float type error in ^2

[CarloLucibello]

on julia 0.6 when taking powers of recorded Float32 array the result is a Float64 array

julia> a=Rec(rand(Float32,3))
S[3]113R

julia> AutoGrad.unbox(a)
3-element Array{Float32,1}:
 0.988303
 0.40873 
 0.371695

julia> AutoGrad.unbox(a.^2)
3-element Array{Float64,1}:
 0.976743
 0.16706 
 0.138157