One way to deal with this in GC languages is to have a separate read-only view on a mutable object. The example that comes to mind, though it's a bit more complex than a view on a simple data structure is CancellationToken (read only) vs CancellationTokenSource (writable in the sense of having "cancel()" method) in C#. I'm not saying it's better than proper mutability support but it does work well enough sometimes.