id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc
28,Cannot make existential type instance of class with fundep,guest,nobody,"There seems to be a problem when combining !FunDeps and Existential Types.
The code below (works on ghci) causes an error: 

- ''ERROR ""Existential.hs"":8 - Existentially quantified variable escapes from pattern !FooObj a''. 

{{{
class Foo a b | a -> b where foo :: a -> (String,b)

data FooA = A
instance Foo FooA String where foo _  = (""tyA"",""A-specific"")

data FooObj = forall a b. Foo a b => FooObj a 
instance Foo FooObj () where foo (FooObj a) = (fst (foo a),()) -- !!!
}}}


best regards, benedikt",defect,new,minor,,type system,200605,,,