[GHC] #13060: Visible type application doesn't work for functions with inferred types

3 Jan 2017


      #13060: Visible type application doesn't work for functions with inferred types
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           Reporter:  Feuerbach      |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
  (Type checker)                     |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  GHC rejects
  Unknown/Multiple                   |  valid program
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 {{{
 GHCi, version 8.0.1: http://www.haskell.org/ghc/  :? for help
 Loaded GHCi configuration from /home/feuerbach/.ghci
 Prelude> :set -XTypeApplications -fprint-explicit-kinds -fprint-explicit-
 foralls
 Prelude> :t id
 id :: forall {a}. a -> a
 Prelude> :t id @Int
 id @Int :: Int -> Int
 Prelude> let foo :: a -> a; foo = id
 Prelude> :t foo
 foo :: forall {a}. a -> a
 Prelude> :t foo @Int
 foo @Int :: Int -> Int
 Prelude> let bar = id
 Prelude> :t bar
 bar :: forall {a}. a -> a
 Prelude> :t bar @Int

 <interactive>:1:1: error:
     • Cannot apply expression of type ‘a0 -> a0’
       to a visible type argument ‘Int’
     • In the expression: bar @Int
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13060
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