Comment by WalterBright

D has a keyword prefix `debug`. So, one can write things like:

    ...
    debug if (x) printf("x: %d\n", x);
    ...

So, you can throw the -debug switch on the compiler and the debug code is enabled. For asserts,

    debug assert(lookMa);

and the check is only run when the -debug switch is done. It works remarkably well.

Another interesting property of `debug` is it turns off the safety checks in the target statement that follows it. Because, sometimes you just gotta do some unsafe tricks to figure out where your code went wrong.