cannot assign to ustriped AbstractArrays

[bjarthur]

it sure would be nice if Unitful played better with CuArrays. for example, currently, one cannot ustrip a CuArray and then assign to it:

julia> using Unitful, CUDA

julia> c = CuArray(zeros(3) * 1u"s")
3-element CuArray{Quantity{Float64, 𝐓, Unitful.FreeUnits{(s,), 𝐓, nothing}}, 1, CUDA.Mem.DeviceBuffer}:
 0.0 s
 0.0 s
 0.0 s

julia> ustrip(c)[1]=1   # innocuous warning about scalar indexing removed for succinctness
1

julia> c
3-element CuArray{Quantity{Float64, 𝐓, Unitful.FreeUnits{(s,), 𝐓, nothing}}, 1, CUDA.Mem.DeviceBuffer}:
 0.0 s
 0.0 s
 0.0 s

however, if i simply add a new method identical to this one but with CuArray, then it works fine:

julia> import Unitful: ustrip

julia> @inline ustrip(A::CuArray{Q}) where {Q <: Quantity} = reinterpret(Unitful.numtype(Q), A)
ustrip (generic function with 16 methods)

julia> ustrip(c)[1]=1
1

julia> c
3-element CuArray{Quantity{Float64, 𝐓, Unitful.FreeUnits{(s,), 𝐓, nothing}}, 1, CUDA.Mem.DeviceBuffer}:
 1.0 s
 0.0 s
 0.0 s

to be all inclusive, i think the right way to go here is just use AbstractArray. then it'll work too for MtlArray, ROCArray, etc.

Originally posted by @bjarthur in #630 (comment)