#7142 closed bug (duplicate)

ghc: panic! (the 'impossible' happened) when using lowercase eq/show in deriving

Reported by: mbrodersen Owned by:
Priority: normal Milestone:
Component: Compiler Version: 7.4.1
Keywords: Cc:
Operating System: Linux Architecture: x86
Type of failure: Compile-time crash Difficulty:
Test Case: Blocked By:
Blocking: Related Tickets:

Description

Compiling the following:


module Main where

data Tree a = Edge a | Node (Tree a) (Tree a)

deriving (eq,show)

main10 = print $ Node (Edge 10) (Edge 20)

main = main10


Results in:


ghc: panic! (the 'impossible' happened)

(GHC version 7.4.1 for i386-unknown-linux):

nameModule eq{tv a9O}

Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug


Change History (1)

comment:1 Changed 20 months ago by guest

  • Resolution set to duplicate
  • Status changed from new to closed

It is fixed in HEAD. See ticket #5961. Now you get

Bb.hs:3:57:
    Illegal deriving item `eq'
    In the data declaration for `Tree'
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