format self-refrential (squash me into prev)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

src/tangent_types/abstract_zero.jl

@@ -173,7 +173,9 @@ end
     end
 end
 
-zero_tangent(primal::Tuple, _cache=nothing) = Tangent{typeof(primal)}(map(x->zero_tangent(x, _cache), primal)...)
+function zero_tangent(primal::Tuple, _cache=nothing)
+    return Tangent{typeof(primal)}(map(x -> zero_tangent(x, _cache), primal)...)
+end
 
 function zero_tangent(x::Array{P,N}, _cache=nothing) where {P,N}
     if (isbitstype(P) || all(i -> isassigned(x, i), eachindex(x)))
@@ -199,4 +201,6 @@ function guess_zero_tangent_type(::Type{<:Array{T,N}}) where {T,N}
 end
 
 # The following will fall back to `Any` if it is hard to infer
-guess_zero_tangent_type(::Type{T}) where {T} = Core.Compiler.return_type(zero_tangent, Tuple{T})
+function guess_zero_tangent_type(::Type{T}) where {T}
+    return Core.Compiler.return_type(zero_tangent, Tuple{T})
+end

test/tangent_types/abstract_zero.jl

@@ -283,7 +283,7 @@ end
             Link(data) = new(data)
         end
 
-        lk= Link(1.5)
+        lk = Link(1.5)
         lk.next = lk
 
         d = zero_tangent(lk)
@@ -305,7 +305,6 @@ end
         @test_broken d_ca[1] == 0.0
         @test_broken d_ca[2] === _ca
 
-
         # Idea: check if typeof(xs) <: eltype(xs), if so need to cache it before computing
         xs = Any[1.5]
         push!(xs, xs)