Fix GPU getindex

[mcabbott]

Before:

julia> @allowscalar cx[1,1]
ERROR: MethodError: getindex(::OneHotMatrix{UInt32, JLArray{UInt32, 1}}, ::Int64, ::Int64) is ambiguous.

Candidates:
  getindex(x::OneHotArray{var"#s3", N, var"N+1", I} where {var"#s3", var"N+1", I<:Union{AbstractArray{var"#s3", N}, var"#s3"}}, i::Int64, I::Vararg{Int64, N}) where N
    @ OneHotArrays ~/.julia/packages/OneHotArrays/0JMW1/src/array.jl:65
  getindex(x::OneHotArray{<:Any, N, <:Any, <:GPUArraysCore.AbstractGPUArray}, i::Int64, I::Vararg{Any, N}) where N
    @ OneHotArrays ~/.julia/packages/OneHotArrays/0JMW1/src/array.jl:71

Possible fix, define
  getindex(::OneHotArray{var"#s3", N, <:Any, <:Union{…}} where var"#s3", ::Int64, ::Vararg{Int64, N}) where N

Stacktrace:
 [1] macro expansion
   @ ~/.julia/packages/GPUArraysCore/GMsgk/src/GPUArraysCore.jl:210 [inlined]
 [2] top-level scope
   @ REPL[64]:1
Some type information was truncated. Use `show(err)` to see complete types.

julia> @allowscalar collect(cx)
ERROR: MethodError: getindex(::OneHotMatrix{UInt32, JLArray{UInt32, 1}}, ::Int64, ::Int64) is ambiguous.

julia> x = onehotbatch(rand(1:99, 100), 1:100);

julia> @btime Matrix($x);
  8.958 μs (3 allocations: 10.08 KiB)

After:

julia> @allowscalar cx[1,1]
true

julia> collect(cx)
3×4 Matrix{Bool}:
 1  0  0  0
 0  1  0  1
 0  0  1  0

julia> convert(AbstractArray{Float32}, cx)
3×4 JLArray{Float32, 2}:
 1.0  0.0  0.0  0.0
 0.0  1.0  0.0  1.0
 0.0  0.0  1.0  0.0

julia> x = onehotbatch(rand(1:99, 100), 1:100);

julia> @btime Matrix($x);
  2.375 μs (4 allocations: 10.12 KiB)

Unchanged is the need for @allowscalar in order to get a column:

julia> @allowscalar cx[:,4]
3-element OneHotVector(::UInt32) with eltype Bool:
 ⋅
 1
 ⋅

julia> cx[:,4]
ERROR: Scalar indexing is disallowed.

[mcabbott]

Maybe @ExpandingMan wants to review?

[ExpandingMan]

Sorry, I had forgotten about this, but it was still in my list of github notifications so I came back to it.

Yes, this looks good to me. Certainly an improvement.

[mcabbott]

Ok let's do this.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.00%. Comparing base (0ea288d) to head (49fd2ea).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #53      +/-   ##
==========================================
- Coverage   96.26%   95.00%   -1.27%     
==========================================
  Files           3        3              
  Lines         134      160      +26     
==========================================
+ Hits          129      152      +23     
- Misses          5        8       +3     

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