I've just fixed UFCS for the experimental type function branch

[Paul Backus]

On Thursday, 10 September 2020 at 17:05:02 UTC, Meta wrote:
>
> I'm curious, will this also work?
>
> size_t sizeOf(alias t)
> {
>     size_t result;
>     /* static? */ if (__traits(isScalar))
>     {
>         static if (is(t == int))
>             result += 32;
>         else static if (...)
>         ...
>     }
>     else static if (is(t == A[n], A, size_t n))
>         result += A.sizeOf * n
>     else static if (...)
>         ...
>     else
>         /* static? */ foreach (field; t.tupleof)
>             result += field.sizeOf
>
>     return result;
> }
>
> Basically, is the implementation at a level where sizeOf can be 
> turtles all the way down, with minimal or no reliance on 
> __traits?

One thing built-in .sizeof does that no user-code version can do 
is "freeze" the size of a type to prevent additional members from 
being added. For example, if you try to compile this code:

struct S
{
     int a;
     enum size = S.sizeof;
     mixin("int b;");
}

...you'll get an error:

onlineapp.d-mixin-5(5): Error: variable onlineapp.S.b cannot be 
further field because it will change the determined S size