#9373: typeable instances incompatible between 7.8 and 7.9 -------------------------------------+------------------------------------- Reporter: carter | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.8.2 Keywords: | Operating System: Architecture: Unknown/Multiple | Unknown/Multiple Difficulty: Unknown | Type of failure: Blocked By: | None/Unknown Related Tickets: | Test Case: | Blocking: | Differential Revisions: -------------------------------------+------------------------------------- not sure if this is deliberate or by design, but to get some typeable instances happy for some DataKind heavy code, if i wish it to build in both 7.8 and 7.9, i need to write it in the following form {{{#!hs {-# LANGUAGE DataKinds, GADTs, TypeFamilies, TypeOperators, ConstraintKinds, ScopedTypeVariables, RankNTypes #-} data Nat = S !Nat | Z deriving (Eq,Show,Read,Typeable,Data) #if defined(__GLASGOW_HASKELL__) && ( __GLASGOW_HASKELL__ >= 707) && ( __GLASGOW_HASKELL__ < 709) deriving instance Typeable 'Z deriving instance Typeable 'S #endif }}} if i omit the latter typeables in 7.8, i can't get typeable instances for Nat indexed data types, but i get a GHC error if i include them in 7.9 {{{ Duplicate instance declarations: instance Typeable 'S -- Defined at src/Numerical/Nat.hs:24:28 instance Typeable 'S -- Defined at src/Numerical/Nat.hs:28:1 src/Numerical/Nat.hs:24:28: Duplicate instance declarations: instance Typeable 'Z -- Defined at src/Numerical/Nat.hs:24:28 instance Typeable 'Z -- Defined at src/Numerical/Nat.hs:27:1 }}} https://travis-ci.org/wellposed/numerical/jobs/31011288#L525 for context I can work around it with CPP, but is this a deliberate change or accidental? (i'm ok with that CPP being there, but would like some confirmation this is a deliberate change) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9373 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler