#7642: Nullary type classes -----------------------------+---------------------------------------------- Reporter: shachaf | Owner: Type: feature request | Status: new Priority: normal | Component: Compiler (Type checker) Version: 7.6.1 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: None/Unknown | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- Comment(by monoidal): I strongly support this feature, but another change is needed. {{{ {-# LANGUAGE MultiParamTypeClasses #-} class A where f :: a -> a H.hs:2:1: The class method `f' mentions none of the type variables of the class A When checking the class method: f :: forall a. a -> a In the class declaration for `A' Failed, modules loaded: none. }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7642#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler