Bug casting Inf to Interval

[dpsanders]

julia> convert(Interval, ∞)
[∞, ∞]

[dpsanders]

Also

julia> Interval{Float64}(∞)
[∞, ∞]

This is a prohibited interval. We could either throw an error or return Interval(prevfloat(Inf), Inf).

[lbenet]

I'm in favor of throwing an error here; in whatever interpretation of an Interval, it simply makes no sense.

In pass, note that atomic yields your last solution

julia> IntervalArithmetic.atomic(Interval{Float64}, ∞)
[1.79769e+308, ∞]