#12957: In a record-update construct:ghc-stage2: panic! (the 'impossible' happened) -------------------------------------+------------------------------------- Reporter: niteria | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by RyanGlScott): I think it very well might be the same bug, considering the form of the panic is identical to how niteria originally reported it: {{{ $ ghci -fdefer-type-errors Bug.hsGHCi, version 8.0.2: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Main ( Bug.hs, interpreted ) Bug.hs:3:16: warning: [-Woverlapping-patterns] Pattern match is redundant In a case alternative: (_ : _) -> ... Bug.hs:3:25: warning: [-Wdeferred-out-of-scope-variables] Variable not in scope: a :: A Bug.hs:3:25: warning: [-Woverlapping-patterns] Pattern match is redundant In a record-update construct:ghc: panic! (the 'impossible' happened) (GHC version 8.0.2 for x86_64-unknown-linux): unused }}} Also reproducible on GHC HEAD. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12957#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler