#13819: GHC Panics -------------------------------------+------------------------------------- Reporter: Iceland_jack | 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: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE DeriveFunctor, TypeApplications #-} -- {-# Language ViewPatterns #-} -- {-# Language InstanceSigs, ViewPatterns, TupleSections, GeneralizedNewtypeDeriving, TemplateHaskell, LambdaCase #-} module D where import Data.Coerce import Control.Applicative newtype A a = A (IO a) deriving Functor instance Applicative A where pure = pure @(_ -> WrappedMonad A _) @(_ -> A _) pure instance Monad A where }}} causes a panic {{{ $ ghci -ignore-dot-ghci /tmp/a.hs GHCi, version 8.3.20170605: http://www.haskell.org/ghc/ :? for help [1 of 1] Compiling D ( /tmp/a.hs, interpreted ) ghc: panic! (the 'impossible' happened) (GHC version 8.3.20170605 for x86_64-unknown-linux): repSplitAppTys w0_a1xc[tau:4] WrappedMonad A w0_a1xe[tau:4] [] Call stack: CallStack (from HasCallStack): prettyCurrentCallStack, called at compiler/utils/Outputable.hs:1133:58 in ghc:Outputable callStackDoc, called at compiler/utils/Outputable.hs:1137:37 in ghc:Outputable pprPanic, called at compiler/types/Type.hs:809:9 in ghc:Type Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
}}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13819 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler