Interesting example, right on the borderline. I've jiggled the type inference for applications a bit so that it works (HEAD only of course). Thanks for the test case. Simon | -----Original Message----- | From: Ashley Yakeley [mailto:ashley@semantic.org] | Sent: 19 March 2003 09:43 | To: glasgow-haskell-users@haskell.org | | This should compile, shouldn't it? | | -- ghc -c -fglasgow-exts TestInfer.hs | module TestInfer where | { | class C t a b | t a -> b; | instance C Char a Bool; | | data P t a = forall b. (C t a b) => MkP b; | | data Q t = MkQ (forall a. P t a); | | f' :: Q Char; | f' = MkQ (MkP True :: forall a. P Char a); | | f :: Q Char; | f = MkQ (MkP True); | } | | GHC 5.04.2 for MacOS X complains about f, but not about f': | | TestInfer.hs:15: | Could not deduce (C t a Bool) from the context () | Probable fix: | Add (C t a Bool) to the When generalising the type of an | expression | Or add an instance declaration for (C t a Bool) | arising from use of `MkP' at TestInfer.hs:15 | In the first argument of `MkQ', namely `(MkP True)' | In the definition of `f': MkQ (MkP True) | | -- | Ashley Yakeley, Seattle WA | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users@haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users