Replace NO_FIELDS by NoTangent() (#163)

Author: mzgubic

src/rand_tangent.jl

@@ -35,17 +35,13 @@ function rand_tangent(rng::AbstractRNG, x::T) where {T}
     end
 
     field_names = fieldnames(T)
-    if length(field_names) > 0
-        tangents = map(field_names) do field_name
-            rand_tangent(rng, getfield(x, field_name))
-        end
-        if all(tangent isa NoTangent for tangent in tangents)
-            # if none of my fields can be perturbed then I can't be perturbed
-            return NoTangent()
-        else
-            Tangent{T}(; NamedTuple{field_names}(tangents)...)
-        end
+    tangents = map(field_names) do field_name
+        rand_tangent(rng, getfield(x, field_name))
+    end
+    if all(tangent isa NoTangent for tangent in tangents)
+        # if none of my fields can be perturbed then I can't be perturbed
+        return NoTangent()
     else
-        return NO_FIELDS
+        Tangent{T}(; NamedTuple{field_names}(tangents)...)
     end
 end

test/rand_tangent.jl

@@ -40,7 +40,7 @@ using FiniteDifferences: rand_tangent
         # structs.
         (Foo(5.0, 4, rand(rng, 3)), Tangent{Foo}),
         (Foo(4.0, 3, Foo(5.0, 2, 4)), Tangent{Foo}),
-        (sin, typeof(NO_FIELDS)),
+        (sin, NoTangent),
         # all fields NoTangent implies NoTangent
         (Pair(:a, "b"), NoTangent),
         (1:10, NoTangent),