Support for Base.OneTo(3)

[colinfang]

Shall we support Base.OneTo now that it becomes commonly used in Base.

m = Model()
@variable(m, 0 <= x[Base.OneTo(3), 1:2] <= 3, Int)

0≤x i,j≤3,∈ℤ,∀i∈{1,2,3},j∈{2}

@constraint(m, sum(x[:, 1]) == 1)
Failed attempt to index JuMPArray along dimension 1: Colon() ∉ Base.OneTo(3)

[mlubin]

What's the point of this if you can write 1:3?

[colinfang]

I want to define variables/constraints programmatically. I used to do it like the following because Julia recommends eachindex(x) over 1:length(x). However after v0.5 the former returns OneTo

m = Model()
idx = eachindex(A) # I could write idx = 1:length(A)

@variable(m, 0 <= x[idx, 1:2] <= 3, Int)
@constraint(m, sum(x[:, 1]) == 1)

[mlubin]

idx is not used in that example

[mlubin]

Anyway since OneTo is a range with "lower limit ... guaranteed (by the type system) to be 1" it's a potential solution for the type instability issue in #346. So it's possible to support, although I don't understand your use case.