[GHC] #13056: Deriving Foldable causes GHC to take a long time (GHC 8.0 ONLY)

2 Jan 2017

      #13056: Deriving Foldable causes GHC to take a long time (GHC 8.0 ONLY)
-------------------------------------+-------------------------------------
           Reporter:  ezyang         |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2-rc2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  performance bug
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 This file never finishes compiling on GHC 8.0.1, and GHC 8.0.2 (dated
 20161213):

 {{{
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveFoldable #-}

 module Bug where
 import Data.Typeable
 import GHC.Generics
 import Data.Data

 data Condition v = Condition
     deriving (Functor, Foldable)

 data CondTree v c a = CondNode
     { condTreeData        :: a
     , condTreeConstraints :: c
     , condTreeComponents  :: [CondBranch v c a]
     }
     deriving (Functor, Foldable)

 data CondBranch v c a = CondBranch
     { condBranchCondition :: Condition v
     , condBranchIfTrue    :: CondTree v c a
     , condBranchIfFalse   :: Maybe (CondTree v c a)
     }
     deriving (Functor, Foldable)
 }}}

 The problem seems to be fixed in HEAD but I haven't looked for the commit
 that fixed it.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13056
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