Re: [GHC] #14285: Entered absent arg - triggered by INLINEABLE, regression from 8.0.2

27 Sep 2017

      #14285: Entered absent arg - triggered by INLINEABLE, regression from 8.0.2
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        Reporter:  j.waldmann    |                Owner:  (none)
            Type:  bug           |               Status:  new
        Priority:  normal        |            Milestone:
       Component:  Compiler      |              Version:  8.2.1
      Resolution:                |             Keywords:
Operating System:  Linux         |         Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):
       Wiki Page:                |
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Comment (by RyanGlScott):

 By sheer dumb luck, I managed to reduce this down to the following two
 files:

 {{{#!hs
 module Foo where

 import qualified Data.Foldable as F
 import qualified Data.IntMap as IM
 import qualified Data.IntSet as IS
 import Prelude hiding (null)
 import System.Environment

 data Set k = Set IS.IntSet

 null (Set a) = IS.null a

 empty = Set IS.empty

 sfromList :: (Enum a, Foldable c) => c a -> Set a
 sfromList xs = Set $ IS.fromList $ Prelude.map fromEnum $ F.toList xs

 newtype Map k v = Map { unMap :: (IM.IntMap v) } deriving (Eq, Ord)

 {-# inlineable fromList #-}
 fromList :: Enum k => [(k,v)] -> Map k v
 fromList kvs =
   Map $ IM.fromList $ Prelude.map (\(k,v) -> (fromEnum k, v)) kvs

 {-# inlineable findWithDefault #-}
 findWithDefault d k (Map m) = IM.findWithDefault d (fromEnum k) m

 data Rel a b = Rel !(Map a (Set b)) !(Map b (Set a))

 {-# INLINEABLE images #-}
 images x (Rel f b) = findWithDefault empty x f
 {-# INLINEABLE pre_images #-}
 pre_images x rel = images x $ mirrorRel rel
 {-# INLINEABLE mirrorRel #-}
 mirrorRel :: Rel a b -> Rel b a
 mirrorRel (Rel f g) = Rel g f
 }}}

 {{{#!hs
 module Main where

 import Foo
 import Prelude hiding (null)

 main :: IO ()
 main = do
   let args = "hw"
   print $ null $ pre_images 'a' (Rel (fromList [('a',sfromList args)])
 (fromList [('b',sfromList ar
 gs)]))
 }}}

 This works on GHC 8.0.2:

 {{{
 $ /opt/ghc/8.0.2/bin/ghc -O2 -fforce-recomp Main.hs
 [1 of 2] Compiling Foo              ( Foo.hs, Foo.o )
 [2 of 2] Compiling Main             ( Main.hs, Main.o )
 Linking Main ...
 $ ./Main
 True
 }}}

 But not on GHC 8.2.1:

 {{{
 $ /opt/ghc/8.0.2/bin/ghc -O2 -fforce-recomp Main.hs
 [1 of 2] Compiling Foo              ( Foo.hs, Foo.o )
 [2 of 2] Compiling Main             ( Main.hs, Main.o )
 Linking Main ...
 $ ./Main
 True
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14285#comment:4
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