map(Integer, ::Vector{Any}) throws

[simonster]

julia> map(Integer, Any[1, 2])
ERROR: MethodError: `one` has no method matching one(::Type{Any})
 in map at abstractarray.jl:379

[hayd]

Should this return Integer[1, 2]? If so, I have a fix (not the above commit).

[JeffBezanson]

Ideally no; it should return Int[1, 2]. However for empty arrays it could use the trick in your commit.

[hayd]

The example I was testing in my branch was Any[1, 2., Int8(3), UInt8(4)], though perhaps this is an unreasonable example. (map in abstractarray gets the eltype from the first element.)

[simonster]

Are these methods actually necessary? On my system, they don't actually seem any faster than the general map method:

julia> x = map(Float64, rand(Int, 100000000));

julia> @time for i = 1:10; map(Integer, x); end
elapsed time: 2.734174725 seconds (7629 MB allocated, 1.92% gc time in 9 pauses with 1 full sweep)

julia> @time for i = 1:10; invoke(map, (Any, Vector), Integer, x); end
elapsed time: 2.658263088 seconds (7629 MB allocated, 0.67% gc time in 9 pauses with 0 full sweep)

julia> @time for i = 1:10; map(Integer, x); end
elapsed time: 2.73453461 seconds (7629 MB allocated, 0.66% gc time in 9 pauses with 0 full sweep)

julia> @time for i = 1:10; invoke(map, (Any, Vector), Integer, x); end
elapsed time: 2.633010239 seconds (7629 MB allocated, 0.67% gc time in 9 pauses with 0 full sweep

[JeffBezanson]

Yes, it's definitely arguable that these definitions just complicate things and should use the same map as everything else. I think they originate from trying to get a better type for the empty array case.

[simonster]

We could use a comprehension, but that's just kicking the can down the road on #7258.

[vtjnash]

@JeffBezanson can we fix this now?