Opened 5 years ago

Closed 5 years ago

#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 Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


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:

Change History (1)

comment:1 Changed 5 years ago by guest

Resolution: duplicate
Status: newclosed

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

    Illegal deriving item `eq'
    In the data declaration for `Tree'
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