Looking at your Pager type and the code, that’s pretty straightforward and would seem to be covered by the existing unit tests. Is that still representative of you code that is failing? I will try to construct a program with those snippets to see if I can repro the problem.
There was a change to support polymorphic types and it’s always possible that I broke something, but my unit tests (which include basic types, complex types, arrays, and polymorphic classes) did pass. If you have an instance factory, the signature changed.
This crash isn’t ringing any bells with me, but I will run some tests and see if I can reproduce the problem using your fn’s and Pager type.