Create function-newproxy-table-support

rfcs/function-newproxy-table-support

@@ -0,0 +1,25 @@
+# Support table as first argument to newproxy
+
+## Summary
+
+Introduce a new way of creating `userdata` objects from Luau with an existing metatable.
+
+## Motivation
+
+Since Luau is derived from Lua 5.1 it retains the `newproxy` function used to create custom `userdata` objects from Lua. While this function is used by a number of libraries it has its limitations.
+
+The `newproxy` function accepts a single, boolean parameter which specifies if the newly created `userdata` should be initialized with a metatable or not. If the `userdata` is initialized with a metatable then it can be retrieved and edited by calling `getmetatable`. Unfortunately, this means that a `userdata` created through `newproxy` cannot share a metatable with another `userdata`. There are two main implications of this:
+- Memory - A `userdata` with a metatable has the same cost as a table with a metatable.
+- Usability - `userdata` with the same 'type' do not have the same metatable.
+
+## Design
+
+TODO
+
+## Drawbacks
+
+TODO: It will increase the usage of newproxy which may not be desirable.
+
+## Alternatives
+
+TODO: New method entirely - add more support for userdata