id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
7384,"Panic ""ctEvTerm"" when using functional dependencies and PolyKinds",goldfire,,"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}}}.",bug,closed,normal,,Compiler,7.7,fixed,FunctionalDependencies PolyKinds,,Unknown/Multiple,Unknown/Multiple,None/Unknown,Unknown,typecheck/should_compile/T7384,,,