[GHC] #13453: Seemingly can't mix ImplicitParams in where clauses

[GHC]

#13453: Seemingly can't mix ImplicitParams in where clauses
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.1
  (Parser)                           |
           Keywords:                 |  Operating System:  Unknown/Multiple
  ImplicitParams                     |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 These are fine

 {{{#!hs
 v = () where
   a = True
   b = 'a'
 }}}

 {{{#!hs
 v = () where
   ?a = True
   ?b = 'a'
 }}}

 but the moment one of them is an `ImplicitParams` it fails to parse

 {{{#!hs
 -- tAMA.hs:9:3-4: error: Parse error in pattern: ?b
 -- Compilation failed.
 v = () where
   a  = True
   ?b = 'a'

 -- tAMA.hs:9:3: error: parse error on input ‘b’
 -- Compilation failed.
 v = () where
   ?a = True
   b  = 'a'
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13453>
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