#13106: impossible happened: initTc: unsolved constraints -------------------------------------+------------------------------------- Reporter: codygman | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 Resolution: | Keywords: initTc Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #12921 | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by Simon Peyton Jones <simonpj@…>): In [changeset:"f5f6d4237b87f5d0e3e0a05e4cfc52bb3c0e4ad9/ghc" f5f6d423/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="f5f6d4237b87f5d0e3e0a05e4cfc52bb3c0e4ad9" Fix top-level constraint handling (Trac #12921) Some out-of-scope errors were not being reported if anyone throws an un-caught exception in the TcM monad. That led to ghc: panic! (the 'impossible' happened) initTc: unsolved constraints I fixed this * Splitting captureConstraints to use an auxilliary tryCaptureConstraints (which never fails) * Define a new TcSimplify.captureTopConstraints (replacing the old TcRnMonad.captureTopConstraints), which reports any unsolved out-of-scope constraints before propagating the exception That in turn allowed me to do some tidying up of the static-constraint machinery, reducing duplication. Also solves #13106. }}} -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13106#comment:5> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler