From ef47fa26f550b904d1f5515d74219434205708ab Mon Sep 17 00:00:00 2001
From: Matt Phillips <matt@mattphillips.io>
Date: Wed, 20 Mar 2019 10:00:33 +0000
Subject: [PATCH] Add circular shape checking

---
 packages/expect/src/__tests__/utils.test.js | 11 +++++++++++
 packages/expect/src/utils.ts                |  2 --
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/packages/expect/src/__tests__/utils.test.js b/packages/expect/src/__tests__/utils.test.js
index b91634157858..7ff609a8ab87 100644
--- a/packages/expect/src/__tests__/utils.test.js
+++ b/packages/expect/src/__tests__/utils.test.js
@@ -241,6 +241,17 @@ describe('iterableEquality', () => {
     ).toBe(false);
   });
 
+  test('returns true when given circular Set shape', () => {
+    const a1 = new Set();
+    const a2 = new Set();
+    a1.add(a2);
+    a2.add(a1);
+    const b = new Set();
+    b.add(b);
+
+    expect(iterableEquality(a1, b)).toBe(true);
+  });
+
   test('returns true when given circular key in Map', () => {
     const a = new Map();
     a.set(a, 'a');
diff --git a/packages/expect/src/utils.ts b/packages/expect/src/utils.ts
index 245f227701cf..749b20ec597d 100644
--- a/packages/expect/src/utils.ts
+++ b/packages/expect/src/utils.ts
@@ -166,8 +166,6 @@ export const iterableEquality = (
     // circular reference is not equal to non-circular one
     if (aStack[length] === a) {
       return bStack[length] === b;
-    } else if (bStack[length] === b) {
-      return false;
     }
   }
   aStack.push(a);