From 974bd7062b06b2d4c94a84b9c0210f7c89d47ef2 Mon Sep 17 00:00:00 2001
From: Michel Weststrate <mweststrate@fb.com>
Date: Thu, 21 May 2020 11:16:06 +0100
Subject: [PATCH] fix: Object.isFrozen dies on non objects in Internet
 Explorer. Fixes #600

---
 src/core/finalize.ts | 5 +++--
 src/utils/common.ts  | 8 +++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/core/finalize.ts b/src/core/finalize.ts
index f4ee8b77..200b264f 100644
--- a/src/core/finalize.ts
+++ b/src/core/finalize.ts
@@ -19,7 +19,8 @@ import {
 	ProxyTypeSet,
 	getPlugin,
 	die,
-	revokeScope
+	revokeScope,
+	isFrozen
 } from "../internal"
 
 export function processResult(result: any, scope: ImmerScope) {
@@ -59,7 +60,7 @@ export function processResult(result: any, scope: ImmerScope) {
 
 function finalize(rootScope: ImmerScope, value: any, path?: PatchPath) {
 	// Don't recurse in tho recursive data structures
-	if (Object.isFrozen(value)) return value
+	if (isFrozen(value)) return value
 
 	const state: ImmerState = value[DRAFT_STATE]
 	// A plain object, might need freezing, might contain drafts
diff --git a/src/utils/common.ts b/src/utils/common.ts
index 53a9fe74..fa1ea8a5 100644
--- a/src/utils/common.ts
+++ b/src/utils/common.ts
@@ -176,7 +176,7 @@ export function shallowCopy(base: any, invokeGetters = false) {
 }
 
 export function freeze(obj: any, deep: boolean): void {
-	if (isDraft(obj) || Object.isFrozen(obj) || !isDraftable(obj)) return
+	if (isDraft(obj) || isFrozen(obj) || !isDraftable(obj)) return
 	if (getArchtype(obj) > 1 /* Map or Set */) {
 		obj.set = obj.add = obj.clear = obj.delete = dontMutateFrozenCollections as any
 	}
@@ -187,3 +187,9 @@ export function freeze(obj: any, deep: boolean): void {
 function dontMutateFrozenCollections() {
 	die(2)
 }
+
+export function isFrozen(obj: any): boolean {
+	if (obj == null || typeof obj !== "object") return true
+	// See #600, IE dies on non-objects in Object.isFrozen
+	return Object.isFrozen(obj)
+}