From 42fc75d5f5273db041c1302beceaf7b892f49e4a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Tue, 15 Oct 2024 16:19:04 +0200
Subject: [PATCH] Add comments

---
 src/dispatch.jl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/dispatch.jl b/src/dispatch.jl
index 10dbc6d..1db2dac 100644
--- a/src/dispatch.jl
+++ b/src/dispatch.jl
@@ -15,10 +15,13 @@ abstract type AbstractMutable end
 
 function Base.sum(
     a::AbstractArray{T};
-    dims = missing,
+    dims = :,
     init = zero(promote_operation(+, T, T)),
 ) where {T<:AbstractMutable}
     if !ismissing(dims)
+        # We cannot use `mapreduce` with `add!!` instead of `Base.add_mul` like
+        # `operate(sum, ...)` because the same instance given at `init` is used
+        # at several places.
         return mapreduce(identity, Base.add_sum, a; dims, init)
     end
     return operate(sum, a; init)