[GHC] #9190: Iface type variable out of scope: s

[GHC]

#9190: Iface type variable out of scope:  s
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        Reporter:  nomeata           |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.9
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by nomeata):

 I managed to extract a smaller example exhibiting the problem:

 {{{
 module T9190 (pfxSumR) where

 import Numeric.Sum
 import qualified Data.Vector.Generic as G
 import qualified Data.Vector.Unboxed as U

 pfxSumR :: U.Vector Double -> U.Vector Double
 pfxSumR = G.map kbn . G.scanr (flip add) zero
 }}}

 The problem only occurs with `-O`, and would not occur with

 {{{
 -- No error with:
 -- pfxSumR :: U.Vector KBNSum -> U.Vector Double
 -- pfxSumR = G.map kbn . G.scanr (flip add) zero
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9190#comment:1>
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