Avoid recursion heuristic (#574)

Author: chriselrod

Project.toml

@@ -1,6 +1,6 @@
 name = "ForwardDiff"
 uuid = "f6369f11-7733-5829-9624-2563aa707210"
-version = "0.10.24"
+version = "0.10.25"
 
 [deps]
 CommonSubexpressions = "bbf7d656-a473-5ed7-a52c-81e309532950"

src/dual.jl

@@ -380,9 +380,9 @@ for R in (Irrational, Real, BigFloat, Bool)
     end
 end
 
-Base.convert(::Type{Dual{T,V,N}}, d::Dual{T}) where {T,V,N} = Dual{T}(convert(V, value(d)), convert(Partials{N,V}, partials(d)))
-Base.convert(::Type{Dual{T,V,N}}, x) where {T,V,N} = Dual{T}(convert(V, x), zero(Partials{N,V}))
-Base.convert(::Type{Dual{T,V,N}}, x::Number) where {T,V,N} = Dual{T}(convert(V, x), zero(Partials{N,V}))
+@inline Base.convert(::Type{Dual{T,V,N}}, d::Dual{T}) where {T,V,N} = Dual{T}(V(value(d)), convert(Partials{N,V}, partials(d)))
+@inline Base.convert(::Type{Dual{T,V,N}}, x) where {T,V,N} = Dual{T}(V(x), zero(Partials{N,V}))
+@inline Base.convert(::Type{Dual{T,V,N}}, x::Number) where {T,V,N} = Dual{T}(V(x), zero(Partials{N,V}))
 Base.convert(::Type{D}, d::D) where {D<:Dual} = d
 
 Base.float(::Type{Dual{T,V,N}}) where {T,V,N} = Dual{T,float(V),N}

test/AllocationsTest.jl

@@ -4,6 +4,8 @@ using ForwardDiff
 
 include(joinpath(dirname(@__FILE__), "utils.jl"))
 
+convert_test_574() = convert(ForwardDiff.Dual{Nothing,ForwardDiff.Dual{Nothing,ForwardDiff.Dual{Nothing,Float64,8},4},2}, 1.3)
+
 @testset "Test seed! allocations" begin
     x = rand(1000)
     cfg = ForwardDiff.GradientConfig(nothing, x)
@@ -28,6 +30,11 @@ include(joinpath(dirname(@__FILE__), "utils.jl"))
     alloc = @allocated ForwardDiff.seed!(duals, x, index, seed)
     alloc = @allocated ForwardDiff.seed!(duals, x, index, seed)
     @test alloc == 0
+    
+    alloc = @allocated convert_test_574()
+    alloc = @allocated convert_test_574()
+    @test alloc == 0
+  
 end
 
-end
+end