From a9779ff61b260fab559f5af1d0f89a81ffd0cb70 Mon Sep 17 00:00:00 2001
From: Herman Sletmoen <hermansletmoen@gmail.com>
Date: Sun, 24 Mar 2024 22:38:12 +0100
Subject: [PATCH] Promote div and / in the same way (#270)

---
 src/interface.jl  | 8 ++++----
 test/interface.jl | 9 +++++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/interface.jl b/src/interface.jl
index e7c95c5b..74f94903 100644
--- a/src/interface.jl
+++ b/src/interface.jl
@@ -33,16 +33,16 @@ _instantiate(::Type{S}) where {S<:Irrational} = S()
 _instantiate_zero(::Type{S}) where {S<:AbstractIrrational} = _instantiate(S)
 _instantiate_oneunit(::Type{S}) where {S<:AbstractIrrational} = _instantiate(S)
 
+# Julia v1.0.x has trouble with inference with the `Vararg` method, see
+# https://travis-ci.org/jump-dev/JuMP.jl/jobs/617606373
 function promote_operation_fallback(
-    ::typeof(/),
+    op::Union{typeof(/),typeof(div)},
     ::Type{S},
     ::Type{T},
 ) where {S,T}
-    return typeof(_instantiate_zero(S) / _instantiate_oneunit(T))
+    return typeof(op(_instantiate_zero(S), _instantiate_oneunit(T)))
 end
 
-# Julia v1.0.x has trouble with inference with the `Vararg` method, see
-# https://travis-ci.org/jump-dev/JuMP.jl/jobs/617606373
 function promote_operation_fallback(
     op::F,
     ::Type{S},
diff --git a/test/interface.jl b/test/interface.jl
index 489a567d..aed08ecd 100644
--- a/test/interface.jl
+++ b/test/interface.jl
@@ -178,3 +178,12 @@ end
     @test MA.operate_to!!(T(6), abs, T(7)) == 7
     @test MA.operate_to!!(T(6), abs, T(-7)) == 7
 end
+
+@testset "Error-free mutability (issue #240)" begin
+    for op in (+, -, *, /, div)
+        for T in
+            (Float64, BigFloat, Int, BigInt, Rational{Int}, Rational{BigInt})
+            @test_nowarn MA.mutability(T, op, T, T) # should run without error
+        end
+    end
+end