Hi, I have stumbled across some strange behaviour in ghc7.
The following compiles fine with ghc 6.12.3: {-# LANGUAGE ImplicitParams #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE NoMonomorphismRestriction #-} module Test where class C t where type TF t ttt :: TF t -> t b :: (C t, ?x :: TF t) => t b = ttt ?x but ghc7 says: Could not deduce (?x::TF t) arising from a use of implicit parameter `?x' from the context (C t, ?x::TF t) bound by the type signature for b :: (C t, ?x::TF t) => t at Test.hs:13:1-10 In the first argument of `ttt', namely `?x' In the expression: ttt ?x In an equation for `b': b = ttt ?x Moreover, when I comment out the type declaration for b, it compiles and the inferred type for b is identical to the one in the above program: *Test> :t b b :: (C t, ?x::TF t) => t It feels to me like a bug but I am not entirely confident. Any ideas? Michal -- |o| Michal Konecny <mikkone...@gmail.com> |o| http://www-users.aston.ac.uk/~konecnym/ |o| office: (+42) (0)121 204 3462 |o| PGP key http://www-users.aston.ac.uk/~konecnym/ki.aston -- |o| Michal Konecny <mikkone...@gmail.com> |o| http://www-users.aston.ac.uk/~konecnym/ |o| office: (+42) (0)121 204 3462 |o| PGP key http://www-users.aston.ac.uk/~konecnym/ki.aston -- |o| Michal Konecny <mikkone...@gmail.com> |o| http://www-users.aston.ac.uk/~konecnym/ |o| office: (+42) (0)121 204 3462 |o| PGP key http://www-users.aston.ac.uk/~konecnym/ki.aston
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