[GHC] #10867: Primop types should not mention ()

[GHC]

#10867: Primop types should not mention ()
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        Reporter:  simonpj           |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.10.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by simonmar):

 The RTS refers to lots of things that are defined in Haskell,
 incidentally, not just in primops.  The full list is in `rts/Prelude.h`.

 But you can change these primops if necessary.  You probably didn't find
 the implementations because they're Z-encoded; `finalizeWeak#` is
 `stg_finalizzeWeakzh` in `rts/PrimOps.h`.  It returns the finalizer of a
 weak pointer, which has type `State# RealWorld -> (# State# RealWorld, ()
 #)`, but you could always lie and give it a more general type.  The
 wrapper in `GHC.Weak` will probably work unchanged.  We already lie in the
 type of `mkWeak#` in a similar way, for reasons I forget.

 It looks like `check#` has the wrong type anyway, its implementation
 returns `()` (ie. zero return values in Cmm), so its Haskell type should
 have a return type of `State# RealWorld`.  Feel free to change its name at
 the same time, I agree it's a silly name!  When changing this you'll need
 to run the tests in the stm package, which I think aren't run by default.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10867#comment:9>
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