I recently played around with atomic operations. While doing so,
I noticed a problem with the interaction of interfaces and cas.
Consider the following program:
```
import core.atomic;
import std.stdio;
interface TestInterface
{
}
class TestClass : TestInterface
{
}
void main()
{
shared TestInterface testInterface = new shared TestClass;
cas(&testInterface, testInterface, new shared
TestClass).writeln;
writeln(typeid(testInterface));
}
```
(https://run.dlang.io/is/9P7PAb)
This program compiles successfully and outputs
```
true
Error: program killed by signal 11
```
i.e. a segmentation fault happens.
When replacing "interface" with "abstract class"
(https://run.dlang.io/is/sFaO1k), everything works as expected
and the program outputs
```
true
onlineapp.TestClass
```
Is this actually a bug or a fundamental limitation of cas and
interfaces? Did I do anything wrong?
