I know that :-) The point is that only the bottom most code above compiling with --gc:arc give us the desired compile-time error. The topmost code compiles always without error, the bottom most code compiles with default gc.
Well, it is indeed good enough, our actual code should most of the time look like the bottom most code, and we can compile always with --gc:arc to check for errors even when we intent to use another GC.
