static void TestStructCasts()
{
PromotedStruct a = new PromotedStruct(); // Addr-exposed, cannot be independent promoted.
a.anotherField = 5;
a.smallField = 6;
Debug.Assert(PromotedStruct.AsNotPromotedStruct(ref a).anotherField == 0x5);
// This access will ask LclVariable with type of `PromotedStruct` about the field with offset == 4, that doesn't exist there.
Debug.Assert(PromotedStruct.AsNotPromotedStruct(ref a).overlappingField == 0x600000000);
a.smallField = 6;
Debug.Assert(PromotedStruct.AsNotPromotedStruct(ref a).overlappingField == 0x600000000);
PromotedStruct.AsNotPromotedStruct(ref a).overlappingField = 0x700000000;
Debug.Assert(a.smallField == 0x7);
}
static void TestStructCasts()
{
PromotedStruct a = new PromotedStruct(); // Addr-exposed, cannot be promoted.promotedField.
a.promotedField.pointerSizedField = 4;
a.anotherField = 5;
NotPromotedStruct b = PromotedStruct.AsNotPromotedStruct(ref a);
// The cast can be inlined and the field handle will refer to the `PromotedStruct.pointerSizedField`,
// in this case we can promote it because `NotPromotedStruct.notPromotedField.pointerSizedField` has
// the same class handle.
Debug.Assert(b.notPromotedField.pointerSizedField == 0x4);
NotPromotedStruct c = PromotedStruct.AsNotPromotedStruct(ref a);
// The cast can be inlined and the field handle will refer to the `PromotedStruct.pointerSizedField`,
// in this case we cannot promote it because `NotPromotedStruct.anotherOverlappingStruct.a` has
// a different class handle (`NotPromotedStruct.anotherOverlappingStruct`).
Debug.Assert(c.anotherOverlappingStruct.a == 0x4);
Debug.Assert(c.anotherOverlappingStruct.b == 0x5);
}
public static ref NotPromotedStruct AsNotPromotedStruct(ref PromotedStruct d) => ref Unsafe.As <PromotedStruct, NotPromotedStruct>(ref d);