[GHC] #15392: Inconsistency in parsing trailing commas inside import section

16 Jul 2018

      #15392: Inconsistency in parsing trailing commas inside import section
-------------------------------------+-------------------------------------
           Reporter:  chshersh       |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.3
  (Parser)                           |
           Keywords:                 |  Operating System:  Unknown/Multiple
  imports,trailing,commas            |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 The following Haskell code compiles without problems:

 {{{#!hs
 import Data.Bool (Bool,)
 }}}

 As I understand, trailing commas are allowed at the end of `import`
 declaration. But if I have trailing comma inside data type import part, I
 see parse error:

 {{{#!hs
 import Data.Bool (Bool (True,))
 }}}

 I don't see why this code is forbidden. But allowing trailing commas
 inside parts of data type imports will make support for automatic
 refactoring tools easier since they don't need to care about this special
 case for removing trailing comma manually.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15392
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