[GHC] #10650: Can't define GHCi :def macro with NoImplicitPrelude on

17 Jul 2015


      #10650: Can't define GHCi :def macro with NoImplicitPrelude on
-------------------------------------+-------------------------------------
              Reporter:              |             Owner:
  RyanGlScott                        |            Status:  new
                  Type:  bug         |         Milestone:
              Priority:  normal      |           Version:  7.10.1
             Component:  GHCi        |  Operating System:  Unknown/Multiple
              Keywords:              |   Type of failure:  GHC rejects
          Architecture:              |  valid program
  Unknown/Multiple                   |        Blocked By:
             Test Case:              |   Related Tickets:  #8640
              Blocking:              |
Differential Revisions:              |
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 GHCi is unusually prohibitive in typechecking {{{:def}}} macros when
 {{{NoImplicitPrelude}}} is enabled. Here's an example to illustrate what I
 mean:

 {{{
 $ ghci -XNoImplicitPrelude
 GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
 λ> :def pf \str -> Prelude.return Prelude.$ ":! pointfree \"" Prelude.++
 str Prelude.++ "\""

 <interactive>:1:111:
     Not in scope: type constructor or class ‘String’

 <interactive>:1:121: Not in scope: type constructor or class ‘IO’

 <interactive>:1:124:
     Not in scope: type constructor or class ‘String’
 }}}

 I can understand the functions being out-of-scope when
 {{{NoImplicitPrelude}}} is on, but the type errors don't make any sense to
 me, especially since {{{:t}}} seems to pick up on the types just fine:

 {{{
 λ> :t Prelude.return
 Prelude.return :: GHC.Base.Monad m => a -> m a
 λ> :t "\""
 "\"" :: [GHC.Types.Char]
 }}}

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10650
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