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  • #7384

Closed
Open
Opened Nov 02, 2012 by Richard Eisenberg@raeDeveloper

Panic "ctEvTerm" when using functional dependencies and PolyKinds

The following code causes a panic:

{-# LANGUAGE FunctionalDependencies, PolyKinds #-}

class Baz a b | a -> b where
  bar :: a -> ()

instance Baz Bool Bool where
  bar _ = ()

foo = bar False

The panic reads:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.7.20121031 for x86_64-apple-darwin):
	ctEvTerm: derived constraint cannot have id
<<details unavailable>>

The panic does not happen without -XPolyKinds.

Trac metadata
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Version 7.7
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
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Reference: ghc/ghc#7384