#7252: Impossible error when deriving lower-cased type class (nameModule show{tv
a9Y})
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Reporter: sfogarty | Owner:
Type: bug | Status: new
Priority: normal | Component: Compiler
Version: 7.4.2 | Keywords:
Os: Linux | Architecture: x86_64 (amd64)
Failure: Compile-time crash | Testcase:
Blockedby: | Blocking:
Related: |
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I had a student who incorrectly typed 'deriving (show)' instead of
'deriving (Show)', and got a very interesting error, as shown below. It
happens in both ghc and ghci. The file should of course be rejected, but
perhaps with a different error message.
$ cat Bug.hs
module Types where
data FuelEfficiency = MPG Float | LPHK Float deriving (show)
$ ghc Bug.hs
[1 of 1] Compiling Types ( Bug.hs, Bug.o )
ghc: panic! (the 'impossible' happened)
(GHC version 7.4.2 for x86_64-unknown-linux):
nameModule show{tv a9Y}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7252>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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