[GHC] #393: functions without implementations

[GHC]

#393: functions without implementations
-------------------------------------+-------------------------------------
              Reporter:  c_maeder    |            Owner:  simonpj
                  Type:  feature     |           Status:  new
  request                            |        Milestone:  ⊥
              Priority:  normal      |          Version:  None
             Component:  Compiler    |         Keywords:
  (Type checker)                     |     Architecture:  Unknown/Multiple
            Resolution:  None        |       Difficulty:  Moderate (less
      Operating System:              |  than a day)
  Unknown/Multiple                   |       Blocked By:
       Type of failure:              |  Related Tickets:
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 Actually using this
 {{{
 f :: Int -> Int
 f = _           -- Note "_" not "undefined"
 }}}
 plus compiling with `-fdefer-type-errors`, will give a runtime error when
 (and only when) `f` is called, giving file and line number.  See
 [http://www.haskell.org/ghc/docs/latest/html/users_guide/typed-holes.html
 the manual on typed holes].

 See #9497 for making this a bit better.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/393#comment:24>
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