promote fails with BitArrays

[cossio]

promote(randn(4,5), bitrand(2,2))

ERROR: promotion of types Matrix{Float64} and BitMatrix failed to change any arguments
Stacktrace:
[1] error(::String, ::String, ::String)
@ Base ./error.jl:42
[2] sametype_error(input::Tuple{Matrix{Float64}, BitMatrix})
@ Base ./promotion.jl:374
[3] not_sametype(x::Tuple{Matrix{Float64}, BitMatrix}, y::Tuple{Matrix{Float64}, BitMatrix})
@ Base ./promotion.jl:368
[4] promote(x::Matrix{Float64}, y::BitMatrix)
@ Base ./promotion.jl:351
[5] top-level scope
@ REPL[5]:1

Contrast that with,

julia> promote(randn(4,5), rand(-3:3, 2,2))

([1.0404679330906446 0.13605200544037485 … 0.6584649350909583 1.759298096581398; 0.8577584331870316 -0.9385873914104255 … -0.7270472742833658 0.42998694669894727; -1.3226103979280828 1.2291060826052171 … 2.4340481349552263 -0.3980550678017092; 0.3515606302511447 -0.2598112417308294 … -0.2447667146035612 -1.6238446588858528], [2.0 2.0; 0.0 0.0])

[JakobSachs]

I think its failing because theres no definition of a Promotion rule (promote_rule()) for BitMatrix, Matrix.
Something i tried and that seems to work is to create a new rule like:

julia> using Random

julia> import Base.promote_rule

julia> promote_rule(::Type{BitMatrix},::Type{Matrix{T}}) where {T} = Matrix{T}
promote_rule (generic function with 125 methods)

julia> promote(bitrand(2,2),randn(2,2))
([1.0 0.0; 0.0 1.0], [1.3555790148282878 1.1034170972100035; 0.2637702233227674 -0.8688494447101851])

julia> 

This is just the first thing i tried, so there has to be a better way to write it and make it more general (including BitArray/BitVector).

So one fix would be to include a promote_rule for BitMatrix and BitArray in base/bitarray.jl.

Maybe i'm also missing something but thats what i came up with by quickly looking over it.

Edit:

I tried using a rule like:

julia> promote_rule(::Type{BitArray},::Type{Array})= Array                                                              
promote_rule (generic function with 126 methods)                                                                                                                                                                                                                                                                                                                                                                                                                                          

in an attempt to make a generalized rule, but it doesn't seem to work:

julia> promote(BitArray([1,0,1]),Array([1,3,4]))                                                                        
ERROR: promotion of types BitVector and Vector{Int64} failed to change any arguments                                    
Stacktrace:                                                                                                              
 [1] error(::String, ::String, ::String)                                                                                   
  @ Base .\error.jl:42                                                                                                 
 [2] sametype_error(input::Tuple{BitVector, Vector{Int64}})                                                              
  @ Base .\promotion.jl:316                                                                                            
 [3] not_sametype(x::Tuple{BitVector, Vector{Int64}}, y::Tuple{BitVector, Vector{Int64}})                                
  @ Base .\promotion.jl:310                                                                                            
 [4] promote(x::BitVector, y::Vector{Int64})                                                                             
  @ Base .\promotion.jl:293                                                                                            
 [5] top-level scope                                                                                                     
  @ REPL[22]:1