RFC: Value range propagation for if-else

[bearophile via Digitalmars-d]

Nordlöw:

> Note that my discussion so far is about inhibiting run-time 
> checknig of the value range of
>
> struct Bound(T,
>              B = T, // bounds type
>              B lower = B.min,
>              B upper = B.max,
>              bool optional = false,
>              bool exceptional = true)

OK. But how?

Bye,
bearophile