#5498: Generalized newtype deriving allows creating of instances I can't create by hand -------------------------------------+------------------------------------ Reporter: dterei | Owner: Type: bug | Status: closed Priority: normal | Milestone: 7.6.2 Component: Compiler | Version: 7.3 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Unknown/Multiple Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: 1496 Blocking: | Related Tickets: -------------------------------------+------------------------------------ Changes (by nomeata): * status: new => closed * resolution: => fixed Comment: This should not be possible any more: In the type `intIso :: forall c. c t -> c Int`, `c`’s type parameter is considered to be nominal, so `coerce` will not allow changing `c (Down a)` to `c a` any more. And GND is now based on `Coercible`... -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/5498#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler