#3330: Type checker hangs
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Reporter: MartijnVanSteenbergen | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.10.3
Severity: normal | Resolution:
Keywords: | Testcase:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
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Comment (by MartijnVanSteenbergen):
I'm afraid that will take me a significant amount of time. :-(
What I've done instead is change the example to be independent of
multirec, moving some definitions into the snippet. I've also tried to
make it smaller, removing some function arguments, type arguments and
class constraints and replacing definitions by undefined. In what is left
I cannot find anything else I can remove without causing GHC not to hang
anymore.
{{{
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TypeFamilies #-}
import Control.Monad.Writer
data AnyF (s :: * -> *) = AnyF
class HFunctor (f :: (* -> *) -> * -> *)
type family PF (phi :: * -> *) :: (* -> *) -> * -> *
children :: s ix -> (PF s) r ix -> [AnyF s]
children p x = execWriter (hmapM p collect x)
collect :: HFunctor (PF s) => s ix -> r ix -> Writer [AnyF s] (r ix)
collect = undefined
hmapM :: (forall ix. phi ix -> r ix -> m (r' ix))
-> phi ix -> f r ix -> m (f r' ix)
hmapM = undefined
}}}
Does that help?
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3330#comment:3>
GHC <http://www.haskell.org/ghc/>
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