[GHC] #11715: Constraint vs *

GHC ghc-devs at haskell.org
Fri Aug 19 11:58:03 UTC 2016


#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 goldfire):

 Yes, that's true, but this is just the situation with
 `IncoherentInstances`, where specializing a type changes the meaning of an
 expression. Normally, we can assign an expression a more specific type at
 will. In this case, if we try to assign `foo` the more specific type `Int
 -> Int -> (Int => r) -> r`, we will get a duplicate-`with` error.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11715#comment:22>
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