#13991: I was building/testing a haskell project using stack ..suddenly I see the following output. Also attached the project -------------------------------------+------------------------------------- Reporter: chandrakoduru | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- putting-haskell-to-test-0.0.1.0: build (lib + test) Preprocessing library putting-haskell-to-test-0.0.1.0... Preprocessing test suite 'HUnitTest' for putting-haskell-to- test-0.0.1.0... [1 of 1] Compiling Main ( test/HUnitTest/Spec.hs, .stack- work/dist/x86_64-linux/Cabal-1.24.2.0/build/HUnitTest/HUnitTest-tmp/Main.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): initTc: unsolved constraints WC {wc_insol = [W] @?=_a1lM :: t_a1lL[tau:1] (CHoleCan: @?=) [W] testCase_a1m2 :: t_a1m1[tau:1] (CHoleCan: testCase) [W] simpleMathFunction_a1mb :: t_a1ma[tau:1] (CHoleCan: simpleMathFunction) [W] @?=_a1xp :: t_a1xo[tau:1] (CHoleCan: @?=) [W] testCase_a1xB :: t_a1xA[tau:1] (CHoleCan: testCase) [W] simpleMathFunction_a1xK :: t_a1xJ[tau:1] (CHoleCan: simpleMathFunction)} Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug Progress: 1/2 -- While building package putting-haskell-to-test-0.0.1.0 using: /home/local/ANT/chandrak/.stack/setup-exe-cache/x86_64-linux/Cabal- simple_mPHDZzAJ_1.24.2.0_ghc-8.0.2 --builddir=.stack- work/dist/x86_64-linux/Cabal-1.24.2.0 build lib:putting-haskell-to-test test:HUnitTest --ghc-options " -ddump-hi -ddump-to-file" Process exited with code: ExitFailure 1 -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13991 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler