Improve readability

Author: MilesCranmer

src/BaseType.jl

@@ -30,8 +30,11 @@ base_numeric_type(x) = base_numeric_type(typeof(x))
 
 function _base_numeric_type(::Type{T}) where {T}
     params = T isa UnionAll ? T.body.parameters : T.parameters
-    return isempty(params) ? T : _base_numeric_type(first(params))
-    # TODO: deal with recursive types
+    if isempty(params)
+        return T
+    else
+        return _base_numeric_type(first(params))
+    end
 end
 
 end

test/unittests.jl

@@ -1,6 +1,6 @@
 using Test: @test, @testset, @inferred
 using BaseType: base_numeric_type
-using DualNumbers: DualNumbers
+using DualNumbers: DualNumbers, Dual
 using DynamicQuantities: DynamicQuantities
 using Measurements: ±
 using Unitful: Unitful
@@ -37,3 +37,13 @@ end
     y = Dual(1.0)Unitful.u"m/s"
     @test base_numeric_type(y) == Float64
 end
+
+struct Node{T}
+    child::Union{Node{T},Nothing}
+    value::T
+end
+
+@testset "Safe default behavior for recursive types" begin
+    c = Node{Int}(Node{Int}(nothing, 1), 2)
+    @test base_numeric_type(c) == Int
+end