[GHC] #15233: You can always set fixity of (:), with no effect

[GHC]

#15233: You can always set fixity of (:), with no effect
-------------------------------------+-------------------------------------
           Reporter:  Iceland_jack   |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.5
           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:
-------------------------------------+-------------------------------------
 This works in a normal file

 {{{#!hs
 infixl 5 :
 }}}

 or in ghci

 {{{
 $ ghci
 GHCi, version 8.5.20180314: http://www.haskell.org/ghc/  :? for help
 Prelude> infixr 5 :
 Prelude>
 }}}

 and has no effect

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15233>
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