[Issue 24270] New: Pointer to Nullable of recursive struct

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24270

          Issue ID: 24270
           Summary: Pointer to Nullable of recursive struct
           Product: D
           Version: D2
          Hardware: x86
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P1
         Component: phobos
          Assignee: nobody at puremagic.com
          Reporter: alexandre.bourquelot at ahrefs.com

```
import std.typecons;

struct RecursiveClass {
    int id;
    bool flag;
    Nullable!(RecursiveClass)* children;
}
```

This does not compile because the compiler is unable to infer the size of the
struct, but given that the third member is a pointer, it should work.

```
/usr/lib/ldc/x86_64-linux-gnu/include/d/core/internal/traits.d(345): Error:
unable to determine fields of `RecursiveClass` because of forward references
/usr/lib/ldc/x86_64-linux-gnu/include/d/std/traits.d(3343): Error: template
instance `core.internal.traits._hasIndirections!(RecursiveClass)` error
instantiating
```

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