[Issue 18493] [betterC] Can't use aggregated type with postblit

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18493

--- Comment #3 from Radu Racariu <radu.racariu at gmail.com> ---
Declaring `C` as 

---
struct C
{
    S s1;
}
---

makes the test case compile.

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