axel.wagner...@googlemail.com> wrote:
>>
>>>
>>>
>>> On Fri, Nov 12, 2021 at 10:54 AM tapi...@gmail.com <tapir....@gmail.com>
>>> wrote:
>>>
>>>>
>>>>
>>>> On Friday, November 12, 2021 at 5:33:19 PM UTC+8
>>>> axel.wa...@googlemail.com wrote:
>>>>
>>>>> I suspect this issue is hard/impossible to avoid, because it must be
>>>>> possible to self- and mutually reference type-parameters, in a way that
>>>>> it's not for normal parameters, to allow to write something like
>>>>>
>>>>> type Equaler[T any] interface {
>>>>> Equal(T) bool
>>>>> }
>>>>> func Eq[T Equaler[T]](a, b T) bool {
>>>>> return a.Equal(b)
>>>>> }
>>>>>
>>>>
>>>> I don't see the same problem here. "T" and "Equaler" are two different
>>>> identifiers.
>>>>
>>>
>>> But T and T are not.
>>>
>>> The point I was making is that type-parameters must inherently be scoped
>>> in a way that makes them visible in the type-list itself, to make writing
>>> code like this possible. This isn't necessary for regular parameters and
>>> it's what makes type-parameter lists special.
>>>
>>> I *also* said that it's probably possible to devise rules which would
>>> make this possible, while allowing the example you wrote, just that those
>>> rules would have to be complicated.
>>>
>>>
>>>>
>>>>
>>>>>
>>>>> or basically any use-case for constraint-type inference.
>>>>>
>>>>> Even if we *could* allow it consistently, the rules for doing that
>>>>> would likely be pretty complex. Better to take the relatively minor hit of
>>>>> disallowing this overloading (you can always use different names for the
>>>>> type-parameters, if they conflict with the constraint you want to use)
>>>>> than
>>>>> to take the hit of complex scoping rules with lots of exceptions.
>>>>>
>>>>> On Fri, Nov 12, 2021 at 9:48 AM tapi...@gmail.com <tapi...@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> I expect the following code compilers okay, but it doesn't.
>>>>>> It looks All the three "I" in the Bar function declaration are
>>>>>> viewed as the type parameter, whereas the second one is
>>>>>> expected as the constraint I (at least by me).
>>>>>>
>>>>>> package main
>>>>>>
>>>>>> type I interface { M() }
>>>>>>
>>>>>> func Foo(i I) {
>>>>>> i.M()
>>>>>> }
>>>>>>
>>>>>> func Bar[I I](i I) { // cannot use a type parameter as constraint
>>>>>> i.M()
>>>>>> }
>>>>>>
>>>>>> func main() {}
>>>>>>
>>>>>> --
>>>>>> You received this message because you are subscribed to the Google
>>>>>> Groups "golang-nuts" group.
>>>>>> To unsubscribe from this group and stop receiving emails from it,
>>>>>> send an email to golang-nuts...@googlegroups.com.
>>>>>> To view this discussion on the web visit
>>>>>> https://groups.google.com/d/msgid/golang-nuts/9fc66e8e-3f99-4c3a-87f7-ce7c1a705cdcn%40googlegroups.com
>>>>>> <https://groups.google.com/d/msgid/golang-nuts/9fc66e8e-3f99-4c3a-87f7-ce7c1a705cdcn%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>>>> .
>>>>>>
>>>>> --
>>>> You received this message because you are subscribed to the Google
>>>> Groups "golang-nuts" group.
>>>> To unsubscribe from this group and stop receiving emails from it, send
>>>> an email to golang-nuts+unsubscr...@googlegroups.com.
>>>> To view this discussion on the web visit
>>>> https://groups.google.com/d/msgid/golang-nuts/a4ffdc09-02cf-47af-96fc-3ebde3fc5d10n%40googlegroups.com
>>>> <https://groups.google.com/d/msgid/golang-nuts/a4ffdc09-02cf-47af-96fc-3ebde3fc5d10n%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>>
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/CAHbs%3DNZVnhK2fV2R2NbtXvfsyV%3DfP1ToD0SoSBhf9%3Dr0d19gPg%40mail.gmail.com.
