Update eltype computation code to match Base

These have recently been simplified. map() in Base does not use
the same path as broadcast(), but doing so here is much simpler
and results should be equivalent for consistency anyway.

src/broadcast.jl

@@ -9,16 +9,12 @@ else
  const broadcast_indices = broadcast_shape
 end
 
-if !isdefined(Base.Broadcast, :ftype) # Julia < 0.6
+if VERSION < v"0.6.0-dev" # Old approach needed for inference to work
  ftype(f, A) = typeof(f)
  ftype(f, A...) = typeof(a -> f(a...))
  ftype(T::DataType, A) = Type{T}
  ftype(T::DataType, A...) = Type{T}
-else
- using Base.Broadcast: ftype
-end
 
-if !isdefined(Base.Broadcast, :ziptype) # Julia < 0.6
  if isdefined(Base, :Iterators)
  using Base.Iterators: Zip2
  else
@@ -27,8 +23,19 @@ if !isdefined(Base.Broadcast, :ziptype) # Julia < 0.6
  ziptype(A) = Tuple{eltype(A)}
  ziptype(A, B) = Zip2{Tuple{eltype(A)}, Tuple{eltype(B)}}
  @inline ziptype(A, B, C, D...) = Zip{Tuple{eltype(A)}, ziptype(B, C, D...)}
+
+ nullable_broadcast_eltype(f, As...) =
+ _default_eltype(Base.Generator{ziptype(As...), ftype(f, As...)})
 else
- using Base.Broadcast: ziptype
+ Base.@pure nullable_eltypestuple(a) = Tuple{eltype(eltype(a))}
+ Base.@pure nullable_eltypestuple(T::Type) = Tuple{Type{eltype(T)}}
+ Base.@pure nullable_eltypestuple(a, b...) =
+ Tuple{nullable_eltypestuple(a).types..., nullable_eltypestuple(b...).types...}
+
+ Base.@pure function nullable_broadcast_eltype(f, As...)
+ T = Core.Inference.return_type(f, nullable_eltypestuple(As...))
+ T === Union{} ? Any : T
+ end
 end
 
 invoke_broadcast!{F, N}(f::F, dest, As::Vararg{NullableArray, N}) =
@@ -57,7 +64,7 @@ function Base.broadcast{F}(f::F, As::NullableArray...)
  @inline f2(x1, x2, x3, x4, x5, x6, x7) = lift(f, (x1, x2, x3, x4, x5, x6, x7))
  @inline f2(x...) = lift(f, x)
 
- T = _default_eltype(Base.Generator{ziptype(As...), ftype(f2, As...)})
+ T = nullable_broadcast_eltype(f, As...)
  dest = similar(NullableArray{eltype(T)}, broadcast_indices(As...))
  invoke_broadcast!(f2, dest, As...)
 end

src/map.jl

@@ -1,5 +1,3 @@
-using Base: collect_similar, Generator
-
 invoke_map!{F, N}(f::F, dest, As::Vararg{NullableArray, N}) =
  invoke(map!, Tuple{F, AbstractArray, Vararg{AbstractArray, N}}, f, dest, As...)
 
@@ -26,7 +24,7 @@ function Base.map{F}(f::F, As::NullableArray...)
  @inline f2(x1, x2, x3, x4, x5, x6, x7) = lift(f, (x1, x2, x3, x4, x5, x6, x7))
  @inline f2(x...) = lift(f, x)
 
- T = _default_eltype(Base.Generator{ziptype(As...), ftype(f2, As...)})
+ T = nullable_broadcast_eltype(f, As...)
  dest = similar(NullableArray{eltype(T)}, size(As[1]))
  invoke_map!(f2, dest, As...)
 end