Function 'atvalue' cannot handle negative ranges

Dear all,

I recently noticed an inconvenient issue with the atvalue function, namely that it does not work for negatively iterated ranges/units. Here's an example:

using AxisArrays
using Unitful: mm

AA = AxisArray(reshape(1:11^2, (11, 11)),
    Axis{:x}(-5mm:1mm:5mm),     # positive
    Axis{:y}(5mm:-1mm:-5mm))    # negative

# positive direction
println(AA[x = atvalue(1mm)])
# negative direction
println(AA[y = atvalue(1mm)])

While the instantiation of the AxisArray and the first example in the positive direction (x-axis) work perfectly fine, the latter in the negative direction (y-axis) fails and prints the following error message:

ERROR: LoadError: BoundsError: attempt to access 11-element StepRange{Unitful.Quantity{Int64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}}, Unitful.Quantity{Int64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}}} at index [TolValue(1 mm, tol=0 mm)]
Stacktrace:
  [1] axisindexes(#unused#::Type{AxisArrays.Dimensional}, ax::StepRange{Unitful.Quantity{Int64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}}, Unitful.Quantity{Int64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}}}, idx::AxisArrays.TolValue{Unitful.Quantity{Int64, 𝐋, Unitful.FreeUnits{(mm,), 𝐋, nothing}}})
    @ AxisArrays ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:234
  [2] axisindexes
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:199 [inlined]
  [3] macro expansion
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:394 [inlined]
  [4] _to_index
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:349 [inlined]
  [5] to_index
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:347 [inlined]
  [6] macro expansion
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:153 [inlined]
  [7] to_index
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:141 [inlined]
  [8] getindex
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:123 [inlined]
  [9] #getindex#38
    @ ~/.julia/packages/AxisArrays/v7vf4/src/indexing.jl:164 [inlined]
 [10] top-level scope

I wonder if there is a simple solution to that problem (am I doing something wrong?) or if this undesired behavior needs to be fixed inside of the package.

Kindly,
EminentCoder

PS: Unitful does not contribute to the error, the problem remains without the units as well.

Start in src/indexing.jl around axisindexes, especially the logic reported at line 234, and run the provided reproducer with both ordinary ranges and Unitful ranges. The issue is done when atvalue works for descending ranges while the existing ascending-range behavior continues to pass.