How is this code invalid?

[Ali Çehreli]

On 12/16/22 18:20, H. S. Teoh wrote:

 > scratch space for computations, called the runtime
 > stack.

I called it "function call stack" where I gave a very simplistic view of 
it here:

   https://www.youtube.com/watch?v=NWIU5wn1F1I&t=236s

 > (2) Use @safe when possible so that the compiler will tell you when
 > you're doing something wrong and potentially dangerous.

Unfortunately, @safe is not as prominent in the book as it should be. 
Part of the reason is I think its implementation is not complete 
especially how it changes with -dip1000.

Ali