[GHC] #11715: Constraint vs *

[GHC]

#11715: Constraint vs *
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  high              |            Milestone:  8.2.1
       Component:  Compiler (Type    |              Version:  8.0.1-rc1
  checker)                           |
      Resolution:                    |             Keywords:  Typeable
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by int-index):

 Replying to [comment:32 simonpj]:

 This should work, although I would prefer to have `incoherentWith` at my
 disposal as well, for cases when I'm willing to manually ensure that in
 any local scope only one value is available. Consider this case:

 {{{
 module M (f) where

 f :: Int -> ...
 helper1 :: Int => ...
 helper2 :: Int => ...
 }}}

 Here I'd like to pass `Int` to the helpers using `incoherentWith`, but
 since only `f` is exported, the unsafety is contained within the module
 boundaries.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11715#comment:33>
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