From 45ccd9f8d9dae34120d3001f1885f2b521b7bba9 Mon Sep 17 00:00:00 2001
From: Jack Karamanian <karamanian.jack@gmail.com>
Date: Sat, 30 May 2020 00:13:42 -0500
Subject: [PATCH] LibJS: Set the bound |this| value to the |this| value of the
 current scope for arrow functions

---
 Libraries/LibJS/Runtime/ScriptFunction.cpp       |  2 +-
 Libraries/LibJS/Tests/Function.prototype.bind.js |  5 ++---
 Libraries/LibJS/Tests/arrow-functions.js         | 13 +++++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/Libraries/LibJS/Runtime/ScriptFunction.cpp b/Libraries/LibJS/Runtime/ScriptFunction.cpp
index b5b857f620..5d0857823f 100644
--- a/Libraries/LibJS/Runtime/ScriptFunction.cpp
+++ b/Libraries/LibJS/Runtime/ScriptFunction.cpp
@@ -53,7 +53,7 @@ ScriptFunction* ScriptFunction::create(GlobalObject& global_object, const FlyStr
 }
 
 ScriptFunction::ScriptFunction(const FlyString& name, const Statement& body, Vector<FunctionNode::Parameter> parameters, i32 m_function_length, LexicalEnvironment* parent_environment, Object& prototype, bool is_arrow_function)
-    : Function(prototype)
+    : Function(prototype, is_arrow_function ? interpreter().this_value() : Value(), {})
     , m_name(name)
     , m_body(body)
     , m_parameters(move(parameters))
diff --git a/Libraries/LibJS/Tests/Function.prototype.bind.js b/Libraries/LibJS/Tests/Function.prototype.bind.js
index 77d5a76faf..c6df364c15 100644
--- a/Libraries/LibJS/Tests/Function.prototype.bind.js
+++ b/Libraries/LibJS/Tests/Function.prototype.bind.js
@@ -102,9 +102,8 @@ try {
     //     assert(strictIdentity.bind(undefined)() === undefined);
     // })();
 
-    // FIXME: Uncomment me when arrow functions have the correct |this| value.
-    // // Arrow functions can not have their |this| value set.
-    // assert((() => this).bind("foo")() === globalThis)
+    // Arrow functions can not have their |this| value set.
+    assert((() => this).bind("foo")() === globalThis)
 
     console.log("PASS");
 } catch (e) {
diff --git a/Libraries/LibJS/Tests/arrow-functions.js b/Libraries/LibJS/Tests/arrow-functions.js
index ba2cb5cb0b..d34a7836f2 100644
--- a/Libraries/LibJS/Tests/arrow-functions.js
+++ b/Libraries/LibJS/Tests/arrow-functions.js
@@ -64,6 +64,19 @@ try {
     assert(foo === undefined);
     assert(bar === undefined);
 
+    function FooBar() {
+      this.x = {
+        y: () => this,
+        z: function () {
+          return (() => this)();
+        }
+      };
+    }
+
+    var foobar = new FooBar();
+    assert(foobar.x.y() === foobar);
+    assert(foobar.x.z() === foobar.x);
+
     (() => {
         "use strict";
         assert(isStrictMode());