NaNs Just Don't Get No Respect

[bearophile]

Walter Bright:

> Oh come on. That's called a "user defined type."

This D code compiles and it throws an "Enforcement failed" 
Exception at runtime:

import std.typecons: Nullable;
void main() {
     Nullable!int x;
     int y = x;
}


With a different type system the compiler makes sure at 
compile-time that x is not empty (this means the compiler makes 
sure in no code paths x is used before testing it contains 
something), avoiding the run-time exception.

Bye,
bearophile