Attached. Your output seems to have additional messages that are enabled when `debugIsOn`, so maybe some other debugging output or assertion is
#10533: Typechecker behaves differently on Phab and on Mac -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.11 Resolution: | Keywords: Operating System: MacOS X | Architecture: Type of failure: None/Unknown | Unknown/Multiple Blocked By: | Test Case: Related Tickets: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- Comment (by goldfire): Replying to [comment:5 rwbarton]: panicking for you? Of course. The panic is an `ASSERT`ion failure. So perhaps the problem is happening on all platforms, but only caught in a `DEBUG` build. Indeed, your log contains the problematic derived constraint at the end of `tryReporters`. It just doesn't bail out. So, weirdness resolved, I believe... but now we need to figure out why that assertion is failing. Modifying ticket accordingly. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10533#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler