optimize +

src/rulesets/Base/indexing.jl

@@ -111,6 +111,17 @@ Base.size(A::OneElement) = map(length, A.axes)
 Base.axes(A::OneElement) = A.axes
 Base.getindex(A::OneElement{T,N}, i::Vararg{Int,N}) where {T,N} = ifelse(i==A.ind, A.val, zero(T))
 
+function ChainRulesCore.add!!(xs::AbstractArray{<:Any,N}, oe::OneElement{<:Any,N}) where {N}
+    if !ChainRulesCore.is_inplaceable_destination(xs)
+        xs = collect(xs)
+    end
+    xs[oe.ind...] += oe.val
+    return xs
+end
+
+Base.:(+)(xs::AbstractArray, oe::OneElement) = add!!(copy(xs), oe)
+Base.:(+)(oe::OneElement, xs::AbstractArray) = +(xs, oe)
+Base.:(+)(oe1::OneElement, oe2::OneElement) = +(collect(oe1), oe2)
 
 """
     _setindex_zero(x, dy, inds...)