[GHC] #14973: Location in GHCi debugger prompt printed twice when default prompt is used

[GHC]

#14973: Location in GHCi debugger prompt printed twice when default prompt is used
-------------------------------------+-------------------------------------
           Reporter:  osa1           |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  GHCi           |           Version:  8.5
           Keywords:  debugger       |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 (Noticed in #8316)

 Test.hs:

 {{{#!haskell
 foo :: [Int]
 foo = [ 1 .. 10 ]
 }}}

 Reproducer:

 {{{
 $ ghc-stage2 --interactive -ignore-dot-ghci Test.hs
 GHCi, version 8.5.20180325: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Test.hs, interpreted )
 Ok, one module loaded.
 *Main> :break foo
 Breakpoint 0 activated at Test.hs:2:7-14
 *Main> foo
 Stopped in Main.foo, Test.hs:2:7-14
 _result :: [Int] = _
 [Test.hs:2:7-14] [Test.hs:2:7-14] *Main>
 }}}

 The `[Test.hs:2:7-14]` part is repeated. Setting the prompt fixes it:

 {{{
 $ ghc-stage2 --interactive Test.hs -ignore-dot-ghci
 GHCi, version 8.5.20180325: http://www.haskell.org/ghc/  :? for help
 [1 of 1] Compiling Main             ( Test.hs, interpreted )
 Ok, one module loaded.
 *Main> :set prompt "> "
 > :break foo
 Breakpoint 0 activated at Test.hs:2:7-14
 > foo
 Stopped in Main.foo, Test.hs:2:7-14
 _result :: [Int] = _
 [Test.hs:2:7-14] >
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14973>
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