[GHC] #15114: ghc 8.4.1 lifts errors out of if then else

[GHC]

#15114: ghc 8.4.1 lifts errors out of if then else
-------------------------------------+-------------------------------------
        Reporter:  elaforge          |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by simonpj):

 Thanks. That makes me sure it relates to #5129.

 Don't worry, I'll add it as a regression test myself, shortly.  Thanks for
 boiling it down.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15114#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler