It turned out that Nim's Option type is broken for `not nil` and
`requiresInit` types. It will report an udesired warning due to
the way `none` is defined. The `Result` type doesn't suffer from
this problem, so I've transitioned some APIs in NBC to use the
new `results.Opt[T]` type (alias of `Result[T, void]`).
Perhaps we should renamed `Result` to `Res` to make the naming
more consistent and to allow the code to more easily fit in the
80 character per-line budget.
Giovanni Petrantoni
Jacek Sieka
Zahary Karadjov