Because defining a global function or a local variable usually involves introduction of a new name we didn’t intend to provide autocomplete suggestions in these cases.
While it’s true that it might be a method definition on a table in the scope, we don’t know that until we get to ‘.’ or ‘:’.
In essence, we don’t have a code with a bug for this situation, we don’t have any code at all.
Having said that, for Luau we try to discourage definitions of global functions, so we do have an opportunity to treat ‘function ___’ as a beginning of a method and suggest tables available in scope.