[GHC] #7068: Extensive Memory usage (regression)

[GHC]

#7068: Extensive Memory usage (regression)
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        Reporter:  waldheinz                     |            Owner:
            Type:  bug                           |  simonpj
        Priority:  high                          |           Status:  new
       Component:  Compiler                      |        Milestone:  7.8.3
      Resolution:                                |          Version:  7.4.1
Operating System:  Unknown/Multiple              |         Keywords:
 Type of failure:  Compile-time performance bug  |     Architecture:
       Test Case:                                |  Unknown/Multiple
        Blocking:                                |       Difficulty:
                                                 |  Unknown
                                                 |       Blocked By:
                                                 |  Related Tickets:
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Comment (by George):

 When I try to reproduce on ghc 7.8.1 and Vec-1.0.1 with pcapriotti's
 instructions above I get a compilation error:

 {{{
  ghc -fforce-recomp --make -O1 Data/Vec/LinAlg.hs -fspec-constr
 [1 of 3] Compiling Data.Vec.Nat     ( Data/Vec/Nat.hs, Data/Vec/Nat.o )
 [2 of 3] Compiling Data.Vec.Base    ( Data/Vec/Base.hs, Data/Vec/Base.o )
 [3 of 3] Compiling Data.Vec.LinAlg  ( Data/Vec/LinAlg.hs,
 Data/Vec/LinAlg.o )

 Data/Vec/LinAlg.hs:241:10:
     Illegal instance declaration for ‘SetDiagonal v m’
       The liberal coverage condition fails in class ‘SetDiagonal’
         for functional dependency: ‘m -> v’
       Reason: lhs type ‘m’ does not determine rhs type ‘v’
     In the instance declaration for ‘SetDiagonal v m’

 Data/Vec/LinAlg.hs:580:10:
     Illegal instance declaration for ‘Pivot a (() :. v)’
       The liberal coverage condition fails in class ‘Pivot’
         for functional dependency: ‘m -> a’
       Reason: lhs type ‘() :. v’ does not determine rhs type ‘a’
     In the instance declaration for ‘Pivot a (() :. v)’
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7068#comment:11>
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