This is worrying, but then again, :print has been known to trigger this isUnliftedType panic in other ways for some time now (see #14828). In
#11514: Impredicativity is still sneaking in -------------------------------------+------------------------------------- Reporter: goldfire | Owner: goldfire Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Resolution: | Keywords: | ImpredicativeTypes Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): light of this, I'm not sure if it's worth investing the effort to fix this :print panic, or just accept this as a known regression. Yes it looks exactly like #14828. I'd be inlined to accept the regression. But it would be great if someone was to actually look at #14828. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11514#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler