unsafe_convert fails for array views with non-Int indices

[nalimilan]

This was reported at JuliaStats/Distances.jl#227. unsafe_convert appears to require SubArray inputs to have Int indices. This is due to the use of RangeIndex in the signature. Is there any reason not to support other integer types?

julia> data = rand(100);

julia> my_view = @view data[1:UInt64(50)];

julia> Base.unsafe_convert(Ptr{Float64}, my_view)
ERROR: conversion to pointer not defined for SubArray{Float64, 1, Vector{Float64}, Tuple{UnitRange{UInt64}}, true}
Stacktrace:
 [1] error(s::String)
   @ Base ./error.jl:33
 [2] unsafe_convert(#unused#::Type{Ptr{Float64}}, a::SubArray{Float64, 1, Vector{Float64}, Tuple{UnitRange{UInt64}}, true})
   @ Base ./pointer.jl:67
 [3] top-level scope
   @ REPL[20]:1

(FWIW RangeIndex is a very old alias, it was even was originally written Union(Int, Range{Int}, UnitRange{Int}, Colon).)

[mkitti]

I think the solution to this is #43262