#14220: GeneralizedNewtypeDeriving and polymorphic arguments don't play nicely together ---------------------------------+-------------------------------------- Reporter: ivanm | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.2 Resolution: | Keywords: Operating System: MacOS X | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | ---------------------------------+-------------------------------------- Comment (by Iceland_jack): Doesn't panic for 8.0.1 {{{ $ ghci -ignore-dot-ghci /tmp/a.hs GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( /tmp/a.hs, interpreted ) /tmp/a.hs:10:13: Could not coerce from ‘proxy Int’ to ‘proxy MyInt’ because ‘proxy Int’ and ‘proxy MyInt’ are different types. arising from the coercion of the method ‘nameOf’ from type ‘forall (proxy :: * -> *). proxy Int -> String’ to type ‘forall (proxy :: * -> *). proxy MyInt -> String’ Possible fix: use a standalone 'deriving instance' declaration, so you can specify the instance context yourself When deriving the instance for (NameOf MyInt) Failed, modules loaded: none. Prelude> }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14220#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler