[GHC] #15509: `showEFloat` inconsistency introduced in base-4.12

[GHC]

#15509: `showEFloat` inconsistency introduced in base-4.12
-------------------------------------+-------------------------------------
        Reporter:  hvr               |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.6.1-beta1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5083
       Wiki Page:                    |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"e71e341f87c055ecc01f85ddd8d7a2094dfa8e9a/ghc"
 e71e341f/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="e71e341f87c055ecc01f85ddd8d7a2094dfa8e9a"
 base: showEFloat: Handle negative precisions the same of zero precision

 Test Plan: Validate

 Reviewers: hvr, alpmestan

 Reviewed By: alpmestan

 Subscribers: rwbarton, carter

 GHC Trac Issues: #15509

 Differential Revision: https://phabricator.haskell.org/D5083
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15509#comment:5>
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