struct XY { union { int x, y; } }
struct AHolder {
	XY aa;
	void a(XY x) { aa = x; }
}
struct AB {
	AHolder aHolder;
	XY b;
	void a(XY x) { aHolder.a(x); }
}
struct Main {
	AB ab;

	void setB() { ab.b = XY(); }
	void f() {
		ab.a(XY.init);
		setB();
	}
}

$ dmd -c -inline arst.d
Segmentation fault

Any of the following semantics-preserving changes will fix it:

- Making Main.setB use XY.init instead of XY()
- Inlining ab.a(XY.init) into Main.f
- Inlining setB() into Main.f
- Inlining aHolder.a(x) into AB.a