[GHC] #11126: Entered absent arg in a Repa program

[GHC]

#11126: Entered absent arg in a Repa program
-------------------------------------+-------------------------------------
           Reporter:  tuplanolla     |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  Incorrect result
  Unknown/Multiple                   |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Consider the following program.

 {{{#!hs
 module Main where

 import Data.Array.Repa

 data Stuff = !(Array U DIM1 Double) `With` !Double deriving Show

 through :: Maybe Double -> Stuff -> Stuff
 m `through` (a `With` _) =
   let b = a +^ (negate `smap` sumS (extend (Z :. All :. (1 :: Int)) a))
       c = maybe b (const (negate `smap` a)) m in
       computeUnboxedS c `With` sumAllS b

 main :: IO ()
 main = print $ Just 1 `through` (fromListUnboxed (Z :. 1) [1] `With` 1)
 }}}

 It should produce the following result once run.

 {{{#!hs
 AUnboxed (Z :. 1) (fromList [-1.0]) `With` 0.0
 }}}

 However, when built using `repa-3.4.0.1` and compiled with the options
 `-O3 -Wall -funfolding-keeness-factor1000 -funfolding-use-threshold1000`,
 it crashes as follows.

 {{{#!hs
 Main: Oops!  Entered absent arg arr2 Array D DIM1 Double
 }}}

 Adding `-fno-strictness` to the compiler options or
 removing strictness annotations from the code makes the problem disappear,
 so
 this looks like a strictness analyzer problem.

 The libraries used were

 * `QuickCheck-2.8.1`,
 * `array-0.5.1.0`,
 * `base-4.8.1.0`,
 * `bytestring-0.10.6.0`,
 * `containers-0.5.6.2`,
 * `deepseq-1.4.1.1`,
 * `ghc-prim-0.4.0.0`,
 * `integer-gmp-1.0.0.0`,
 * `pretty-1.1.2.0`,
 * `primitive-0.6`,
 * `random-1.1`,
 * `repa-3.4.0.1`,
 * `template-haskell-2.10.0.0`,
 * `tf-random-0.5`,
 * `time-1.5.0.1`,
 * `transformers-0.4.2.0` and
 * `vector-0.10.12.3`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11126>
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