#15745: Panicking typechecker plugins -------------------------------------+------------------------------------- Reporter: philderbeast | Owner: (none) Type: feature | Status: new request | Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 (Type checker) | 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: -------------------------------------+------------------------------------- If I use a typechecker plugin that fails then ghc panics and I'm asked to report a bug with GHC; {{{ ghc: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-apple-darwin): Prelude.undefined CallStack (from HasCallStack): error, called at libraries/base/GHC/Err.hs:79:14 in base:GHC.Err undefined, called at plugin/Undefined/Solve/Plugin.hs:14:39 in undefined-solve- plugin-1.0.0.0-56evBabJYBHHTUlrE3HO5m:Undefined.Solve.Plugin Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug }}} Could we please say that it is the typechecker plugin that is panicking and ask for a bug report for the faulty typechecker, giving the issues URL for the plugin if we know it? The following [https://github.com/BlockScope/undefined-plugin undefined plugins] fail for init, solve and stop functions. {{{ #!haskell module Undefined.Init.Plugin (plugin) where import Plugins (Plugin(..), tcPlugin, defaultPlugin) import TcRnTypes (TcPluginM, TcPluginResult(..), Ct, TcPlugin(..)) import GHC.TcPluginM.Extra (tracePlugin) plugin :: Plugin plugin = defaultPlugin { tcPlugin = const $ Just undefinedPlugin } undefinedPlugin :: TcPlugin undefinedPlugin = tracePlugin "undefined-init-plugin" $ TcPlugin { tcPluginInit = undefined , tcPluginSolve = \_ _ _ _ -> return $ TcPluginOk [] [] , tcPluginStop = const $ return () } }}} {{{ #!haskell module Undefined.Solve.Plugin (plugin) where import Plugins (Plugin(..), tcPlugin, defaultPlugin) import TcRnTypes (TcPluginM, TcPluginResult, Ct, TcPlugin(..)) import GHC.TcPluginM.Extra (tracePlugin) plugin :: Plugin plugin = defaultPlugin { tcPlugin = const $ Just undefinedPlugin } undefinedPlugin :: TcPlugin undefinedPlugin = tracePlugin "undefined-solve-plugin" $ TcPlugin { tcPluginInit = return () , tcPluginSolve = \_ _ _ _ -> undefined , tcPluginStop = const $ return () } }}} {{{ #!haskell module Undefined.Stop.Plugin (plugin) where import Plugins (Plugin(..), tcPlugin, defaultPlugin) import TcRnTypes (TcPluginM, TcPluginResult(..), Ct, TcPlugin(..)) import GHC.TcPluginM.Extra (tracePlugin) plugin :: Plugin plugin = defaultPlugin { tcPlugin = const $ Just undefinedPlugin } undefinedPlugin :: TcPlugin undefinedPlugin = tracePlugin "undefined-stop-plugin" $ TcPlugin { tcPluginInit = return () , tcPluginSolve = \_ _ _ _ -> return $ TcPluginOk [] [] , tcPluginStop = const $ undefined } }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15745 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler