From b184ae81af8a26be68363b3905cfc4d74411f9c1 Mon Sep 17 00:00:00 2001
From: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>
Date: Sat, 12 Jan 2019 16:46:40 +0100
Subject: [PATCH] Make sure object prototype methods are not considered to be
 falsy

---
 src/ast/nodes/ObjectExpression.ts                   | 13 +++++++------
 .../builtin-prototypes/truthiness/_config.js        |  3 +++
 .../samples/builtin-prototypes/truthiness/main.js   |  5 +++++
 3 files changed, 15 insertions(+), 6 deletions(-)
 create mode 100644 test/function/samples/builtin-prototypes/truthiness/_config.js
 create mode 100644 test/function/samples/builtin-prototypes/truthiness/main.js

diff --git a/src/ast/nodes/ObjectExpression.ts b/src/ast/nodes/ObjectExpression.ts
index aa3c73e5d85..2f6d7ff06e1 100644
--- a/src/ast/nodes/ObjectExpression.ts
+++ b/src/ast/nodes/ObjectExpression.ts
@@ -78,6 +78,7 @@ export default class ObjectExpression extends NodeBase {
 		if (
 			path.length === 1 &&
 			!this.propertyMap[key] &&
+			!objectMembers[key] &&
 			this.unmatchablePropertiesRead.length === 0
 		) {
 			if (!this.expressionsToBeDeoptimized[key]) {
@@ -167,8 +168,8 @@ export default class ObjectExpression extends NodeBase {
 		for (const property of typeof key !== 'string'
 			? this.properties
 			: this.propertyMap[key]
-				? this.propertyMap[key].propertiesRead
-				: []) {
+			? this.propertyMap[key].propertiesRead
+			: []) {
 			if (property.hasEffectsWhenAccessedAtPath(subPath, options)) return true;
 		}
 		return false;
@@ -191,10 +192,10 @@ export default class ObjectExpression extends NodeBase {
 		for (const property of typeof key !== 'string'
 			? this.properties
 			: path.length > 1
-				? this.propertyMap[key].propertiesRead
-				: this.propertyMap[key]
-					? this.propertyMap[key].propertiesSet
-					: []) {
+			? this.propertyMap[key].propertiesRead
+			: this.propertyMap[key]
+			? this.propertyMap[key].propertiesSet
+			: []) {
 			if (property.hasEffectsWhenAssignedAtPath(subPath, options)) return true;
 		}
 		return false;
diff --git a/test/function/samples/builtin-prototypes/truthiness/_config.js b/test/function/samples/builtin-prototypes/truthiness/_config.js
new file mode 100644
index 00000000000..9c57e067add
--- /dev/null
+++ b/test/function/samples/builtin-prototypes/truthiness/_config.js
@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'regards builtin methods as truthy in objects'
+};
diff --git a/test/function/samples/builtin-prototypes/truthiness/main.js b/test/function/samples/builtin-prototypes/truthiness/main.js
new file mode 100644
index 00000000000..f24b8952032
--- /dev/null
+++ b/test/function/samples/builtin-prototypes/truthiness/main.js
@@ -0,0 +1,5 @@
+if (!{}.hasOwnProperty) {
+	throw new Error('Prototype method evaluated as falsy');
+}
+
+assert.strictEqual({}.hasOwnProperty ? true : false, true);