From f4129ac422a2ed7795d1b3f7a368277aed4b4754 Mon Sep 17 00:00:00 2001
From: Jack Karamanian <karamanian.jack@gmail.com>
Date: Sat, 30 May 2020 01:07:02 -0500
Subject: LibJS: Use the function's bound |this| and bound arguments in
 Interpreter::call()

---
 Libraries/LibJS/Interpreter.cpp                  |  5 +++--
 Libraries/LibJS/Tests/Function.prototype.bind.js | 11 +++++++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

(limited to 'Libraries')

diff --git a/Libraries/LibJS/Interpreter.cpp b/Libraries/LibJS/Interpreter.cpp
index 28b52900f6..d7b3a51fa5 100644
--- a/Libraries/LibJS/Interpreter.cpp
+++ b/Libraries/LibJS/Interpreter.cpp
@@ -207,9 +207,10 @@ Value Interpreter::call(Function& function, Value this_value, Optional<MarkedVal
 {
     auto& call_frame = push_call_frame();
     call_frame.function_name = function.name();
-    call_frame.this_value = this_value;
+    call_frame.this_value = function.bound_this().value_or(this_value);
+    call_frame.arguments = function.bound_arguments();
     if (arguments.has_value())
-        call_frame.arguments = arguments.value().values();
+        call_frame.arguments.append(arguments.value().values());
     call_frame.environment = function.create_environment();
     auto result = function.call(*this);
     pop_call_frame();
diff --git a/Libraries/LibJS/Tests/Function.prototype.bind.js b/Libraries/LibJS/Tests/Function.prototype.bind.js
index c6df364c15..34df409e21 100644
--- a/Libraries/LibJS/Tests/Function.prototype.bind.js
+++ b/Libraries/LibJS/Tests/Function.prototype.bind.js
@@ -11,6 +11,17 @@ try {
     }
     assert(getB.bind("bar")() === "B");
 
+    // Bound functions should work with array functions
+    var Make3 = Number.bind(null, 3);
+    assert([55].map(Make3)[0] === 3);
+
+    var MakeTrue = Boolean.bind(null, true);
+    assert([1, 2, 3].filter(MakeTrue).length === 3);
+
+    assert([1, 2, 3].reduce((function (acc, x) { return acc + x }).bind(null, 4, 5)) === 9);
+
+    assert([1, 2, 3].reduce((function (acc, x) { return acc + x + this; }).bind(3)) === 12);
+
     function sum(a, b, c) {
         return a + b + c;
     }
-- 
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