[GHC] #8150: Foreign export requires redundant type signature

[GHC]

#8150: Foreign export requires redundant type signature
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        Reporter:  evincarofautumn   |                   Owner:
            Type:  feature request   |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.6.3
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Incorrect         |  Unknown/Multiple
  warning at compile-time            |               Test Case:
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by rwbarton):

 The types aren't actually required to be the ''same'', though, as this is
 accepted too (even with `-Wall`):

 {{{
 module FFITest where

 foreign export ccall "function"
   function :: IO ()
 function :: IO a
 function = undefined
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8150#comment:2>
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