#1965: Allow unconstrained existential contexts in newtypes -------------------------------------+------------------------------------ Reporter: guest | Owner: Type: feature request | Status: new Priority: normal | Milestone: 7.6.2 Component: Compiler | Version: 6.8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Comment (by pumpkin): To be clear about what I'm looking for: {{{ #!haskell data IntList where Nil :: IntList Cons :: Int -> IntList -> IntList data Nat = Z | S Nat data IntVec :: Nat -> * where NilV :: IntVec Z ConsV :: Int -> IntVec n -> IntVec (S n) -- N.B: not data newtype Exists (f :: k -> *) = forall x. Exists (f x) type IntVecList = Exists IntVec -- IntVec and IntVecList should be isomorphic! If Exists can't be a newtype, I have to pay a penalty for adding indices to my type :( }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/1965#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler