#13335: Non-abstract types also have skolem nature -------------------------------------+------------------------------------- Reporter: ezyang | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.1 Component: Compiler | Version: 8.1 (Type checker) | Keywords: backpack | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In #12680, we determined that abstract types from signatures need to be treated like skolem variables. But it turns out other types from signatures also need to be treated like skolem variables too: {{{ {-# LANGUAGE GADTs #-} unit p where signature M1 where data A = MkA signature M2 where data A = MkA module A where import qualified M1 import qualified M2 f :: M1.A ~ M2.A => a -> b f x = x }}} This is bad because these As could be the same thing in the end. I think the real, final fix, is to not test for "skolem abstractness" (as we do now), but just look and see if the Name for the TyCon is a name hole or not. Then we can eliminate skolem abstract completely. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13335 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler