yanhasu

Adding `seed :: [a]` *does* make the error go away for me, provided that I also: * Add `{-# LANGUAGE ScopedTypeVariables #-}` at the top of the file * Add...

I also noticed that you don't even need to use abstract refinements to get the bug. i.e. if I remove all references to `UList` and just use plain `[a]`, [the...

I suspect that the bug comes from the built-in refinement of `[a]`. If I port [`Blank3`](http://goto.ucsd.edu:8090/index.html#?demo=permalink%2F1626354457_37152.hs) to a custom list type (which doesn't bind an abstract refinement), [the bug goes...