[GHC] #9497: Silent typed holes

[GHC]

#9497: Silent typed holes
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              Reporter:  merijn      |            Owner:
                  Type:  feature     |           Status:  new
  request                            |        Milestone:
              Priority:  normal      |          Version:  7.8.3
             Component:  Compiler    |         Keywords:  typed holes,
            Resolution:              |  warnings
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by simonpj):

 Crumbs, you are right.  I'd forgotten that we'd decided ''not'' to make
 typed holes into a language extension (see
 [http://www.haskell.org/pipermail/ghc-devs/2014-January/003758.html this
 email]), but rather controlled by `-fwarn-typed-holes` which is on by
 default.

 I agree with Richard that this is jolly confusing.

 Two issues with Richard's proposals:

  * There is no way to switch off typed holes altogether, and revert to
 {{{
 Hole.hs:1:7: Pattern syntax in expression context: _
 }}}
  Maybe that is OK.

  * What does `-fno-warn-typed-holes` do in the absence of `-fdefer-typed-
 holes`?  No-op with a warning?

  * What does `-fwarn-typed-holes` do?  Perhaps just re-enable the warning
 after switching off all warnings with `-w`.

 Modulo just specifying (and documenting) this behaviour, I'd be content
 with the above.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9497#comment:4>
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