Fix #3790

Author: timholy

base/abstractarray.jl

@@ -21,7 +21,7 @@ isfloat64{T<:Float32,n}(x::AbstractArray{T,n}) = true
 ndims{T,n}(::AbstractArray{T,n}) = n
 ndims{T,n}(::Type{AbstractArray{T,n}}) = n
 ndims{T<:AbstractArray}(::Type{T}) = ndims(super(T))
-length(t::AbstractArray) = prod(size(t))
+length(t::AbstractArray) = prod(size(t))::Int
 endof(a::AbstractArray) = length(a)
 first(a::AbstractArray) = a[1]
 last(a::AbstractArray) = a[end]