:: String -> Int -package:hledger-lib -package:speculate -package:express -package:monads-tf -package:ghc-lib-parser -package:dbus is:exact package:polysemy

The error used in fixpointToFinal, runFixpoint and runFixpointM when the result of a failed computation is recursively used and somehow visible. You may use this for your own Fixpoint interpreters. The argument should be the name of the interpreter.