From af1b3e77ccd02d62572289c9286b6cec404d1ae1 Mon Sep 17 00:00:00 2001
From: odow <o.dowson@gmail.com>
Date: Wed, 24 Apr 2024 16:35:49 +1200
Subject: [PATCH] Implement Base.zero(::Type{MA.Zero})

---
 src/rewrite.jl  | 4 ++++
 test/rewrite.jl | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/rewrite.jl b/src/rewrite.jl
index 9c054a61..44d43a75 100644
--- a/src/rewrite.jl
+++ b/src/rewrite.jl
@@ -30,6 +30,10 @@ end
 
 struct Zero end
 
+# This method is called in various `promote_operation_fallback` methods if one
+# of the arguments is `::Zero`.
+Base.zero(::Type{Zero}) = Zero()
+
 ## We need to copy `x` as it will be used as might be given by the user and be
 ## given as first argument of `operate!!`.
 #Base.:(+)(zero::Zero, x) = copy_if_mutable(x)
diff --git a/test/rewrite.jl b/test/rewrite.jl
index 73216a88..e2d1c8ae 100644
--- a/test/rewrite.jl
+++ b/test/rewrite.jl
@@ -9,7 +9,7 @@ import MutableArithmetics as MA
 
 @testset "Zero" begin
     z = MA.Zero()
-    #@test zero(MA.Zero) isa MA.Zero
+    @test zero(MA.Zero) isa MA.Zero
     @test z + z isa MA.Zero
     @test z + 1 == 1
     @test 1 + z == 1