#16066: internal error: PAP object entered! ----------------------------------+---------------------------------------- Reporter: dnspies | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.4.4 Resolution: | Keywords: Operating System: iOS | Architecture: Unknown/Multiple Type of failure: Runtime crash | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ----------------------------------+---------------------------------------- Comment (by dnspies): I don't know about shrinking but I was able to isolate where it's happening. It's in the call to `STM`'s `return` method here: https://github.com/dspies- leapyear/persistwrap/blob/885a079923cb3eefb24db344f5e2fddee9fab425/persistwrap/src/PersistWrap/Persistable/Insert/Utils.hs#L130 I've added a `Monad2` typeclass and threaded it through the program in order to make it easy to play with the bug and get more info: https://github.com/dspies- leapyear/persistwrap/blob/e8ee02716acdd42ceea8210c9ef333c0f6c9d08d /persistwrap-table/src/PersistWrap/Table/Monad2.hs#L20 When I run {{{ stack test persistwrap:persistwrap-test --ta '-p "Widget.should get back"' }}} I get {{{ Progress 1/2: persistwrap-0.1.0.0test/Driver.hs widget Widget should get back what you put in: STM returning ValueSnd (V (PV 3)) persistwrap-test: internal error: PAP object entered! (GHC version 8.4.4 for x86_64_apple_darwin) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} So the message ''outside'' the return is getting printed but not the one on the inside. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16066#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler