address review

Author: oscardssmith

src/algorithms/trust_region.jl

@@ -24,13 +24,16 @@ function TrustRegion(; concrete_jac = nothing, linsolve = nothing, precs = DEFAU
         initial_trust_radius::Real = 0 // 1, step_threshold::Real = 1 // 10000,
         shrink_threshold::Real = 1 // 4, expand_threshold::Real = 3 // 4,
         shrink_factor::Real = 1 // 4, expand_factor::Real = 2 // 1,
-        max_shrink_times::Int = 32, autodiff = nothing, vjp_autodiff = autodiff)
+        max_shrink_times::Int = 32, autodiff = nothing, vjp_autodiff = nothing)
     descent = Dogleg(; linsolve, precs)
     if autodiff isa Union{ADTypes.AbstractForwardMode, ADTypes.AbstractFiniteDifferencesMode}
         forward_ad = autodiff
     else
         forward_ad = nothing
     end
+    if isnothing(vjp_autodiff) && autodiff isa ADTypes.AbstractFiniteDifferencesMode
+        vjp_autodiff = autodiff
+    end
     trustregion = GenericTrustRegionScheme(; method = radius_update_scheme, step_threshold,
         shrink_threshold, expand_threshold, shrink_factor, expand_factor,
         reverse_ad = vjp_autodiff, forward_ad)