[GHC] #11352: Allow applying type to label

4 Jan 2016


      #11352: Allow applying type to label
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  7.10.3
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 {{{#!hs
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE FlexibleContexts      #-}
 {-# LANGUAGE TypeApplications      #-}
 {-# LANGUAGE OverloadedLabels      #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE DataKinds             #-}

 import GHC.TypeLits
 import GHC.OverloadedLabels

 instance IsLabel "answer" Int where
   fromLabel _ = 42

 answer :: IsLabel "answer" a => a
 answer = #answer
 }}}

 The follow works:

 {{{#!hs
...
...
...
answer @Int
 42
 }}}
but fails with a label:

 {{{#!hs
...
...
...
#answer @Int
 <interactive>:...:1: error:
     • Cannot not apply expression of type ‘t0’
       to a visible type argument ‘Int’
     • In the expression: #answer @Int
       In an equation for ‘it’: it = #answer @Int
 }}}
--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11352
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