Why are template alias parameters broken?

[Menshikov]

On Friday, 27 August 2021 at 19:00:27 UTC, Menshikov wrote:
> On Friday, 27 August 2021 at 18:47:56 UTC, Menshikov wrote:
>> It's work:
>>
>> ```d
>> template Foo(alias var)
>> {
>>     void inc() { var++; }
>> }
>>
>> void main()
>> {
>>     int v = 4;
>>     alias foo = Foo!(v);
>>     foo.inc();
>>     assert(v == 5);
>> }
>> ```
>> But it doesn't work:
>> ```d
>> template Foo(alias var)
>> {
>>     void inc() { var++; }
>> }
>>
>> void main()
>> {
>>     struct V{
>>       int a;
>>     }
>>     auto v = V(4);
>>     alias foo = Foo!(v.a);
>>     foo.inc();//err
>>     assert(v.a == 5);
>> }
>> ```
>> Hence this applies to Alias!() and AliasSeq!()
>
> And it doesn't work
> ```d
> template Foo(alias var)
> {
>     void inc() { var++; }//err
> }
>
> void main()
> {
>     static struct V{
>       int a;
>     }
>     auto v = V(4);
>     mixin Foo!(v.a)foo;//err
>     foo.inc();
>     assert(v.a == 5);
> }
> ```
We open it ourselves, and it works:
```d
void main()
{
     static struct V{
       int a;
     }
     auto v = V(4);
     void inc() { v.a++; }
     inc();
     assert(v.a == 5);
}
```