From da0ab16f011bec0c4da862db80dc53c2122e04f2 Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Tue, 28 Apr 2020 23:58:23 +0100
Subject: [PATCH] LibJS: Don't handle arrays separately in Value::to_number()

Now that Array.prototype.join() is producing the correct results we
can remove the separate code path for arrays in Value::to_number()
and treat them like all other objects - using to_primitive() with
number as the preferred type and then calling to_number() on the
result.

This is how the spec descibes it.

This also means we don't crash anymore when trying to coerce
[<empty>] to a number - it now does the following:

[<empty>] - to string - "" - to number - 0
[<empty>, <empty>] - to string - "," - to number - NaN
---
 Libraries/LibJS/Runtime/Value.cpp        | 11 +----------
 Libraries/LibJS/Tests/to-number-basic.js | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/Libraries/LibJS/Runtime/Value.cpp b/Libraries/LibJS/Runtime/Value.cpp
index e2457d5ce4..d0998e4ec1 100644
--- a/Libraries/LibJS/Runtime/Value.cpp
+++ b/Libraries/LibJS/Runtime/Value.cpp
@@ -162,16 +162,7 @@ Value Value::to_number() const
     case Type::Undefined:
         return js_nan();
     case Type::Object:
-        if (m_value.as_object->is_array()) {
-            auto& array = *static_cast<Array*>(m_value.as_object);
-            if (array.length() == 0)
-                return Value(0);
-            if (array.length() > 1)
-                return js_nan();
-            return array.elements()[0].to_number();
-        } else {
-            return m_value.as_object->to_primitive(Object::PreferredType::Number).to_number();
-        }
+        return m_value.as_object->to_primitive(Object::PreferredType::Number).to_number();
     }
 
     ASSERT_NOT_REACHED();
diff --git a/Libraries/LibJS/Tests/to-number-basic.js b/Libraries/LibJS/Tests/to-number-basic.js
index e0d07a51fe..902ad293f2 100644
--- a/Libraries/LibJS/Tests/to-number-basic.js
+++ b/Libraries/LibJS/Tests/to-number-basic.js
@@ -9,6 +9,12 @@ try {
     assert(-null === 0);
     assert(+[] === 0);
     assert(-[] === 0);
+    assert(+[,] === 0);
+    assert(-[,] === 0);
+    assert(+[null] === 0);
+    assert(-[null] === 0);
+    assert(+[undefined] === 0);
+    assert(-[undefined] === 0);
     assert(+[[[[[]]]]] === 0);
     assert(-[[[[[]]]]] === 0);
     assert(+[[[[[42]]]]] === 42);
@@ -35,8 +41,12 @@ try {
     assert(isNaN(-undefined));
     assert(isNaN(+{}));
     assert(isNaN(-{}));
-    assert(isNaN(+{a: 1}));
-    assert(isNaN(-{a: 1}));
+    assert(isNaN(+{ a: 1 }));
+    assert(isNaN(-{ a: 1 }));
+    assert(isNaN(+[, , ,]));
+    assert(isNaN(-[, , ,]));
+    assert(isNaN(+[undefined, undefined]));
+    assert(isNaN(-[undefined, undefined]));
     assert(isNaN(+[1, 2, 3]));
     assert(isNaN(-[1, 2, 3]));
     assert(isNaN(+[[[["foo"]]]]));