JuliaLang/julia — pull request #9351 by amitmurthy (2014-12-14 04:56:49+00:00)
Title: additional convert methods for Nullable

Allows for :
```
julia> type Bar
a::Nullable{Int}
b::Nullable{Bool}

Bar() = new(nothing, nothing)
end

julia> bar=Bar()
Bar(Nullable{Int64}(),Nullable{Bool}())

julia> bar.a=1
Nullable(1)

julia> bar.a=nothing
Nullable{Int64}()

```