Re: [GHC] #10249: GHCi leaky abstraction: error message mentions `ghciStepIO`

22 Oct 2015

      #10249: GHCi leaky abstraction: error message mentions `ghciStepIO`
-------------------------------------+-------------------------------------
        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.1
       Component:  GHCi              |              Version:  7.10.1
      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 Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bgamari):

 * failure:  None/Unknown => Incorrect warning at compile-time
 * milestone:   => 8.0.1

Old description:
...
{{{#!hs
$ ghci -fdefer-type-errors -ignore-dot-ghci
GHCi, version 7.10.0.20150316: http://www.haskell.org/ghc/  :? for help
Prelude> _
<interactive>:2:1: Warning:
    Found hole ‘_’ with type: IO t0
    Where: ‘t0’ is an ambiguous type variable
    In the first argument of ‘GHC.GHCi.ghciStepIO ::
                                IO a_aly -> IO a_aly’, namely
      ‘_’
    In a stmt of an interactive GHCi command:
      it <- GHC.GHCi.ghciStepIO :: IO a_aly -> IO a_aly _
*** Exception: <interactive>:2:1:
    Found hole ‘_’ with type: IO t0
    Where: ‘t0’ is an ambiguous type variable
    In the first argument of ‘GHC.GHCi.ghciStepIO ::
                                IO a_aly -> IO a_aly’, namely
      ‘_’
    In a stmt of an interactive GHCi command:
      it <- GHC.GHCi.ghciStepIO :: IO a_aly -> IO a_aly _
(deferred type error)
Prelude>
}}}
It should ideally not expose `ghciStepIO` to the user.
New description:

 {{{
 $ ghci -fdefer-type-errors -ignore-dot-ghci
 GHCi, version 7.10.0.20150316: http://www.haskell.org/ghc/  :? for help
 Prelude> _

 <interactive>:2:1: Warning:
     Found hole ‘_’ with type: IO t0
     Where: ‘t0’ is an ambiguous type variable
     In the first argument of ‘GHC.GHCi.ghciStepIO ::
                                 IO a_aly -> IO a_aly’, namely
       ‘_’
     In a stmt of an interactive GHCi command:
       it <- GHC.GHCi.ghciStepIO :: IO a_aly -> IO a_aly _
 *** Exception: <interactive>:2:1:
     Found hole ‘_’ with type: IO t0
     Where: ‘t0’ is an ambiguous type variable
     In the first argument of ‘GHC.GHCi.ghciStepIO ::
                                 IO a_aly -> IO a_aly’, namely
       ‘_’
     In a stmt of an interactive GHCi command:
       it <- GHC.GHCi.ghciStepIO :: IO a_aly -> IO a_aly _
 (deferred type error)
 Prelude>
 }}}

 It should ideally not expose `ghciStepIO` to the user.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10249#comment:4
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