#8631: Need ImpredicativeTypes for GeneralizedNewtypeDeriving? -------------------------------------+------------------------------------ Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by simonpj): * cc: sweirich@… (added) Comment: We really want explicit type application here (#4466, #5296). The point is that we want to say "instantiate `coerce` at these particular types", which happen in this case to be polymorphic. (There is a good reason to be suspicious about filling in unification variables with polytypes, but explicit type application would mean that didn't happen.) Stephanie has a student working on this, I believe. Simon -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8631#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler