#9968: DeriveAnyClass fails on multi-parameter type classes -------------------------------------+------------------------------------- Reporter: goldfire | Owner: Type: bug | Status: new Priority: normal | Milestone: 7.10.1 Component: Compiler | Version: 7.10.1-rc1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Blocked By: Test Case: | Related Tickets: Blocking: | Differential Revisions: | -------------------------------------+------------------------------------- When I say {{{ {-# LANGUAGE DeriveAnyClass, MultiParamTypeClasses #-} module Bug where class C a b data X deriving (C Int) }}} and load that into GHCi, I see this: {{{ *Main> :load "/Users/rae/temp/DeriveAny.hs" [1 of 1] Compiling Bug ( /Users/rae/temp/DeriveAny.hs, interpreted ) Var/Type length mismatch: [b_a2YW] [] Var/Type length mismatch: [b_a2YW] [] Ok, modules loaded: Bug. *Bug> :info C class C a b -- Defined at /Users/rae/temp/DeriveAny.hs:5:1 instance C X -- Defined at /Users/rae/temp/DeriveAny.hs:7:13 }}} It seems my `Int` parameter to `C` is being dropped. I don't believe I have a debug build in this example, so that debugging output is shipping. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9968 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler