id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	os	architecture	failure	difficulty	testcase	blockedby	blocking	related
1797	type equality test leads to a looping type checker	guest	igloo	"The following code (similar to one of HList’s generic type equality tests) causes GHC to loop forever (or at least very long) with GHC 6.8.0.20071020 on i386-unknown-mingw32 and GHC 6.8.0.20071019 on i386-unknown-linux:
{{{
{-# LANGUAGE
    MultiParamTypeClasses,
    FunctionalDependencies,
    UndecidableInstances,
    OverlappingInstances,
    FlexibleInstances,
    EmptyDataDecls #-}

data True

data False

class TypeEq type1 type2 result | type1 type2 -> result where
    typeEq :: type1 -> type2 -> result

instance TypeEq soleType soleType True where
    typeEq _ _ = undefined

instance (TypeCast False result) => TypeEq type1 type2 result where
    typeEq _ _ = undefined

class TypeCast type1 type2 | type1 -> type2, type2 -> type1

instance TypeCast soleType soleType
}}}"	merge	closed	normal		Compiler	6.8	fixed		g9ks157k@…	Unknown/Multiple	x86		Unknown	FD4