[GHC] #9913: Discrepancy in type synonym definition and usage

[GHC]

#9913: Discrepancy in type synonym definition and usage
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              Reporter:              |            Owner:
  Iceland_jack                       |           Status:  closed
                  Type:  bug         |        Milestone:
              Priority:  lowest      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:
  (Parser)                           |     Architecture:  x86
            Resolution:  invalid     |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:
       Type of failure:  GHC         |
  rejects valid program              |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by nomeata):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 Thanks for your report.

 I don’t think this is a bug. There is a conceptual difference between the
 declaration, where the argument to the type synonyms are declared (and
 hence have to be variables), and the use of a type synonym, where
 parameters are type expressions.

 Note that you can use `Alg Maybe`, but cannot define `type Alg Maybe a =
 Maybe a -> a`.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9913#comment:1>
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