#14777: panic when using a function defined in terms of `error` -------------------------------------+------------------------------------- Reporter: zilinc | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Compile-time | Unknown/Multiple crash or panic | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by dfeuer): I took a peek at monoidal's reproduction, using a devel2 build of 8.2.2 with some extra `HasCallStack`s. Running with Core Lint and `-O2`, I get {{{ [2 of 2] Compiling Cogent.Desugar ( Cogent/Desugar.hs, Cogent/Desugar.o ) WARNING: file compiler/simplCore/OccurAnal.hs, line 69 Glomming in Cogent.Desugar: [s55P :-> OnceL!] ghc-stage2: panic! (the 'impossible' happened) (GHC version 8.2.2 for x86_64-unknown-linux): idInfo v_X5mQ 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/basicTypes/Var.hs:526:34 in ghc:Var idInfo, called at compiler/basicTypes/Id.hs:736:37 in ghc:Id idInlinePragma, called at compiler/basicTypes/Id.hs:745:49 in ghc:Id idInlineActivation, called at compiler/simplCore/SimplUtils.hs:923:56 in ghc:SimplUtils getUnfoldingInRuleMatch, called at compiler/simplCore/Simplify.hs:1946:34 in ghc:Simplify tryRules, called at compiler/simplCore/Simplify.hs:1776:22 in ghc:Simplify }}} (I have no idea if the lint warning is relevant). About all I can see about what's gone wrong is that something seems to be treating a type variable as though it were a term variable. That is, if I understand the `Var` type properly. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14777#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler