Using `CartesianIndex` with Flux.jl

General Usage
, ,
1

Is it possible to use CartesianIndex with Flux.jl within a Flux.with_gradient block?

Specifically I have a::Vector{Float32} and b::Vector{CartesianIndex}, and a[b] is in the gradient block. When I used this I got

ERROR: LoadError: ArgumentError: unable to check bounds for indices of type CartesianIndex{2}
Stacktrace:
  [1] checkindex(::Type{Bool}, inds::Base.OneTo{Int64}, i::CartesianIndex{2})
    @ Base ./abstractarray.jl:751
  [2] checkindex
    @ ./abstractarray.jl:767 [inlined]
  [3] checkbounds
    @ ./abstractarray.jl:689 [inlined]
  [4] checkbounds
    @ ./abstractarray.jl:699 [inlined]
  [5] _getindex
    @ ./multidimensional.jl:955 [inlined]
  [6] getindex
    @ ./abstractarray.jl:1342 [inlined]
  [7] rrule
    @ ~/.julia/packages/ChainRules/14CDN/src/rulesets/Base/indexing.jl:63 [inlined]
  [8] rrule
    @ ~/.julia/packages/ChainRulesCore/Vsbj9/src/rules.jl:138 [inlined]
  [9] chain_rrule
    @ ~/.julia/packages/Zygote/55SqB/src/compiler/chainrules.jl:234 [inlined]
 [10] macro expansion
    @ ~/.julia/packages/Zygote/55SqB/src/compiler/interface2.jl:-1 [inlined]
 [11] _pullback(::Zygote.Context{false}, ::typeof(getindex), ::Matrix{Float16}, ::Vector{CartesianIndex})
    @ Zygote ~/.julia/packages/Zygote/55SqB/src/compiler/interface2.jl:81