[Issue 23414] Import order emits "Error: no size because of forward references"

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23414

Max Samukha <maxsamukha at gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |maxsamukha at gmail.com

--- Comment #6 from Max Samukha <maxsamukha at gmail.com> ---
(In reply to Walter Bright from comment #4)

> struct S
> {
>     static if (S.sizeof == 0)
>     {
>         int x;
>     }
> }
> 
> It's impossible for the compiler to resolve it. While the example looks
> trivial and ridiculous, sometimes these cases are hidden behind a thicket of
> complex templates.
> 

While there is often a real circular dependence, D still fails in many cases
when there is not, like:

```
struct S(alias self)
{
    alias Outer = __traits(parent, self);
    ref Outer outer() => *cast(Outer*)(cast(ubyte*)&this - self.offsetof);
}

struct S2
{
    S!s s;
}
```
Error: circular reference to variable `a.S2.s

It would be immensely cool if that worked.

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