[GHC] #14421: LambdaCase should be suggested if it is used but not enabled

[GHC]

#14421: LambdaCase should be suggested if it is used but not enabled
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           Reporter:  tomjaguarpaw   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           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:
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 If I try to make a multiparameter typeclass GHC (well, GHCi here) advises
 me to turn on {{{MultiParamTypeClasses}}}

 {{{
 Prelude> class C a b where
 ...
   (Use MultiParamTypeClasses to allow multi-parameter classes)
 }}}

 But if I try to use {{{\case}}} it doesn't give me a helpful suggestion

 {{{
 Prelude> :t \case (_,_) -> ()

 <interactive>:1:2: error: parse error on input ‘case’
 }}}

 Could it?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14421>
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