#13803: Panic while forcing the thunk for TyThing IsFile (regression) -------------------------------------+------------------------------------- Reporter: inaki | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- (Apologies in advance for the very non-minimal testcase. I have been unsuccessfully trying to reduce the testcase for a few hours now, but I am flying blind, and the bug seems to depend on the interaction of various modules. The panic is very reproducible for me, so I figured that better reporting even if I failed to obtain a simplified testcase. Maybe someone else has more luck isolating the issue.) When compiling `gi-gio-2.0.12` I consistently get the following GHC panic: {{{ [259 of 293] Compiling GI.Gio.Interfaces.File ( GI/Gio/Interfaces/File.hs, dist/build/GI/Gio/Interfaces/File.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.2.0.20170507 for x86_64-unknown-linux): tcIfaceGlobal (local): not found You are in a maze of twisty little passages, all alike. While forcing the thunk for TyThing IsFile which was lazily initialized by initIfaceCheck typecheckLoop, I tried to tie the knot, but I couldn't find IsFile in the current type environment. If you are developing GHC, please read Note [Tying the knot] and Note [Type-checking inside the knot]. Consider rebuilding GHC with profiling for a better stack trace. Contents of current type environment: [] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1134:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1138:37 in ghc:Outputable pprPanic, called at compiler/iface/TcIface.hs:1689:23 in ghc:TcIface Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} To compile this code you will need the `glib2-devel` package installed. To compile {{{ $ cabal get gi-gio-2.0.12 $ cd gi-gio-2.0.12 $ cabal sandbox init $ cabal install --dependencies-only $ cabal build }}} I am running version `8.2.0.20170507`, from https://copr.fedorainfracloud.org/coprs/petersen/ghc-8.2.1/ . The same code compiles in versions `7.8.x`, `7.10.x` and `8.0.x`. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13803 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler