LibJS: Add a PropertyName class that represents a string or a number

Now that we have two separate storages for Object properties depending
on what kind of index they have, it's nice to have an abstraction that
still allows us to say "here's a property name".

We use PropertyName to always choose the optimal storage path directly
while interpreting the AST. :^)

1 files changed, 7 insertions, 3 deletions

diff --git a/Libraries/LibJS/AST.cpp b/Libraries/LibJS/AST.cpp
index be00893918..e52f7f00ad 100644
--- a/Libraries/LibJS/AST.cpp
+++ b/Libraries/LibJS/AST.cpp
@@ -855,13 +855,17 @@ void MemberExpression::dump(int indent) const
     m_property->dump(indent + 1);
 }
 
-FlyString MemberExpression::computed_property_name(Interpreter& interpreter) const
+PropertyName MemberExpression::computed_property_name(Interpreter& interpreter) const
 {
     if (!is_computed()) {
         ASSERT(m_property->is_identifier());
-        return static_cast<const Identifier&>(*m_property).string();
+        return PropertyName(static_cast<const Identifier&>(*m_property).string());
     }
-    return m_property->execute(interpreter).to_string();
+    auto index = m_property->execute(interpreter);
+    // FIXME: What about non-integer numbers tho.
+    if (index.is_number())
+        return PropertyName(index.to_i32());
+    return PropertyName(index.to_string());
 }
 
 Value MemberExpression::execute(Interpreter& interpreter) const