SIGSEGV: Illegal storage access. (Attempt to read from nil?) in coroutines

[termer]

For future reference by anyone who has been burned by buggy async and high 
memory usage (and lack of working coroutines in the stdlib), CPS is the only 
real alternative that actually works efficiently and properly. I hope that 
they'll eventually be implemented in the compiler, because I keep seeing these 
discussions pop up and they always end up the same way.