From 45f00a5168ac64ce2eb147c0ae853095e071cc63 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 15 Sep 2024 23:34:27 -0400
Subject: [PATCH] Add promotion rules (belong in ChainRulesCore)

---
 src/rulesets/Base/indexing.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/rulesets/Base/indexing.jl b/src/rulesets/Base/indexing.jl
index 8c5865a98..e2523a8fa 100644
--- a/src/rulesets/Base/indexing.jl
+++ b/src/rulesets/Base/indexing.jl
@@ -284,6 +284,10 @@ end
 
 _zero_fill!(dx::AbstractArray) = fill!(dx, zero(eltype(dx)))
 
+# Belong in ChainRulesCore
+Base.promote_type(T::Type{<:Number}, S::Type{<:AbstractZero}) = T
+Base.promote_type(T::Type{<:AbstractZero}, S::Type{<:Number}) = S
+
 function rrule(::typeof(∇eachslice), dys, x, vd::Val)
     function ∇∇eachslice(dz_raw)
         dz = unthunk(dz_raw)