explicit argument errors

Author: mcabbott

src/deprecations.jl

@@ -28,3 +28,6 @@ function zeros(dims...)
   Base.depwarn("Flux.zeros(size...) is deprecated, please use Flux.zeros32(size...) or Base.zeros(Float32, size...)", :ones)
 end
 zeros(T::Type, dims...) = Base.zeros(T, dims...)
+
+ones32(::Type, dims...) = throw(ArgumentError("Flux.ones32 is always Float32, use Base.ones to specify the element type"))
+zeros32(::Type, dims...) = throw(ArgumentError("Flux.zeros32 is always Float32, use Base.zeros to specify the element type"))