[commit: ghc] master: fix #5022: polymorphic definitions inside arrow rec (4c8e030)

[Ross Paterson]

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/4c8e03075ab8719f3753c1a2e4f05ef21be193ac

>---------------------------------------------------------------

commit 4c8e03075ab8719f3753c1a2e4f05ef21be193ac
Author: Ross Paterson <ross at soi.city.ac.uk>
Date:   Mon Dec 19 23:44:33 2011 +0000

    fix #5022: polymorphic definitions inside arrow rec
    
    This is quite tricky, with examples like this:
    
    import Control.Arrow
    
    pRepeat :: a -> [a]
    pRepeat =
        proc x -> do
          rec
            s <- returnA -< f_rec x:s       -- f_rec is monomorphic here
            let f_later y = y               -- f_later is polymorphic here
            _ <- returnA -< (f_later True, f_later 'a')
            let f_rec y = y                 -- f_rec is polymorphic here
          returnA -< f_later s              -- f_later is monomorphic here
    
    Fixed the typechecking of arrow RecStmt to track changes to the monad
    version.  It was simplest to add a field recS_later_rets corresponding
    to recS_rec_rets.  It's only used for the arrow version, and always
    empty for the monad version.  But I think it would be cleaner to put
    the rec_ids and later_ids in a single list with supplementary info
    saying how they're used.
    
    Also fixed several glitches in the desugaring of arrow RecStmt.  The fact
    that the monomorphic variables shadow their polymorphic counterparts is a
    major pain.  Also a bit of general cleanup of DsArrows while I was there.

 compiler/deSugar/DsArrows.lhs    |  238 +++++++++++++++++++++++---------------
 compiler/hsSyn/HsExpr.lhs        |    9 +-
 compiler/hsSyn/HsUtils.lhs       |    2 +-
 compiler/typecheck/TcArrows.lhs  |   27 +++--
 compiler/typecheck/TcHsSyn.lhs   |    9 +-
 compiler/typecheck/TcMatches.lhs |    3 +-
 6 files changed, 174 insertions(+), 114 deletions(-)


Diff suppressed because of size. To see it, use:

    git show 4c8e03075ab8719f3753c1a2e4f05ef21be193ac