split create_bias into two

src/utils.jl

@@ -297,16 +297,20 @@ Return a bias parameter for a layer, based on the value given
 to the constructor's keyword `bias=bias`.
 
 * `bias == true` creates a zero vector, of the same type as weights.
-* `bias == false` returns `Zeros()`, a special struct which exists to encode the absence of bias.
+* `bias == false` returns `Zeros()`, a special struct which exists only to encode the absence of bias.
 * `bias::AbstractArray` uses the array provided, provided it has the correct size and eltype. If the type is wrong, it will be converted.
 """
-function create_bias(weights::AbstractArray{T}, bias::Union{Bool, AbstractArray}, dims::Integer...) where {T}
-  bias===true && return fill!(similar(weights, dims...), 0)
-  bias===false && return Zeros()
-  size(bias) == dims || throw(DimensionMismatch("expected bias of size $dims, but got $(size(bias))"))
-  eltype(bias) == T && return bias
-  @warn "converting bias to match element type of weights" typeof(weights) typeof(bias) maxlog=3 _id=hash(dims)
-  return T.(bias)
+function create_bias(weights::AbstractArray, bias::Bool, dims::Integer...)
+  bias ? fill!(similar(weights, dims...), 0) : Zeros()
+end
+function create_bias(weights::AbstractArray, bias::AbstractArray, dims::Integer...)
+  size(bias) == dims || throw(DimensionMismatch("expected bias of size $(dims), got size $(size(bias))"))
+  if eltype(bias) == eltype(weights)
+    return bias
+  else
+    @warn "converting bias to match element type of weights" typeof(weights) typeof(bias) maxlog=3 _id=hash(dims)
+    return broadcast(eltype(weights), bias)
+  end
 end
 
 """