From d3ace4be5663548799db9ef723861bf8a2ef487d Mon Sep 17 00:00:00 2001
From: Andy Dienes <andydienes@gmail.com>
Date: Tue, 1 Jul 2025 10:33:44 -0400
Subject: [PATCH 1/3] fix == and show on self-referential arrays

---
 base/abstractarray.jl |  3 +++
 base/arrayshow.jl     | 12 ++++++++----
 test/abstractarray.jl | 17 +++++++++++++++++
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index 94bf3170feb38..f1668d6f467a1 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -3029,6 +3029,9 @@ Return `true` when `A` is less than `B` in lexicographic order.
 isless(A::AbstractVector, B::AbstractVector) = cmp(A, B) < 0
 
 function (==)(A::AbstractArray, B::AbstractArray)
+    if A === B
+        return true
+    end
     if axes(A) != axes(B)
         return false
     end
diff --git a/base/arrayshow.jl b/base/arrayshow.jl
index f792d26d8e9b5..554832bdc47de 100644
--- a/base/arrayshow.jl
+++ b/base/arrayshow.jl
@@ -442,7 +442,9 @@ function _show_nonempty(io::IO, @nospecialize(X::AbstractMatrix), prefix::String
                         print(io, undef_ref_str)
                     else
                         el = X[i,j]
-                        show(io, el)
+                        if !show_circular(io, el)
+                            show(io, el)
+                        end
                     end
                 end
                 if last(cr) == last(indc)
@@ -488,9 +490,11 @@ function show(io::IO, X::AbstractArray)
     if !implicit
         io = IOContext(io, :typeinfo => eltype(X))
     end
-    isempty(X) ?
-        _show_empty(io, X) :
-        _show_nonempty(io, X, prefix)
+    if isempty(X)
+        return _show_empty(io, X)
+    end
+    recur_io = IOContext(io, :SHOWN_SET => X)
+    _show_nonempty(recur_io, X, prefix)
 end
 
 ### 0-dimensional arrays (#31481)
diff --git a/test/abstractarray.jl b/test/abstractarray.jl
index ad821855e573a..68390057643f9 100644
--- a/test/abstractarray.jl
+++ b/test/abstractarray.jl
@@ -2310,3 +2310,20 @@ end
     v2 = view(A, Base.IdentityUnitRange(1:length(A)))
     @test sum(x for x in v2) == sum(A)
 end
+
+@testset "self referential" begin
+    v = Any[1,2,3]
+    m = Any[1 2 3]
+
+    v[1] = v
+    m[1] = m
+
+    @test v == v == v[1]
+    @test m == m == m[1]
+
+    io = IOBuffer()
+    show(io, v)
+    @test String(take!(io)) == "Any[Any[#= circular reference @-1 =#], 2, 3]"
+    show(io, m)
+    @test String(take!(io)) == "Any[#= circular reference @-1 =# 2 3]"
+end

From a857150236d5923ae654f3dcba226889334ba81c Mon Sep 17 00:00:00 2001
From: Andy Dienes <andydienes@gmail.com>
Date: Tue, 1 Jul 2025 13:16:54 -0400
Subject: [PATCH 2/3] punt on equality changes

---
 base/abstractarray.jl | 3 ---
 test/abstractarray.jl | 5 +++--
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index f1668d6f467a1..94bf3170feb38 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -3029,9 +3029,6 @@ Return `true` when `A` is less than `B` in lexicographic order.
 isless(A::AbstractVector, B::AbstractVector) = cmp(A, B) < 0
 
 function (==)(A::AbstractArray, B::AbstractArray)
-    if A === B
-        return true
-    end
     if axes(A) != axes(B)
         return false
     end
diff --git a/test/abstractarray.jl b/test/abstractarray.jl
index 68390057643f9..3af8df45de28b 100644
--- a/test/abstractarray.jl
+++ b/test/abstractarray.jl
@@ -2318,8 +2318,9 @@ end
     v[1] = v
     m[1] = m
 
-    @test v == v == v[1]
-    @test m == m == m[1]
+    # TODO: unclear how this (and `hash`) can work without tracking the objectid of each element
+    @test_broken (v == v == v[1])
+    @test_broken (m == m == m[1])
 
     io = IOBuffer()
     show(io, v)

From 7f92f5f34138222b6c4147b0830f37fed434fb19 Mon Sep 17 00:00:00 2001
From: Andy Dienes <andydienes@gmail.com>
Date: Tue, 8 Jul 2025 09:21:42 -0400
Subject: [PATCH 3/3] remove test_brokens

---
 test/abstractarray.jl | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/test/abstractarray.jl b/test/abstractarray.jl
index 3af8df45de28b..f4528ad12d4b6 100644
--- a/test/abstractarray.jl
+++ b/test/abstractarray.jl
@@ -2318,10 +2318,6 @@ end
     v[1] = v
     m[1] = m
 
-    # TODO: unclear how this (and `hash`) can work without tracking the objectid of each element
-    @test_broken (v == v == v[1])
-    @test_broken (m == m == m[1])
-
     io = IOBuffer()
     show(io, v)
     @test String(take!(io)) == "Any[Any[#= circular reference @-1 =#], 2, 3]"