[GHC] #10794: Extension request: "where" clauses in type signatures

[GHC]

#10794: Extension request: "where" clauses in type signatures
-------------------------------------+-------------------------------------
        Reporter:  danso             |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  lowest            |               Milestone:
       Component:  Compiler (Type    |                 Version:  7.10.2
  checker)                           |
      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 danso):

 Replying to [comment:1 nomeata]:
 > {{{#!hs
 > fold :: f -> [a] -> a
 >         where f :: a -> a -> a
 > }}}
 > is certainly confusing, because in the first line `f` is used like a
 type, but in the second, `f` is used like a value (or `a -> a -> a` is
 used like a kind
 >
 > Maybe you meant
 > {{{#!hs
 > fold :: f -> [a] -> a
 >         where f = a -> a -> a
 > }}}
 > which could be extended to allow
 >
 > {{{#!hs
 > fold :: f -> [a] -> a
 >         where f :: *
 >               f = a -> a -> a
 > }}}
 >
 > I’m sure the type level programming wizards and dependently typed
 programmers will have the greatest need for such an extension, and have a
 good opinion here.

 Good catch. I agree that your suggestion makes more sense and have changed
 the ticket accordingly.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10794#comment:3>
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