set(arr, reverse, arr2) can change size

[jariji]

Allow reversed objects to change size. E.g.

julia> @modify([10,20,30]) do xs
           xs[2:3]
       end
2-element Vector{Int64}:
 20
 30

Resolves #212.

[jariji]

I'm not sure why set isn't hitting the method in the extension. If I define those methods directly in the repl the right one is selected and the test passes.

julia> using AxisKeys,Accessors, Test

julia> function Accessors.set(x::AbstractVector, ::typeof(reverse), v)
           res = similar(x, eltype(v))
           res .= v
           reverse!(res)
           res
       end
       function Accessors.set(x::AbstractVector, ::typeof(reverse), v::AbstractVector)
           res = similar(x, eltype(v), size(v))
           res .= v
           reverse!(res)
           res
       end
       function Accessors.set(x::AxisKeys.KeyedArray, ::typeof(reverse), v::AbstractVector)
           res = similar(x, eltype(v))
           res .= v
           reverse!(res)
           res
       end
       let
           C = KeyedArray([1,2,3], x=[:a, :b, :c])
           @test (@set reverse(C) = [5,6,7])::KeyedArray == KeyedArray([7,6,5], x=[:a, :b, :c])
       end
Test Passed

[aplavin]

Thanks for trying it out @jariji!

It's not just KeyedArrays that need special handling after this PR. For example, StaticArrays now lose their "staticness" completely: set(SVector(1,2,3), reverse, 10:12) now returns a plain Vector without a static length.
Maybe there are even more cases like that... But even with 2 major "special cases", I'm personally not fully convinced this is the way to go.

[aplavin]

But the extension issue itself is simple: you should define a new set function that doesn't overload Accessors.set.