[GHC] #15034: Desugaring `mdo` moves a `let` where it shouldn't be

[GHC]

#15034: Desugaring `mdo` moves a `let` where it shouldn't be
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        Reporter:  parsonsmatt       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.2.2
      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:                    |
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Comment (by simonpj):

 >  Looking at the ​Haskell Prime wiki entry for Recursive Do, this seems
 to be the relevant bit: That is, a variable used before it is bound is
 treated as recursively defined, while in a Haskell 98 do-statement it
 would be treated as shadowed.

 So it looks as if GHC is following the specification.  Are you proposing a
 different specification?  And if so, what is it?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15034#comment:1>
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