BoundsError when String is indexed by an BitArray{1}

[diegozea]

I found this BoundsError trying to index an ASCIIString using a BitArray{1}:

julia> a = "ABC"
"ABC"

julia> b = [1,2,3].!=2
3-element BitArray{1}:
  true
 false
  true

julia> a[b]
ERROR: BoundsError: attempt to access 3-element Array{UInt8,1}:
 0x41
 0x42
 0x43
  at index [0]
 in anonymous at strings/basic.jl:43
 in sprint at ./iostream.jl:206
 in getindex at strings/basic.jl:42

julia> @which a[b]
getindex(s::AbstractString, v::AbstractArray{T,1}) at strings/basic.jl:42

...but using a Vector{Bool} is fine:

julia> a[[true, false, true]]
"AC"

julia> @which a[[true, false, true]]
getindex(s::ASCIIString, r::Array{T,1}) at ascii.jl:19

[StefanKarpinski]

Hmm. I'm not sure if logical indexing of strings is a good idea. Although it can actually be done efficiently.

[ivarne]

Ref #4763, where the same issue was raised for SubArray

[kshyatt]

Still happens on master.

[nalimilan]

Actually, no: now a[[true, false, true]] gives the same error, which at least is consistent. I'm not persuaded we need logical indexing of strings either, so what we could do is restrict the signature of getindex to ::AbstractVector{<:Integer} to make it a MethodError.