#7809: Silly error message suggesting LiberalTypeSynonyms -----------------------------+---------------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Component: Compiler Version: 7.7 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- The following code (rightly) does not compile: {{{ {-# LANGUAGE RankNTypes, TypeFamilies, LiberalTypeSynonyms #-} type PolyId = (forall a. a -> a) type family F a foo :: F PolyId foo = undefined }}} The error message is {{{ Illegal polymorphic or qualified type: PolyId Perhaps you intended to use -XLiberalTypeSynonyms In the type signature for `foo': foo :: F PolyId }}} The code doesn't compile because we can't apply a type family to a polytype. The first line of the error message says this well enough, though more information might be helpful here. However, the second line of the error message is silly: I've turned on {{{LiberalTypeSynonyms}}}! -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7809 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler