Review comments

src/broadcast.jl

@@ -32,7 +32,7 @@ else
 end
 
 invoke_broadcast!{F, N}(f::F, dest, As::Vararg{NullableArray, N}) =
-    invoke(broadcast!, Tuple{Function, AbstractArray, Vararg{AbstractArray, N}}, f, dest, As...)
+    invoke(broadcast!, Tuple{F, AbstractArray, Vararg{AbstractArray, N}}, f, dest, As...)
 
 """
     broadcast(f, As::NullableArray...)
@@ -58,11 +58,7 @@ function Base.broadcast{F, N}(f::F, As::Vararg{NullableArray, N})
     f2(x...) = lift(f, x...)
 
     T = _default_eltype(Base.Generator{ziptype(As...), ftype(f2, As...)})
-    if isleaftype(T) && !(T <: Nullable)
-        dest = similar(Array{eltype(T)}, broadcast_indices(As...))
-    else
-        dest = similar(NullableArray{eltype(T)}, broadcast_indices(As...))
-    end
+    dest = similar(NullableArray{eltype(T)}, broadcast_indices(As...))
     invoke_broadcast!(f2, dest, As...)
 end
 

src/lift.jl

@@ -4,7 +4,7 @@
     else
         U = Core.Inference.return_type(f, Tuple{eltype(x)})
         if isnull(x)
-            return Nullable{U}()
+            return isleaftype(U) ? Nullable{U}() : Nullable()
         else
             return Nullable(f(unsafe_get(x)))
         end
@@ -18,7 +18,7 @@ end
     else
         U = Core.Inference.return_type(f, Tuple{eltype(x1), eltype(x2)})
         if isnull(x1) | isnull(x2)
-            return Nullable{U}()
+            return isleaftype(U) ? Nullable{U}() : Nullable()
         else
             return Nullable(f(unsafe_get(x1), unsafe_get(x2)))
         end
@@ -53,7 +53,7 @@ return `f` applied to values of `xs`.
     else
         U = Core.Inference.return_type(f, eltypes(xs...))
         if hasnulls(xs...)
-            return Nullable{U}()
+            return isleaftype(U) ? Nullable{U}() : Nullable()
         else
             return Nullable(f(_unsafe_get(xs...)...))
         end

src/map.jl

@@ -1,7 +1,7 @@
 using Base: collect_similar, Generator
 
 invoke_map!{F, N}(f::F, dest, As::Vararg{NullableArray, N}) =
-    invoke(map!, Tuple{Function, AbstractArray, Vararg{AbstractArray, N}}, f, dest, As...)
+    invoke(map!, Tuple{F, AbstractArray, Vararg{AbstractArray, N}}, f, dest, As...)
 
 """
     map(f, As::NullableArray...)
@@ -27,11 +27,7 @@ function Base.map{F, N}(f::F, As::Vararg{NullableArray, N})
     f2(x...) = lift(f, x...)
 
     T = _default_eltype(Base.Generator{ziptype(As...), ftype(f2, As...)})
-    if isleaftype(T) && !(T <: Nullable)
-        dest = similar(Array{eltype(T)}, size(As[1]))
-    else
-        dest = similar(NullableArray{eltype(T)}, size(As[1]))
-    end
+    dest = similar(NullableArray{eltype(T)}, size(As[1]))
     invoke_map!(f2, dest, As...)
 end