[GHC] #4851: NoImplicitPrelude does not handle rec / mfix / ArrowLoop properly

[GHC]

#4851: NoImplicitPrelude does not handle rec / mfix / ArrowLoop properly
---------------------------------+------------------------------------------
    Reporter:  peteg             |       Owner:                           
        Type:  bug               |      Status:  new                      
    Priority:  normal            |   Component:  Compiler                 
     Version:  6.12.3            |    Keywords:                           
    Testcase:                    |   Blockedby:                           
          Os:  Unknown/Multiple  |    Blocking:                           
Architecture:  Unknown/Multiple  |     Failure:  GHC rejects valid program
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 Consider this program:

 {{{
 {-# LANGUAGE Arrows, NoImplicitPrelude #-}
 module T where

 import Prelude hiding ( id, (.) )

 import Control.Category ( Category(..) )
 import Control.Arrow

 garbage =
   proc b ->
     do rec (c, d) <- undefined -< (b, d)
        returnA -< c
 }}}
 I think this is the new idiomatic way of writing Arrow code due to the use
 of Category, which clashes with the Prelude. I wish to avoid the explicit
 "import Prelude hiding..." stuff in all the other modules.

 In GHC 6.12.3 this gives an error about mfix.

 Removing NoImplicitPrelude yields an error about ArrowLoop, as expected.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4851>
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