#14051: Unboxed sums-related panic: getUnboxedSumName 513 -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1-rc2 Keywords: UnboxedSums | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- Originally reported [https://www.reddit.com/r/haskell/comments/6q6yau/unboxed_sums_ghc_panic/ here]. You'll need these two files: {{{#!hs -- Testing.hs {-# LANGUAGE UnboxedSums #-} module Testing where func :: s -> (# Bool | Bool #) func _ = (# True | #) }}} {{{#!hs -- Bug.hs {-# LANGUAGE UnboxedSums #-} module Main where import Testing main :: IO () main = print $ func 1 }}} And you must compile them like so (the `-c` and `-O2` flags are important): {{{ $ ghc -O2 -c Testing.hs $ ghc -O2 -c Bug.hs ghc: panic! (the 'impossible' happened) (GHC version 8.2.1 for x86_64-unknown-linux): getUnboxedSumName 513 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/prelude/KnownUniques.hs:104:5 in ghc:KnownUniques }}} Reproducible with GHC 8.2.1 and HEAD. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14051 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler