From bc78e4b7da2ccdad6e4368b90baa4830e64c4384 Mon Sep 17 00:00:00 2001
From: Linus Groh <mail@linusgroh.de>
Date: Wed, 7 Oct 2020 19:53:30 +0100
Subject: [PATCH] LibJS: Fix PropertyName::from_value() for negative and
 non-int numbers

It was converting *any* number to an i32 index, which obviously is not
correct for negative ints, doubles, infinity and nan.

Fixes #3712.
---
 Libraries/LibJS/Runtime/PropertyName.h               |  8 ++++----
 .../Tests/object-expression-computed-property.js     | 12 ++++++++++++
 2 files changed, 16 insertions(+), 4 deletions(-)
 create mode 100644 Libraries/LibJS/Tests/object-expression-computed-property.js

diff --git a/Libraries/LibJS/Runtime/PropertyName.h b/Libraries/LibJS/Runtime/PropertyName.h
index 4c74c9de9f..ab31b0fa4c 100644
--- a/Libraries/LibJS/Runtime/PropertyName.h
+++ b/Libraries/LibJS/Runtime/PropertyName.h
@@ -42,13 +42,13 @@ public:
 
     static PropertyName from_value(GlobalObject& global_object, Value value)
     {
+        if (value.is_empty())
+            return {};
         if (value.is_symbol())
             return &value.as_symbol();
-        if (value.is_number())
+        if (value.is_integer() && value.as_i32() >= 0)
             return value.as_i32();
-        if (!value.is_empty())
-            return value.to_string(global_object);
-        return {};
+        return value.to_string(global_object);
     }
 
     PropertyName() { }
diff --git a/Libraries/LibJS/Tests/object-expression-computed-property.js b/Libraries/LibJS/Tests/object-expression-computed-property.js
new file mode 100644
index 0000000000..7fa579d21e
--- /dev/null
+++ b/Libraries/LibJS/Tests/object-expression-computed-property.js
@@ -0,0 +1,12 @@
+test("Issue #3712, negative/non-int computed property in object expression", () => {
+    const o = {
+        [1.23]: "foo",
+        [-1]: "foo",
+        [NaN]: "foo",
+        [Infinity]: "foo",
+    };
+    expect(o[1.23]).toBe("foo");
+    expect(o[-1]).toBe("foo");
+    expect(o[NaN]).toBe("foo");
+    expect(o[Infinity]).toBe("foo");
+});