Help needed: immutable struct is a type modifier, and that's wrong and broken

[RazvanN]

On Thursday, 16 April 2020 at 04:28:35 UTC, Timon Gehr wrote:
> On 16.04.20 05:55, RazvanN wrote:
>> 
>> 
>> Additionally, I think that
>> 
>> static if(is(S == immutable T, T))
>> 
>> should also not pass.
>> 
>> The correct form should be
>> 
>> static if(is(S == immutable))
>> 
>> This way you express the fact that S is an immutably defined 
>> type (with a storage specifier), whereas in the first case you 
>> test if S is an immutably declared type (with a type 
>> constructor).
>
> So the proposal is to turn `is` into an even more convoluted 
> mess? :)
>
> Why should it even be possible to test for `immutable` on the 
> declaration? That seems like an implementation detail as the 
> only thing it achieves is that all members are marked that way.

I agree that this is kind of awkward, but things are confusing 
otherwise.

Do you agree that in this situation `static if (is(S == immutable 
T, T))` should not pass? Or should it pass and the `static 
assert(is(S == T))` should also pass? In that case, T should bind 
to an empty type, which D, as far as I know does not support at 
the moment.