#16135: Panic with ExistentialQuantification and ApplicativeDo -------------------------------------+------------------------------------- Reporter: Ashley Yakeley | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.6.3 Resolution: | 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: | -------------------------------------+------------------------------------- Description changed by Ashley Yakeley: Old description:
{{{ {-# LANGUAGE ExistentialQuantification, ApplicativeDo #-}
module Bug where
data T f = forall a. MkT (f a)
runf :: forall f. Functor f => IO (T f) runf = do return () MkT fa <- runf return $ MkT fa }}}
{{{
Bug.hs:11:18: error:ghc: panic! (the 'impossible' happened) (GHC version 8.6.3 for x86_64-unknown-linux): No skolem info: [a_a1nb[ssk:2]] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/typecheck/TcErrors.hs:2891:5 in ghc:TcErrors
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}}
New description: {{{#!hs {-# LANGUAGE ExistentialQuantification, ApplicativeDo #-} module Bug where data T f = forall a. MkT (f a) runf :: forall f. Functor f => IO (T f) runf = do return () MkT fa <- runf return $ MkT fa }}} {{{ Bug.hs:11:18: error:ghc: panic! (the 'impossible' happened) (GHC version 8.6.3 for x86_64-unknown-linux): No skolem info: [a_a1nb[ssk:2]] Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1160:37 in ghc:Outputable pprPanic, called at compiler/typecheck/TcErrors.hs:2891:5 in ghc:TcErrors Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16135#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler